Aktuelle Publikationen der Technischen Fakultät

Jahre: 2019 | 2018

2019

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Ujwala P.,, Pentek Q.,, Hein S.,, Miernik A.,, Reiterer A.
Image based 3D reconstruction of the bladder using structure-from-motion – Proof of principle in a phantom model
2019 European Association of Urology
Kurzfassung#AM19-1411
Christoph Scholl, Jie-Hong Roland Jiang, Ralf Wimmer, Aile Ge-Ernst
A PSPACE Subclass of Dependency Quantified Boolean Formulas and Its Effective Solving
2019 33th AAAI Conference on Artificial Intelligence (AAAI-19)
KurzfassungDependency quantified Boolean formulas (DQBFs) are a powerful formalism, which subsumes quantified Boolean formulas (QBFs) and allows an explicit specification of dependencies of existential variables on universal variables. This enables a succinct encoding of decision problems in the NEXPTIME complexity class. As solving general DQBFs is NEXPTIME complete, in contrast to the PSPACE completeness of QBF solving, characterizing DQBF subclasses of lower computational complexity allows their effective solving and is of practical importance. Recently a DQBF proof calculus based on a notion of fork extension, in addition to resolution and universal reduction, was proposed by Rabe in 2017. We show that this calculus is in fact incomplete for general DQBFs, but complete for a subclass of DQBFs, where any two existential variables have either identical or disjoint dependency sets over the universal variables. We further characterize this DQBF subclass to be SigmaP3 complete in the polynomial time hierarchy. Essentially using fork extension, a DQBF in this subclass can be converted to an equisatisfiable 3QBF with only a linear increase in formula size. We exploit this conversion for effective solving of this DQBF subclass and point out its potential as a general strategy for DQBF quantifier localization. Experimental results show that the method outperforms state-of-the-art DQBF solvers on a number of benchmarks, including the 2018 DQBF evaluation benchmarks.
A. Müller, M. C. Wapler, U. Wallrabe
A quick and accurate method to determine the Poisson’s ratio and the coefficient of thermal expansion of PDMS
2019 Soft Matter, Band: 15, Seiten: 779 - 784
Dornhof J, Urban G, Kieninger J
Deposition of Copper Nanofilms by Surface-Limited Redox Replacement of Underpotentially Deposited Lead on Polycrystalline Gold
2019 J Electrochem Soc, Band: 166, Nummer: 1, Seiten: D3001 - D3005
KurzfassungElectrochemical atomic layer deposition (E-ALD) of copper on polycrystalline gold is a promising method to achieve highly reproducible nanofilms. Cu films of more than 30 nm were deposited by the repetitive execution of underpotential deposition (UPD) of lead and a subsequent surface limited redox replacement by Cu. Both steps were carried out in the same solution. The method enables, in contrast to conventional gas phase ALD, the deposition of layers with different height on the same substrate. Deposit growth in this one-pot system was monitored in-situ with an electrochemical quartz crystal microbalance. Film thickness, measured by optical profilometry, was compared to the number of deposition cycles and indicated a highly linear dependency. Obtained layers were characterized by means of atomic force and scanning electron microscopy and showed a slight roughening with almost no increase in the effective surface area. Energy dispersive X-ray measurements confirmed the purity of deposited Cu nanofilms. It was shown, that even with a simple setup, the described method allows the reproducible deposition of Cu on polycrystalline Au.

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A. van Belkum, T. T. Bachmann, G. Lüdke, J. G. Lisby, G. Kahlmeter, A. Mohess, K. Becker, J. P. Hays, N. Woodford, K. Mitsakakis, J. Moran- Gilad, J. Vila, H. Peter, J. H. Rex, W. M. Dunne Jr., and the JPIAMR AMR-RDT Working Group
Developmental roadmap for antimicrobial susceptibility testing systems
2019 Nat Rev Microbiol, Band: 17, Seiten: 51 - 62
KurzfassungAntimicrobial susceptibility testing (AST) technologies help to accelerate the initiation of targeted antimicrobial therapy for patients with infections and could potentially extend the lifespan of current narrow-spectrum antimicrobials. Although conceptually new and rapid AST technologies have been described, including new phenotyping methods, digital imaging and genomic approaches, there is no single major, or broadly accepted, technological breakthrough that leads the field of rapid AST platform development. This might be owing to several barriers that prevent the timely development and implementation of novel and rapid AST platforms in health-care settings. In this Consensus Statement, we explore such barriers, which include the utility of new methods, the complex process of validating new technology against reference methods beyond the proof-of-concept phase, the legal and regulatory landscapes, costs, the uptake of new tools, reagent stability, optimization of target product profiles, difficulties conducting clinical trials and issues relating to quality and quality control, and present possible solutions.
S. Backe, F. Balle, B. Hannemann, S. Schmeer, U.P. Breuer
Fatigue properties of multifunctional metal‐ and carbon‐fibre‐reinforced polymers and intrinsic capabilities for damage monitoring
2019 Fatigue Fract Eng M, Nummer: 42, Seiten: 143 - 151
S Li, L Pastewka, P Gumbsch
Glass formation by severe plastic deformation of crystalline Cu|Zr nano-layers
2019 Acta Mater, Band: 165, Seiten: 577 - 586
KurzfassungWe use molecular dynamics simulation to study the formation of glasses during severe plastic deformation of crystalline Cu|Zr nano-layers in a simple shear geometry. The early stage of plasticity is governed by dislocation plasticity. Dislocation-interface interaction induces interface roughening and slow atomic-level intermixing around interfaces. A solid-state crystal-to-amorphous transition starts near the interfaces. At high strain, the interfaces are refined to merge, leading to the formation of an intermixed glassy zone that eventually spans our simulation cell. Dislocation emission is then fully suppressed and strain is fully accommodated by this glassy phase. We characterize the crystal-to-amorphous transition using local structural measures, such as the pair distribution function and Voronoi analysis. The onset of glass formation occurs at a critical shear strain that increases with layer thickness. Our simulations indicate that the parameter controlling this onset is the theoretical affine interface distance, i.e. the amorphization occurs at a critical value of around 3-4 nm that increases slightly with the increase of layer thickness. Our work provides insights on mechanically driven glass formation in multicomponent systems, as e.g. realized in ball-mills or high-pressure torsion experiments.
Margret Keuper,, S. Tang,, B. Andres,, Thomas Brox,, B. Schiele
Motion segmentation and multiple object tracking by correlation co-clustering
2019 IEEE T Pattern Anal
KurzfassungModels for computer vision are commonly defined either w.r.t. low-level concepts such as pixels that are to be grouped, or w.r.t. high-level concepts such as semantic objects that are to be detected and tracked. Combining bottom-up grouping with top-down detection and tracking, although highly desirable, is a challenging problem. We state this joint problem as a co-clustering problem that is principled and tractable by existing algorithms. We demonstrate the effectiveness of this approach by combining bottom-up motion segmentation by grouping of point trajectories with high-level multiple object tracking by clustering of bounding boxes. We show that solving the joint problem is beneficial at the low-level, in terms of the FBMS59 motion segmentation benchmark, and at the high-level, in terms of the Multiple Object Tracking benchmarks MOT15, MOT16 and the MOT17 challenge, and is state-of-the-art in some metrics.
Peter Ochs,, J. Fadili,, Thomas Brox
Non-smooth non-convex Bregman minimization: unification and new algorithms
2019 J Optimiz Theory App
KurzfassungWe propose a unifying algorithm for non-smooth non-convex optimization. The algorithm approximates the objective function by a convex model function and finds an approximate (Bregman) proximal point of the convex model. This approximate minimizer of the model function yields a descent direction, along which the next iterate is found. Complemented with an Armijo-like line search strategy, we obtain a flexible algorithm for which we prove (subsequential) convergence to a stationary point under weak assumptions on the growth of the model function error. Special instances of the algorithm with a Euclidean distance function are, for example, Gradient Descent, Forward{Backward Splitting, ProxDescent, without the common requirement of a \Lipschitz continuous gradient". In addition, we consider a broad class of Bregman distance functions (generated by Legendre functions), replacing the Euclidean distance. The algorithm has a wide range of applications including many linear and non-linear inverse problems in signal/image processing and machine learning.
Pascal Raiola, Benjamin Thiemann, Jan Burchard, Ahmed Atteya, Natalia Kapstova, Hans-Joachim Wunderlich, Bernd Becker, Matthias Sauer
On Secure Data Flow in Reconfigurable Scan Networks
2019 To appear in Conf. on Design, Automation and Test in Europe
J. Li, J. Macdonald, F. von Stetten
Review: a comprehensive summary of a decade development of the recombinase polymerase amplification
2019 Analyst, Band: 144, Seiten: 31 - 67
KurzfassungNucleic acid amplification has permeated every field in the life sciences since the introduction of the classic polymerase chain reaction (PCR) method in 1983. Yet, despite its fundamental reach, PCR has been constrained within the walls of a laboratory, due to its requirement for a sophisticated thermocycling machine, limiting external application in low-resource settings. New isothermal amplification strategies are seeking to break through traditional laboratory boundaries by providing nucleic acid replication at constant temperatures. Of these methods, recombinase polymerase amplification (RPA) is one of the fastest developing, experiencing rapid uptake and market, even though it was introduced comparatively late. Critically, RPA’s technology potentiates highly accessible and sensitive nucleic acid amplification outside of laboratory, and even self-testing. Here we provide a comprehensive review of the equipmentfree simplicity of RPA over its first decade of development. Our review includes key knowledge of RPA technology, such as its reaction components, mechanism, sensitivities and specificities, and distinctive detection methods. The review also provides know-how for developing RPA assays, and information about commercially available RPA reaction kits and accessories. We summarise critical RPA experimental tips and issues available through data mining the published literature, to assist researchers in mastering the RPA reaction. We also outline influential hotspots of RPA development, and conclude with outlooks for future development and implications for eclipsing PCR and further revolutionising the life sciences.

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Widyaya V T, Müller C, Al-Ahmad A, Lienkamp K
Three-Dimensional, Bifunctional Microstructured Polymer Hydrogels Made From Polyzwitterions and Antimicrobial Polymers
2019 Langmuir
Thorsten Falk,, Dominic Mai,, Robert Bensch,, Özgün Çiçek,, Ahmed Abdulkadir,, Yassine Marrakchi,, Anton Böhm,, J. Deubner,, Z. Jäckel,, K. Seiwald,, A. Dovzhenko,, O. Tietz,, C. Dal Bosco,, S. Walsh,, D. Saltukoglu,, T. Tay,, M. Prinz,, K. Palme,, M. Simons,, I. Diester,, Thomas Brox,, Olaf Ronneberger
U-Net – Deep Learning for Cell Counting, Detection, and Morphometry
2019 Nat Methods
KurzfassungU-Net is a generic deep-learning solution for frequently occurring quantification tasks such as cell detection and shape measurements in biomedical image data. We present an ImageJ plugin that enables non-machine-learning experts to analyze their data with U-Net on either a local computer or a remote server/cloud service. The plugin comes with pretrained models for single-cell segmentation and allows for U-Net to be adapted to new tasks on the basis of a few annotated samples.

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F. Staab, F. Balle
Ultrasonic torsion welding of ageing-resistant Al/CFRP joints: Properties, microstructure and joint formation
2019 Ultrasonics, Nummer: 93, Seiten: 139 - 144
Sturman B, Podivilov E, Werner C, Breunig I
Vectorial perturbation theory for axisymmetric whispering gallery resonators
2019 Phys Rev A, Band: 99, Seite: 013810
KurzfassungWe propose a vectorial perturbation theory for axially symmetric, generally nonspherical whispering gallery resonators made of isotropic and anisotropic optical materials. It is based on analysis of the leading terms in the coupled equations for independent light-field components, as derived from Maxwell's equations, and true boundary conditions. Strong localization of the whispering gallery modes (WGMs) near the resonator rim, controlled by the azimuth modal number m, is the main prerequisite for our analysis. The theory gives high-precision expressions for the WGM frequencies and modal functions, including the evanescent effects. One of important applications of the theory is analysis of anticrossings of the WGM resonances in anisotropic resonators detected in experiments. Simple relations for the frequency avoidance gaps during the anticrossings are derived and compared with experimental data obtained in lithium-niobate-based WGM resonators. We show also that the vectorial effects substantially restrict the field of applicability of the scalar WGM models.

2018

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Rickert J, Schuettler M, Stolle C, Wenzel F, Grigat N, Kohler F, Obert M, Rieger S, Stieglitz T, Ball T
Brain interchange: A novel brain computer interface system.
2018 Society for Neuroscience Meeting 3.-7.11.2018, San Diego, CA, USA SfN
KurzfassungTreatments of neurological disorders utilizing active implantable devices which interact with the activity of the brain are demonstrating increasingly promising advances. Next to the continuous improvement of established therapies for movement disorders, Epilepsy and chronic pain, new therapies for depression, paralysis and many more are under investigation. The current technology available for the development of these treatments is derived from the first active implants, the cardiac pacemakers, developed in mid to late 20th century: battery powered devices with few channels and limited intelligence. The Brain Interchange technology, developed in a joint effort by the University of Freiburg and CorTec, is a new system, enabling battery-free, intelligent closed-loop applications with up to 32 channels in its first version. The implantable part, including a novel hermetic encapsulation, custom electronics and firmware, were presented last year. The electrode technology will be presented in a companion poster. Here we present the progress in the development of the external parts and the software of the system and discuss potential applications. The first version of the external parts of the system manages power and communication with the implant, as well as the software for controlling the system. Physically, these parts consist of a head piece, a relay- and a controller unit. The main functions, accessible via a graphical user interface, are: managing recording and stimulation, measuring impedance and reading out humidity, temperature, supply voltage and unique ID of the implant. A filter pipeline for signal processing and feature extraction, suitable for computationally demanding closed-loop algorithms, and the control of external devices with minimal latency has also been implemented. For future collaboration partners programmable interfaces for C++, Matlab and Python are available. The development has been done under ISO-13485 and according to EN 62304. Potential applications range from closed-loop stimulation for the treatment of Parkinson’s disease or Epilepsy to the control of assistive technology in chronic paralysis or for rehabilitation purposes. Further applications could lie in closed-loop treatments in the peripheral nervous system.
Johnston M, Boehm T, Joseph K, Asplund M, Hofman U G, Thiele S, Haas C A,
Semi-automated quantification of the CNS immune response at the probe-tissue-interface.
2018 Society for Neuroscience Meeting 3.-7.11.2018, San Diego, CA, USA SfN
KurzfassungThe design of microelectrodes for electrical stimulation or recording of neuronal activity increasingly focuses on biocompatibility. Still, implantation of a cortical probe evokes a sustained sterile inflammatory response (SIR) within brain tissue. This manifests in activation of microglia, astrocytic scarring, neurodegeneration, and other molecular and morphological changes that may ultimately lead to failure of the device. To visualize the extent of the spatially limited tissue response, immunohistochemistry (IHC) is the well-established method of choice. But while qualitative assessment of resulting microscopic images can be easily accomplished, quantitative analysis poses a larger challenge to the investigator. This is partly due to the large number of images required to adequately represent the SIR, but also accounted for by high variability within and across tissue sections and animals. To this point there have been several publications that employed custom-built codes for quantification of IHC signals at the implantation sites of cortical electrodes. However, these differ greatly with respect to their evaluation methods and are not provided for open access. Hence, it is difficult to compare the extent of the SIR across different or even identical electrode types utilized by different groups. We therefore aimed at creating a semi-automated quantification method that allows fast and flexible delineation of the signal-intensity distribution from the site of lesion towards healthy brain tissue, based on the widely used software tools ImageJ and MATLAB. In this study cortical implantation of lithographically fabricated, flexible polyimide probes (10µm thickness with iridium oxide electrodes) was performed on adult Sprague Dawley rats. After different survival times transversal tissue sections were immunohistochemically stained and imaged with an epifluorescence microscope. Subsequent signal quantification was performed in concentric distance bins with flexibly adaptable size (the shape of the latter is determined by the respective cavity shape of the individual image). Processing artifacts can optionally be selected and excluded from the analysis. Apart from that normalization parameters can be modified towards the needs of the study design. This also yields the possibility of using differently processed and/or imaged tissue sections within one experimental population. Our approach provides a novel, straightforward tool for quantification of IHC-images that is versatile and adaptable for various purposes.
Johnston M, Boehm T, Joseph K, Asplund M, Hofman U G, Thiele S, Haas C A
Semi-automated quantification of the CNS immune response at the probe-tissue-interface.
2018 Society for Neuroscience Meeting 3.-7.11.2018, San Diego, CA, USA SfN
KurzfassungThe design of microelectrodes for electrical stimulation or recording of neuronal activity increasingly focuses on biocompatibility. Still, implantation of a cortical probe evokes a sustained sterile inflammatory response (SIR) within brain tissue. This manifests in activation of microglia, astrocytic scarring, neurodegeneration, and other molecular and morphological changes that may ultimately lead to failure of the device. To visualize the extent of the spatially limited tissue response, immunohistochemistry (IHC) is the well-established method of choice. But while qualitative assessment of resulting microscopic images can be easily accomplished, quantitative analysis poses a larger challenge to the investigator. This is partly due to the large number of images required to adequately represent the SIR, but also accounted for by high variability within and across tissue sections and animals. To this point there have been several publications that employed custom-built codes for quantification of IHC signals at the implantation sites of cortical electrodes. However, these differ greatly with respect to their evaluation methods and are not provided for open access. Hence, it is difficult to compare the extent of the SIR across different or even identical electrode types utilized by different groups. We therefore aimed at creating a semi-automated quantification method that allows fast and flexible delineation of the signal-intensity distribution from the site of lesion towards healthy brain tissue, based on the widely used software tools ImageJ and MATLAB. In this study cortical implantation of lithographically fabricated, flexible polyimide probes (10µm thickness with iridium oxide electrodes) was performed on adult Sprague Dawley rats. After different survival times transversal tissue sections were immunohistochemically stained and imaged with an epifluorescence microscope. Subsequent signal quantification was performed in concentric distance bins with flexibly adaptable size (the shape of the latter is determined by the respective cavity shape of the individual image). Processing artifacts can optionally be selected and excluded from the analysis. Apart from that normalization parameters can be modified towards the needs of the study design. This also yields the possibility of using differently processed and/or imaged tissue sections within one experimental population. Our approach provides a novel, straightforward tool for quantification of IHC-images that is versatile and adaptable for various purposes.
Valle G, Mazzoni A, Iberite F, D'Anna E, Strauss I, Granata G, Controzzi M, Clemente F, Rognini G, Cipriani C, Stieglitz T, Petrini FM, Rossini PM, Micera S
Biomimetic intraneural sensory encoding enhances sensation naturalness, tactile sensitivity and manual dexterity in a bidirectional prosthesis.
2018 Society for Neuroscience Meeting 3.-7.11.2018, San Diego, CA, USA SfN
KurzfassungThe lack of sensory feedback during grasping is a very important limitation of current hand prostheses, which affects their everyday usability. In the last years several research groups have demonstrated that nerve stimulation by implantable peripheral nerve interfaces can be reliably used to restore sensory feedback to upper limb amputees. They have shown that direct neural stimulation of peripheral nerves can effectively provide tactile information to the amputees, controlling the sensation intensity by modulating either the amplitude or the frequency of the injected stimuli. However, efforts are still necessary to identify encoding strategies converting tactile information into neural stimulation patterns capable of eliciting percepts that are both felt as natural and effective for prosthesis control. In this study, we compared the naturalness and efficacy of a set of encoding strategies based on biomimetic (model-driven) frequency modulation, amplitude modulation, or combinations of both. Such strategies were used to deliver neural stimulation to a trans-radial amputee implanted with intraneural electrodes (TIMEs). Frequency modulation was based on a biomimetic model (TouchSim) able to reproduce nerve activation patterns of the multifaceted mechanics of the skin and mechano-transduction. It was perceived as more natural, while amplitude modulation enabled better performance in tasks requiring fine identification of the applied force. Notably, hybrid encoding strategies involving both amplitude and frequency modulation were able to convey at least as much information as the amplitude modulation (for the completion of tasks), and were perceived at least as natural as the frequency modulation. The hybrid strategies improved the gross manual dexterity of the subjects during functional tasks while maintaining high manual accuracy. They also improved the level of prosthesis embodiment and reduced abnormal body perceptions of the phantom limb (“telescoping”). Encoding strategies based on the combination of biomimetic frequency modulation and amplitude modulation are able to provide highly sensitive and natural percepts and should be preferred in bidirectional prosthesis use.
Bast H, Brosi P, Storandt S
Efficient Generation of Geographically Accurate Transit Maps
2018 SIGSPATIAL
KurzfassungWe present LOOM (Line-Ordering Optimized Maps), a fully automatic generator of geographically accurate transit maps. The input to LOOM is data about the lines of a given transit network, namely for each line, the sequence of stations it serves and the geographical course the vehicles of this line take. We parse this data from GTFS, the prevailing standard for public transit data. LOOM proceeds in three stages: (1) construct a so-called line graph, where edges correspond to segments of the network with the same set of lines following the same course; (2) construct an ILP that yields a line ordering for each edge which minimizes the total number of line crossings and line separations; (3) based on the line graph and the ILP solution, draw the map. As a naive ILP formulation is too demanding, we derive a new custom-tailored formulation which requires significantly fewer constraints. Furthermore, we present engineering techniques which use structural properties of the line graph to further reduce the ILP size. For the subway network of New York, we can reduce the number of constraints from 229,000 in the naive ILP formulation to about 3,700 with our techniques, enabling solution times of less than a second. Since our maps respect the geography of the transit network, they can be used for tiles and overlays in typical map services. Previous research work either did not take the geographical course of the lines into account, or was concerned with schematic maps without optimizing line crossings or line separations.
Stieglitz T, Vomero M, Joseph K, Johnston M, Ciarpella F, Kirsch M, Boehm T, Fagida L, Thiele S, Haas C A, Hofmann U G, Asplund M
How flexibility and probe size influence chronic reliability: A study on batch processed polyimide-based intracortical neural arrays.
2018 Society for Neuroscience Meeting 3.-7.11.2018, San Diego, CA, USA SfN
KurzfassungFor short and long term neural applications, it is desirable to reduce or ideally eliminate the foreign body response to the implanted devices. One way to do so is to minimize the size of the device and thus the bending stiffness of the implant affecting the soft brain tissue. Recent findings in the field of neural engineering have led to the development of ultra-thin and ultra-flexible intracortical electrode arrays, presumably “invisible” for the host tissue and unable to trigger a noticeable immune response in long-term applications. However, reduced probe size comes at the cost of fewer individual electrodes, more challenging handling and fabrication, as well as mechanical properties less suited for chronic in vivo experiments. It is therefore important to better understand which design parameters offer the best trade-off. In this study, we compare two kinds of polyimide-based electrode arrays which differ only in their width: one kind is only 30 µm wide while the other has a width of 100 µm. Both device types are 12 µm thick and display electrodes 20 µm in diameter, spaced so that they target each one of the six cortical layers. The devices were chronically implanted into the brain of adult rat models and different time points were selected for perfusion and subsequent evaluation and quantification of the differences in the elicited immune response of the brain (via immunohistochemistry). Some of the probes were also used for long term recording of electrophysiological activity. Control devices (i.e. identical but without connector) were used to study the influence of the connector and cement on the short and long term tissue reaction to the implants. The wider probes (100 µm width) featured a pair of identical electrodes per cortical layer (instead of a single one) with the aim to achieve a better reconstruction of the neuronal configuration and status around the probe. The study’s goal is to systematically investigate the influence of selected geometrical parameters on the performance of thin-film polyimide based neural prostheses in vivo. Key concept: This study is part of a bigger project which aims to find a clear answer to the question “how small does a neural probe have to be to become invisible for the host tissue and yet to record long term high quality signals?”
Badi M, Wurth S, Kaeser M, Cvancara P, Stieglitz T, Courtine G, Capogrosso M, Bloch J, Rouiller E, Micera S
Neuroanatomical, computational, and experimental evidences for the use of intraneural peripheral nerve stimulation to induce fine hand movements.
2018 Society for Neuroscience Meeting 3.-7.11.2018, San Diego, CA, USA SfN
KurzfassungCervical spinal cord injury (SCI) and stroke severely impact grasping movements required for activities of daily living. Intraneural peripheral nerve stimulation enables specific activation of passing fibers. This paradigm has restored precise leg movements in animal models of SCI and selective sensation in human amputees. Intraneural peripheral nerve stimulation may also restore fine grasping in paralyzed hands, but this possibility has not been investigated. Here, we assess the feasibility of using intrafascicular electrical stimulation of peripheral nerves to produce precise hand movements in the non-human primate (NHP). We first extensively characterized the branching points of the median, radial, and ulnar nerves to their target muscles in the adult macaca fascicularis in order to identify the optimal implantation site for intraneural electrodes. We then reconstructed the tridimensional structure of the identified portion of each nerve in order to analyze the fascicular organization within the nerve at this level. Additionally, we assessed the distribution of motor fibers within the fascicles using immunohistochemistry. The obtained data was used to build realistic computational models of intraneural peripheral nerve stimulation for each nerve. The simulations confirmed the advantages of using intrafascicular electrodes to induce precise hand movements, demonstrating the possibility to selectively recruit patches of motor fibers without a priori knowledge of the electrode placement. We validated these results during electrophysiology experiments using transverse intrafascicular multichannel electrodes (TIMEs) implanted in the nerves of anesthetized NHPs. The stimulation achieved a selective recruitment of wrist and finger flexors and extensors in a reproducible manner across animals. We exploited these results to determine stimulation sequences that aimed at reproducing the muscle activation patterns underlying different grasping movements. For this, we mapped the obtained muscle recruitment maps to continuous EMG recordings during behavioral experiments and automatically optimized the selection of stimulation channels for each phase of the movement such as to reproduce the desired EMG pattern. Taken together, these results suggest encouraging evidences for the usability of the TIMEs to restore fine hand control after paralysis.
Gkogkidis CA, Bentler C, Wang X, Scheiwe C, Cristina Schmitz H, Stieglitz T, Ball T
Neurophysiological recording and stimulation using an off-the-shelf component wireless brain implant.
2018 Society for Neuroscience Meeting 3.-7.11.2018, San Diego, CA, USA SfN
KurzfassungBrain implants are increasingly used in neuroscientific research and medical applications. The requirements for such implants are diverse due to different experimental paradigms, scientific problem to address and demands by the researcher or clinician. To overcome these requirements, brain implants that can be built in a customized fashion might be beneficial. We previously introduced such a research grade wireless brain implant, developed exclusively using off-the-shelf components, which allows for quick and customized assembly. To verify the operability of the device during recording and stimulation, we present neurophysiological data obtained in an ovine animal model. During general anesthesia, the 63-channel µECoG electrode array was placed on the cortex of the sheep brain and both auditory and electrical stimuli were used to evoke neurophysiological responses which were recorded at a sampling rate of 4 kHz. Experiments performed in this study were conducted according to EU Directive 2010/63/EU and approved by the Animal Committee of the University of Freiburg and the Regierungspraesidium Freiburg, Germany. We show that our off-the-shelf research grade brain implant is capable to reliably record neurophysiological brain activity and electrically stimulate, evoking cortico-cortical responses, under in vivo conditions. The obtained neurophysiological activity showed clear responses with distinct spatio-temporal patterns to both auditory stimuli and cortical electrical stimulation, the latter with response patterns systematically depending on the exact stimulation site. In addition, spectral analysis revealed a neurophysiological frequency profile of the recorded activity which is in agreement with the well-known frequency power-law, i.e., the frequency-dependent linear decrease of log-log absolute spectral power. The presented neurophysiological data are in agreement with previously published recording and stimulation results obtained in sheep using different implantable devices that were not off-the-shelf. The results and their neurobiological implications as presented here highlight that off-the-shelf component brain interfacing devices are feasible and thus open up new avenues for implant-based research, especially when flexible requirements have to be addressed, as it is often the case in basic neuroscientific research. In the future we want to expand our approach to higher channel counts (128-channel high-resolution µECoG electrode arrays), higher recording sampling rate, and functional systems beyond the auditory system, as further use cases of our implant concept in neurotechnological research.
Petrini FM, Valle G, Bumbasirevic M, Barberi F, Guiraud D, Stieglitz T, Micera S, Raspopovic S
Sciatic intraneural stimulation evokes selective sensations from the phantom leg of trans-femoral amputees.
2018 Society for Neuroscience Meeting 3.-7.11.2018, San Diego, CA, USA SfN
KurzfassungLeg amputation destroys the communication between brain and environment during walking. Leg amputees rely on practically inexistent and often uncomfortable haptic feedback from the stump-socket interaction to monitor ground and obstacles contact, climb stairs, or walk in challenging environments. The lack of sensory feedback causes specific impairments to subjects that do not perceive the prosthesis as part of their body and risk falls, have decreased mobility, increased cognitive burden during walking resulting in prosthesis abandonment. In hand amputees, to restore the bidirectional communication, nerve interfaces have directly linked sensors readout from robotic hands to direct stimulation of nerves above injury. We believe that this strategy could also restore sensations from missing legs, with many scientific and technological barriers to overcome. It has never been proved that the electrical stimulation of the leg nerves by implantable neural interfaces can induce reliable sensations from missing leg and foot. In this work we developed a leg prosthesis restoring sensory feedback by means of direct nerve stimulation injected through transversal intraneural electrodes (TIME) implanted in the sciatic nerve. The stimulation was driven by the readout of pressure sensors placed under the prosthetic foot, and an encoder embedded in the prosthetic knee. We assessed the capability of 3 transfemoral amputees to recognize, blindfolded and acoustically insulated, the location where the prosthetic foot was touched and the degree of flexion of the prosthetic knee. The subjects were asked to recognize only touch, only flexion and then both conditions at the same time. We compared the performance when sensory feedback was restored and when no nerve stimulation was delivered. We found that single and double condition-tasks were executed on average respectively with a success rate of about 85% and 75%, when sensory feedback was provided. Without nerve stimulation the average success rate dropped to 25%.
Bast H, Brosi P
Sparse Map-Matching in Public Transit Networks with Turn Restrictions
2018 SIGSPATIAL
KurzfassungWe investigate the following map-matching problem: given a sequence of stations taken by a public transit vehicle and given the underlying network, find the most likely geographical course taken by that vehicle.We provide a newalgorithm and tool, which is based on a hidden Markov model and takes characteristics of transit networks into account. Our tool can be useful for the visualization of transit lines in map services, for transit data providers, and for an on-line matching of live passenger GPS data to a public transit vehicle. We evaluate our tool on real-world data, and compare it against two baselines. The shapes produced by our tool are very close to the true shapes. We have made our software publicly available,enabling full reproducibility of our results.
Johnston M, Böhm T, Joseph K, Asplund M, Hofmann UG, Thiele S, Stieglitz T, Haas CA
QUANTIFY – a semi-automated quantification of the CNS immune response at the probe-tissue-interface.
2018 Society for Neuroscience Meeting, Nov. 3rd-7th, 2018, San Diego, Ca, USA
Pfau J, Ganatra D, Weltin A, Urban G, Kieninger J, Stieglitz T
Electrochemical Stability of Thin-Film Platinum as Suitable Material for Neural Stimulation Electrodes.
2018 52nd Annual Conference of the German Society for Biomedical Engineering, DGBMT“ , Aachen, 26.09-28.09.18
Pasluosta C, Kiele P, Stieglitz T
Eliciting somatosensory percepts via multi-channel wireless electrical stimulation of afferent nerves .
2018 2018 52nd Annual Conference of the German Society for Biomedical >Engineering, DGBMT" , Aachen, 26.09-28.09.18
Matthias Althoff, Stanley Bak, Xin Chen, Chuchu Fan, Marcelo Forets, Goran Frehse, Niklas Kochdumper, Yangge Li, Sayan Mitra, Rajarshi Ray, Christian Schilling, Stefan Schupp
ARCH-COMP18 Category Report: Continuous and Hybrid Systems with Linear Continuous Dynamics
2018
Kondov I, Faubert P, Müller C
Virtual design of nickel-based electrocatalysts for the oxygen reduction reaction
2018 E-MRS European Materials Research Society Warschau
Ledford, Noah, Paul, Hanna, Isakov, Matti, Hiermaier, Stefan
High rate loading of hybrid joints in a Split Hopkinson Tension Bar
2018 International Conference on the Mechanical and Physical Behaviour of Materials under Dynamic Loading (DYMAT)/Arcachon EPJ Web of Conferences, Band: 183
KurzfassungBonded joints are nowadays seen as one of the preferred joining methods in aerospace applications. However, the difficulty in certifying bond strength and the relatively low energy absorption capability of the joint are barriers to widespread adoption. The use of a hybrid joint, that is, the combination of a mechanical and a bonded joint, allows for a fail-safe design and offers improved performance of the joint. The quasi-static properties of hybrid joints have been investigated by a number of researchers. In contrast, the high rate loading regime has been only sparsely investigated. In this work, hybrid joints are tested in quasi-static and high rate loading in order to analyze their loading rate dependence. The hybrid joint studied is a composite-aluminum double lap shear joint with Sikaforce 7752 adhesive and Hi-Lite-315 countersunk titanium bolts. In order to quantitatively analyze the high rate behavior of the hybrid joints and their respective sub-components, additional tests are carried out on simply bonded and simply bolted specimens. The high rate characterization was performed with a Split Hopkinson Tension Bar. The main challenges for these tests are the relatively large specimen size and complex specimen geometry needed to properly characterize the joint behavior, which both are in contradiction with the assumptions of the classical Split Hopkinson Bar-analysis. In this paper we describe an approach to solve these challenges based on an elastic wave analysis of the system.
Bast H, Schnelle N
Efficient and Convenient SPARQL+Text Search: A Quick Survey
2018 Reasoning Web International Summer School 2018 Springer, Cham, Seiten: 26 - 34
KurzfassungThis is a quick survey about efficient search on a text corpus combined with a knowledge base. We provide a high-level description of two systems for searching such data efficiently. The first and older system, Broccoli, provides a very convenient UI that can be used without expert knowledge of the underlying data. The price is a limited query language. The second and newer system, QLever, provides an efficient query engine for SPARQL+Text, an extension of SPARQL to text search. As an outlook, we discuss the question of how to provide a system with the power of QLever and the convenience of Broccoli. Both Broccoli and QLever are also useful when only searching a knowledge base (without additional text).
Pasluosta C, Kiele P, Stieglitz T
Toward a Multi-Channel Wireless System for Electrical Stimulation of Peripheral Nerves: Modelling and Simulation of Signal Transmission.
2018 22nd Annual Conference of the International Functional Electrical Stimulation Society, IFESS" , Nottwil, 28.08-31.08.18
Alt MT, Mittnacht A, Stieglitz T
Implantable Glass Waveguides and Coating Materials for Chronic Optical Medical Applications.
2018 40th International Conference of the IEEE Engineering in Medicine and Biology Society, 17.-21.07.2018, Oahu, Hawaii, USA IEEE, Seiten: 4595 - 4598
KurzfassungAn innovative fabrication process of glass waveguides on silicon substrates for miniaturized implants is presented. Thin glass was bonded on oxidized silicon wafers and patterned using wet etching. Multimode waveguides with different shapes and a low surface roughness as well as low scattering of light were successfully fabricated. For efficient coupling of light and accurate alignment, KOH-grooves were etched in the silicon with respect to the glass waveguides to attach optical fibers from external light sources. Towards higher biostability, several coating and cladding materials were evaluated in accelerated in vitro tests in 60°C PBS. TiO2, SiC polyimide, Parylene C and SU-8 showed a very stable optical transmittance after 320 days in accelerated aging while PECVD Si3N4 showed significant changes within the first days.
Kahn S, Scholz D, Ordonez JS, Stieglitz T
PDMS Gasket Underfill for Long-Term Insulation of High Density Interconnects in Active Implantable Medical Devices
2018 40th International Conference of the IEEE Engineering in Medicine and Biology Society, 17.-21.07.2018, Oahu, Hawaii, USA , Seiten: 2941 - 2944
KurzfassungThis work presents reliability investigations of silicone gasket as solid underfill for interconnection interfaces in hybrid implant systems with high channel count flexible electrode arrays and hermetically packed electronics. The gasket is fabricated by laser structuring thin sheet of silicone rubber. The surface activation of silicone sheet ensures mechanical bonds with the mating surfaces thereby improving the mechanical stability of the assembly and the insulation of the interconnects. The gasket samples with 10 × 10 openings for interconnect pads, each with diameter of 270 μm and a center to center pitch size of 490 μm, were sandwiched between a polyimide array and a metallized ceramic substrate. The gasket maintained high insulation impedance of 15 ± 0.30 MΩ between the adjacent interconnects with markedly capacitive behavior (phase angle, -89 °) after 17 weeks in soaked conditions under accelerated aging at 60 °C. The gasket also survived electrical stresses and sustained high impedance (10.93 MΩ with phase angle of -88 °) when subjected to constant 3 VDC for 100 days.
Pascal Raiola, Michael A. Kochte, Ahmed Atteya, Laura Rodríguez Gómez, Hans-Joachim Wunderlich, Bernd Becker, Matthias Sauer
Detecting and Resolving Security Violations in Reconfigurable Scan Networks
2018 IEEE International Symposium on On-Line Testing and Robust System Design
Banerjee K, Rajaeipour P, Ataman C, Zappe H
A highly-miniaturized optofluidic refractive adaptive optics system
2018 Imaging and Applied Optics 2018, Orlando, Florida, USA Imaging and Applied Optics, OSA Publishing
Erhardt JB, Martinez JA, Cork TE, Gessner I, Mathur S, Stieglitz T, Ennis DB
Assessment of Iron Oxide Nanoparticle Concentration for Distinct Intercranial EEG Electrode Localization in MRI.
2018 Proceedings of the 26th scientific meeting, International Society for Magnetic Resonance in Medicine, Paris, France , Seiten: 4057 - 4057
KurzfassungIntercranial EEG (icEEG) electrodes are implanted for pre-surgical assessment of cortical electrical activity in patients with epilepsy. MRI helps to localize the implant with respect to the individual’s anatomy and fMRI can improve understanding of the neuropathology. However, the magnetic susceptibility artifacts caused by the metal components of commercially available implants produce MRI artifacts that compromise the results especially in the direct vicinity of the implants. Next generation “thin-film” implants which feature 100x less metal thickness can mitigate these artifacts, but thin-film implants produce inconspicuous MRI signal voids in many clinical MRI sequences. Imperatively, physicians need to know the implant position and the value of EEG increases with the precision of electrode localization. Therefore, we investigated various concentrations of super paramagnetic iron oxide (SPIO) nanoparticles (NP) to label thin-film implants for localization in MRI using a range of sequences. In particular, we aim to create a marker that conspicuously renders the implant, enables spatial localization of the individual electrodes, and keeps disruptive imaging artifacts small.
Stieglitz T
Stability of materials and flexible neural probes for recording, electrical and optical stimulation.
2018 Colloquium des SFB 889 "Cellular Mechanisms of Sensory Processing", Universitätsmedizin Göttingen, 19.06.2018, Göttingen
Weidlich A, Künzel T, Klumpp F
Bidding Strategies for Flexible and Inflexible Generation in a Power Market Simulation Model
2018 1st International Workshop on Energy Market Engineering ACM e-Energy 2018, Band: 1, Nummer: 1, Seiten: 532 - 537
KurzfassungThis paper presents an electricity market simulation model that focuses on the distinction between flexible and inflexible generation, and formulates bidding strategies for capacities of either type. Bid formulation for flexible power plants, storage and demand response units at a balancing power market and an energy exchange market are described, and exemplary results from the simulation model are presented. It is shown that the simulation model can realistically reproduce market outcomes for the example of the German market zone, and that it can also simulate negative market prices. Results reveal that power plants could be deployed in a more flexible manner than they are currently done in actual market operation, where larger variations of output are avoided especially for nuclear and lignite-fired power plants. The model can be used for analyzing future energy scenarios of high shares of variable renewable energy (VRE), and help answering research questions related to the required system flexibility for balancing out VRE fluctuations.
Stieglitz T, Cvancara P, Mueller M, Eickenscheidt M, Liljemalm R, Fiedler E, Kahn S
Implantable microelectrodes - opportunites and challenges with respect to selectivity, stability and reliabilty.
2018 World Congress on Medical Physics and Biomedical Engineering (IUPESM 2018), June 3-8, 2018, Prague, Tschechien
KurzfassungMiniaturized electrode arrays for electrical stimulation in neural implants have to be stable, functional and reliable over the life-time of the implant, which is at best at least as long as the life time of the recipient. While cardiac pacemaker and cochlear implant electrodes stay stable for long time due to well established materials and precision mechanics manufacturing, more complex implants with higher channel count and integration density requires different technologies as well as materials. It is not only the dimension of thin-film metals that is more demanding than the one of solid electrode sheets in cochlear implants, cardiac, spinal cord and brain pacemakers but also the fact that surface effects predominate and promote corrosion mechanisms that are hardly seen in the established applications. In addition, adhesion of metals and polymer insulation is of utmost importance for device longevity and reliability. How can these challenges be combined with the target specifications for high spatial selectivity and the possibility of current steering when using multipolar stimulation paradigms ? This presentation combines material sciences foundations with requirements of electrical stimulation in movement rehabilitation to discuss opportunites and challenges in development of miniaturized electrode arrays. Examples include delivery of sensory feedback via stimulation of afferent fibers in the peripheral nervous system and recording of neural signals from the central nervous system as input parameter in brain-computer-interface applications to control movement of either artificial or paralyzed limbs. Results from preclinical as well as from human clinical trials are presented to discuss material-tissue interactions and microsystem stability in chronic implantation scenarios and the influence of these findings to spatial selectivity that is needed for sophisticated movement rehabilitation by functional electrical stimulation.
Watson, Erkai, Maas, Hans-Gerd, Schaefer, Frank, Hiermaier, Stefan
Trajectory based 3D fragment tracking in hypervelocity impact experiments
2018 Symposium "Towards Photogrammetry 2020"/Riva del Garda ISPRS, 2018 (The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLII-2, Band: XLII-2
KurzfassungCollisions between space debris and satellites in Earth’s orbits are not only catastrophic to the satellite, but also create thousands of newfragments, exacerbating the space debris problem. One challenge in understanding the space debris environment is the lack of data onfragmentation and breakup caused by hypervelocity impacts. In this paper, we present an experimental measurement technique capableof recording 3D position and velocity data of fragments produced by hypervelocity impact experiments in the lab. The experimentalsetup uses stereo high-speed cameras to record debris fragments generated by a hypervelocity impact. Fragments are identified andtracked by searching along trajectory lines and outliers are filtered in 4D space (3D + time) with RANSAC. The method is demonstratedon a hypervelocity impact experiment at 3.2 km/s and fragment velocities and positions are measured. The results demonstrate thatthe method is very robust in its ability to identify and track fragments from the low resolution and noisy images typical of high-speedrecording.
Stieglitz T
Introduction to Optogenetics.
2018 Fachgruppe Intelligente Implantate, microTEC Südwest, 16.05.2018, Rottweil (2018)
Ruther P
LED-based MEMS Tools for Optogenetic Applications Aside from Cerebral Tissue
2018 ICAN – International Conference for Advanced Neurotechnology, University of Michigan, Ann Arbor, USA, 7./8. May 2018
Stieglitz T
Stability and Functionality of Thin-film Recording and Stimulation Electrodes in the Peripheral and Central Nervous System.
2018 International Conference on Advanced Neurotechnologies (ICAN), May 6-8, 2018, Ann Arbor, MI, USA
Klein E, Gossler C, Paul O, Ruther P
Thin-film LED Arrays on Flexible Substrates With Improved Thermomechanical Behaviour
2018 ICAN – International Conference for Advanced Neurotechnology, University of Michigan, Ann Arbor, USA, 7./8. May 2018
Ahmed Atteya, Michael Kochte, Matthias Sauer, Pascal Raiola, Bernd Becker, Hans-Joachim Wunderlich
Online Prevention of Security Violations in Reconfigurable Scan Networks
2018 IEEE European Test Symposium
Johanna Sepulveda, Damian Aboul-Hassan, Georg Sigl, Bernd Becker, Matthias Sauer
Towards the Formal Verification of Security Properties of a Network-on-Chip Router
2018 IEEE European Test Symposium
Felix Neubauer, Jan Burchard, Pascal Raiola, Jochen Rivoir, Bernd Becker, Matthias Sauer
Efficient Generation of Parametric Test Conditions for AMS Chips with an Interval Constraint Solver
2018 IEEE VLSI Test Symposium (VTS'18)
KurzfassungThe characterization of analog-mixed signal (AMS) silicon requires a suitable pattern set able to exercise the parametric operational space to - among other tasks - validate the correct (specified) working behaviour of the device under test. As experience shows, most of the unexpected problems occur for very specific value combinations of a few test condition variables that were not expected to have an influence. Additionally, restrictions on the operational conditions have to be taken into account. We present a method to efficiently create a set of test conditions to cover such a constrained search space with a user-defined density. First, an initial test condition set is generated using quasirandom Sobol sequences. Secondly, we analyse the test conditions to identify and fill uncovered areas in the parameter space using the in-house interval constraint solver iSAT3. The applicability of the method is demonstrated by experimental results on a 19-dimensional search space using a realistic set of constraints.
Stevens L, Hauser H, Höhn O, Tucher T, Wellens C, Jahn R, Glaubitt W, Müller C, Bläsi B
Nanoimprinted sol-gel- materials as antireflective structures for silicon solar cells
2018 SPIE Konferenz Straßburg 2018 SPIE Konferenz Straßburg
S. Vierrath, M. Breitwieser, C. Klose, M. Klingele, S. Thiele
Novel approaches to tailor the PEM|electrode interface for fuel cells with increased power density
2018 innBW Wissenschaftlertreffen Stuttgart, 21.04.2018
F. Staab, F. Balle
Ultraschalltorsionsschweißen von alterungsbeständigen Al/CFK-Verbunden – Konzepte, Prozess und Eigenschaften
2018 3. Hybrid Materials and Structures, Bremen
Stieglitz T
Bioelektronische Medizin-Versprechen und Herausforderungen.
2018 microTEC Südwest Clusterkonzerenz 2018, 16.-17.04.2018, Konzerthaus Freiburg
Stieglitz T
Neurostimulation zur Wiederherstellung sensorischen Feedbacks.
2018 MedTech Summit, 11.-12.04.2018, Messe Nürnberg
Linus Feiten, Karsten Scheibler, Bernd Becker, Matthias Sauer
Using different LUT paths to increase area efficiency of RO-PUFs on Altera FPGAs
2018 TRUDEVICE Workshop, Dresden
KurzfassungDelay-based PUFs are well suited to be implemented on FPGA chips. A delay line is commonly achieved by routing the signal through a number of adjacent lookup tables (LUTs). This however uses only one of all possible routings per LUT. We suggest to implement RO-PUFs using all possible routings that can be configured at runtime, which allows to gather much more device-specific information per chip area. Furthermore, the number of PUF response bits can be increased even further without extra hardware or software if a certain degree of correlations among the response bits is accepted. The degree of correlations is proportional to the growth of response bits, so a design decision can be made. To make this decision, a metric to quantify the degree of correlations is needed, which has so far been mostly neglected in the analyses of PUF implementations.
Stieglitz T
When technology hits the nerve-intelligent implants in neurological treatment and rehabilitation.
2018 XPOMET, Die Convention für Innovation und Hightech in der Medizin, 21.-23.03.2018, Leipzig
Dominik Jan Schott, Muhammad Faisal, Fabian Höflinger, Leonhard M Reindl
A Multichannel Acoustic Chirp-Spread Modulation Approach Towards Diver-to-Diver Communication
2018 Hammamet, Tunesien 2018 15th International Multi-Conference on Systems, Signals & Devices (SSD), IEEE, Seiten: 475 - 479
KurzfassungIn this work, we propose a single and multiband chirp signals for communication in the air and underwater channel. A Raspberry Pi based transceiver system and MATLAB are used for the demodulation of the chirp signals. The experiments, for both air and water, are conducted in static conditions, that is the transmitter and receiver are fixed. To increase the efficiency of signal processing, down-conversion or bandpass sampling is implemented on the receiver side. We use transmission bands between 60~kHz and 70kHz to reduce the impact of divers' communication on the maritime ecosystem and its natural communication bands. The structure of the demodulation is discussed in detail with focus on the frame detection and decision algorithm. In several different settings, we demonstrate the performance of this approach and transmit data of up to 12 Byte with data rates of 100 and 200 bit/s over 0.25 m in air and 4.5 m in water inside a highly echoic environment.

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Hoschke, Klaus, Pfaff, Aron, Fleig, Luisa, Bierdel, Marius, Jaecklein, Martin, Riedel, Werner, Hiermaier, Stefan
A parametric mesostructural approach for robust design of additive manufacturing parts
2018 Fraunhofer Direct Digital Manufacturing Conference (DDMC)/Berlin Fraunhofer Direct Digital Manufacturing Conference DDMC 2018, Band: 1
KurzfassungAdditive Manufacturing (AM) allows for production of potentially complex design solutions and motivates the use of Structural Optimization tools in product development to chase the structural limit of a design problem and its solution concept. Scratching on the limits of the material strength, design solutions can lack robustness concerning simplifications in model assumptions and uncertainties. However, the design freedom with AM can also actively be used to enhance robustness and reliability of solutions. To this end, an approach is presented that introduces Parametric Mesostructures into selective areas of the Additive Design. Structural members and coherent mechanical characteristics of these mesostructures can significantly reduce local stress peaks and can account for uncertainties, e.g. direction of load application. Their design is motivated by Structural Optimization and analysis results. Implementation of the approach is demonstrated and discussed on the example of a structural aircraft component.
Felix Neubauer, Jan Burchard, Pascal Raiola, Jochen Rivoir, Bernd Becker, Matthias Sauer
High-Coverage AMS Test Space Optimization by Efficient Parametric Test Condition Generation
2018 GI/ITG Workshop “Testmethoden und Zuverlässigkeit von Schaltungen und Systemen”
Ruther P
Interfacing the brain with micromachined implants
2018 TU Einhoven
Uwe Wagschal, Thomas Metz, Thomas Waldvogel, Bernd Becker, Linus Feiten, Samuel Weishaupt
Online real-time-response measurement in real life settings: the Debat-O-Meter
2018 Cologne 20th General Online Research Conference (GOR)
KurzfassungPolitical debates have attracted substantial public and academic attention due to their prominent role in election campaigns. Reaching a tremendous number of potential voters, TV debates concentrate the electoral contest into a one-evening format that covers all major topics and main contenders. As "miniature campaigns" they reach many undecided and serve as (often the only) source of direct campaign information for voters less sophisticated or attentive to politics. In recent years Real Time Response Measurement gained international importance in political communication research.
F. Staab, F. Balle
Prozessuntersuchungen zum Ultraschallschweißen von alterungsbeständigen Al/CFK-Übergangsstrukturen
2018 DGM-Fachausschuss „Hybride Werkstoffe und Strukturen", Dortmund
Stieglitz T
“Wenn Technik den Nerv trifft… Miniaturisierte Implantate in der Neurotechnik und für Elektrozeutika”
2018 Fachtagung Kunststoff trifft Medizintechnik, 31.01.-01.02.2018, Leipzig (2018).
Stieglitz T
Bioelektronische Medizin‑Versprechen und Herausforderungen
2018 Hochrhein-Seminar, Technisches Gymnasium Waldshut
Pawel Gawrychowski, Fabian Kuhn, Jakub Lopuszanski, Konstantinos Panagiotou, Pascal Su
Labeling Schemes for Nearest Common Ancestors through Minor-Universal Trees
2018 29th ACM-SIAM Symposium on Discrete Algorithms (SODA) , Seiten: 2604 - 2619
Bast H, Azar Y, Herman G
26st European Symposium on Algorithms - LIPIcs
, Band: 112, 2018
B. Shanahan, B. Britton, S. Holdcroft, R. Zengerle, S. Thiele, M. Breitwieser
30 μm thin, highly conductive PBI-based anion exchange membrane (AEM) for VRFB applications
2018 IFBF - The International Flow Battery Forum, Lausanne/Schweiz, 10. – 12.07.2018
Christian Zimmermann,, T. Welschehold,, C. Dornhege,, W. Burgard,, Thomas Brox
3D Human Pose Estimation in RGBD Images for Robotic Task Learning
2018

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Marx M, Rombach S, Nessler S, De Dorigo D, Manoli Y
A 141μW High Voltage MEMS Gyroscope Drive Interface Circuit based on Flying Capacitors
2018 IEEE Journal Solid-State Circuits (JSSC), early access
Butz N, Taschwer A, Nessler S, Manoli Y, Kuhl M
A 22V Compliant 56µW Twin-Track Active Charge Balancing Enabling 100% Charge Compensation Even in Monophasic and 36% Amplitude Correction in Biphasic Neural Stimulators
2018 IEEE Journal Solid-State Circuits (JSSC), Band: 53, Nummer: 8, Seiten: 2298 - 2310
Marx M, De Dorigo D, Nessler S, Rombach S, Manoli Y
A 27μW 0.06mm² Background Resonance Frequency Tuning Circuit Based on Noise Observation for a 1.71 mW CT-ΔΣ MEMS Gyroscope Readout System With 0.9°/h Bias Instability
2018 IEEE Journal Solid-State Circuits (JSSC), Band: 53, Nummer: 1, Seiten: 174 - 186
Khatri B, Lappe K, Nötzel D, Pursche K, Hanemann T
A 3D-Printable Polymer-Metal Soft-Magnetic Functional Composite-Development and Characterization
2018 Materials, Band: 11, Seiten: 189-1 - 189-12
KurzfassungIn this work, a 3D printed polymer–metal soft-magnetic composite was developed and characterized for its material, structural, and functional properties. The material comprises acrylonitrile butadiene styrene (ABS) as the polymer matrix, with up to 40 vol. % stainless steel micropowder as the filler. The composites were rheologically analyzed and 3D printed into tensile and flexural test specimens using a commercial desktop 3D printer. Mechanical characterization revealed a linearly decreasing trend of the ultimate tensile strength (UTS) and a sharp decrease in Young’s modulus with increasing filler content. Four-point bending analysis showed a decrease of up to 70% in the flexural strength of the composite and up to a two-factor increase in the secant modulus of elasticity. Magnetic hysteresis characterization revealed retentivities of up to 15.6mT and coercive forces of up to 4.31 kA/m at an applied magnetic field of 485 kA/m. The composite shows promise as a material for the additive manufacturing of passive magnetic sensors and/or actuators.
Shui B, Keller M, Kuhl M, Manoli Y
A 70.1dB 0.0045mm² Low-Power Continuous-Time Incremental Delta-Sigma Modulator for Multi-Site Neural Recording Interfaces
2018 Proceedings of the IEEE International Symposium on Circuits and Systems (ISCAS)
Taschwer A, Butz N, Koehler M, Rossbach D, Manoli Y
A Charge Balanced Neural Stimulator with 3.3V to 49V Supply Compliance and Arbitrary Programmable Current Pulse Shapes
2018 Proceedings of the IEEE Biomedical Circuits and Systems Conference (BioCAS)
De Dorigo D, Moranz C, Graf H, Marx M, Shui B, Kuhl M, Manoli Y
A Fully Immersible Deep-Brain Neural Probe with Modular Architecture and a Delta-Sigma ADC Integrated Under Each Electrode for Parallel Readout of 144 Recording Sites
2018 IEEE International Solid-State Circuits Conference (ISSCC), Digest of Technical Papers, Seiten: 462 - 464
Amayreh M, Baaken G, Behrends J, Manoli Y
A Fully Integrated Current-Mode Continuous-Time Delta-Sigma Modulator For Biological Nanopore Read-Out
2018 IEEE Transactions on Biomedical Circuits and Systems ( TBCAS), early access
Hoch K, Pothof F, Becker F, Paul O, Ruther P
A Magnetic, Micro-spring-suspended System for the Safe Electrical Interconnection of Neural Implants
2018 IEEE MEMS Conf. 2018, Belfast, Ireland , Seiten: 369 - 372
Cai Y, Manoli Y
A Piezoelectric Energy-Harvesting Interface Circuit with Fully Autonomous Conjugate Impedance Matching, 156% Extended Bandwidth, and 0.38μW Power Consumption
2018 IEEE International Solid-State Circuits Conference (ISSCC), Digest of Technical Papers, Seiten: 148 - 150
Bast H, Buchhold B, Haussmann E
A Quality Evaluation of Combined Search on a Knowledge Base and Text
2018 Springer, Seiten: 19 - 26
KurzfassungWe provide a quality evaluation of KB+Text search, a deep integration of knowledge base search and standard full-text search. A knowledge base (KB) is a set of subject–predicate–object triples with a common naming scheme. The standard query language is SPARQL, where queries are essentially lists of triples with variables. KB+Text search extends this by a special occurs-with predicate, which can be used to express the co-occurrence of words in the text with mentions of entities from the knowledge base. Both pure KB search and standard full-text search are included as special cases. We evaluate the result quality of KB+Text search on three different query sets. The corpus is the full version of the English Wikipedia (2.4 billion word occurrences) combined with the YAGO knowledge base (26 million triples). We provide a web application to reproduce our evaluation, which is accessible via http://ad.informatik. uni-freiburg.de/publications.

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Nessler S, Marx M, Manoli Y
A Self-Test on Wafer Level for a MEM Gyroscope Readout Based on Delta-Sigma Modulation
2018 IEEE Transactions on Circuits and Systems - Part I (TCAS I), Band: 65, Nummer: 3, Seiten: 870 - 880
Kretschmer S, Jäger J, Vilches Exposito S, Ataman C, Zappe H
A bimodal endoscopic imager in a glass package
2018 J Micromech Microeng, Band: 28, Nummer: 10, Seite: 105009
KurzfassungWe present the first endoscopic imaging probe that combines full-field white light video microscopy and 3D optical coherence tomography (OCT) in a single miniaturized instrument. Designed as an instrument for the working channels of conventional endoscopes, the presented system has dimensions of mm3 (l × w × h) and is an important step towards practical multi-modal optical biopsy systems for clinical use. The video modality has a sensor-limited resolution and a total field of view of 10 μm and 1.17 mm in diameter, respectively. The OCT modality works in a scanned imaging arrangement and provides 3D optical tomograms with a lateral resolution of 43.5 μm. An integrated tubular piezoelectric fiber scanner is used to perform en face scanning necessary for the 3D OCT measurements. The entire system is assembled and encapsulated within a glass package fabricated via 3D laser microstructuring, a technology which addresses the major issues of micro-optic assembly precision and biocompatibility.
C.-H. Tsai, D.- H. Kuan, S. Zimmermann, J. Schoendube, A. Gross, R. Zengerle, P. Koltay
A highliy parallel microbioreactor for cell line development based on a microtiter plate with functional microfluidic lid
2018 MicroTAS 2018, 11. -15. November 2018, Kaohsiung / Taiwan
Hügle M, Dame G, Behrmann O, Rietzel R, Karthe D, Hufert F, Urban G
A lab-on-a-chip for preconcentration of bacteria and nucleic acid extraction
2018 Rsc Adv, Band: 8, Seiten: 20124 - 20130
KurzfassungTo improve detection sensitivity, molecular diagnostics require preconcentration of low concentrated samples followed by rapid nucleic acid extraction. This is usually achieved by multiple centrifugation, lysis and purification steps, for instance, using chemical reagents, spin columns or magnetic beads. These require extensive infrastructure as well as time consuming manual handling steps and are thus not suitable for point of care testing (POCT). To overcome these challenges, we developed a microfluidic chip combining free-flow electrophoretic (FFE) preconcentration (1 ml down to 5 ml) and thermoelectric lysis of bacteria as well as purification of nucleic acids by gel-electrophoresis. The integration of these techniques in a single chip is unique and enables fast, easy and space-saving sample pretreatment without the need for laboratory facilities, making it ideal for the integration into small POCT devices. A preconcentration efficiency of nearly 100% and a lysis/gel-electrophoresis efficiency of about 65% were achieved for the detection of E. coli. The genetic material was analyzed by RT-qPCR targeting the superfolder Green Fluorescent Protein (sfGFP) transcripts to quantify mRNA recovery and qPCR to determine DNA background.
Banerjee K, Rajaeipour P, Ataman C, Zappe H
A low-cost, 25-actuator electrostatic deformable mirror with polyimide membrane for adaptive optics microscopy (Best Student Paper Award)
2018 Proceedings of SPIE, Band: 10545, Seite: 105450G
Zhao P, Ataman C, Zappe H
A miniaturized camera objective with 2X optical zoom
2018 Proceedings of SPIE, Band: 10545, Seite: 1054508
Faubert P, Kondov I, Qazzazie D, Yurchenko O, Müller C
A non-noble Cr–Ni-based catalyst for the oxygen reduction reaction in alkaline polymer electrolyte fuel cells
2018 Mrs Commun, Band: 8, Nummer: 1, Seiten: 160 - 167
S. Backe, F. Balle
A novel short-time concept for fatigue life estimation of carbon (CFRP) and metal/carbon fiber reinforced polymer (MCFRP)
2018 Int J Fatigue, Band: 116, Seiten: 317 - 322

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Hoschke, Klaus, Pfaff, Aron, Fleig, Luisa, Bierdel, Marius, Jaecklein, Martin, Riedel, Werner, Hiermaier, Stefan
A parametric mesostructural approach for robust design of additive manufacturing parts
2018 Fraunhofer Direct Digital Manufacturing Conference, DDMC 2018, Fraunhofer Verlag, Stuttgart, Seite: 6
KurzfassungAdditive Manufacturing (AM) allows for production of potentially complex design solutions and motivates the use of Structural Optimization tools in product development to chase the structural limit of a design problem and its solution concept. Scratching on the limits of the material strength, design solutions can lack robustness concerning simplifications in model assumptions and uncertainties. However, the design freedom with AM can also actively be used to enhance robustness and reliability of solutions. To this end, an approach is presented that introduces Parametric Mesostructures into selective areas of the Additive Design. Structural members and coherent mechanical characteristics of these mesostructures can significantly reduce local stress peaks and can account for uncertainties, e.g. direction of load application. Their design is motivated by Structural Optimization and analysis results. Implementation of the approach is demonstrated and discussed on the example of a structural aircraft component.
Agrawal Akshay, Verschueren Robin, Diamond Steven, Boyd Stephen
A rewriting system for convex optimization problems
2018 Journal of Control and Decision, Band: 5, Nummer: 1, Seiten: 42 - 60
Fiath R, Raducanu B C, Musa S, Andrei A, Lopez C M, van Hoof C, Ruther P, Aarts A, Horvath D, Ulbert I
A silicon-based neural probe with densely-packed low-impedance titanium nitride microelectrodes for ultrahigh-resolution in vivo recordings
2018 Biosens Bioelectron, Band: 106, Seiten: 86 - 92
Lachner-Piza D, Epitashvili N, Schulze-Bonhage A, Stieglitz T, Jacobs J, Dumpelmann M
A single channel sleep-spindle detector based on multivariate classification of EEG epochs: MUSSDET.
2018 J Neurosci Meth, Band: 297, Seiten: 31 - 43
KurzfassungStudies on sleep-spindles are typically based on visual-marks performed by experts, however this process is time consuming and presents a low inter-expert agreement, causing the data to be limited in quantity and prone to bias. An automatic detector would tackle these issues by generating large amounts of objectively marked data. NEW METHOD: Our goal was to develop a sensitive, precise and robust sleep-spindle detection method. Emphasis has been placed on achieving a consistent performance across heterogeneous recordings and without the need for further parameter fine tuning. The developed detector runs on a single channel and is based on multivariate classification using a support vector machine. Scalp-electroencephalogram recordings were segmented into epochs which were then characterized by a selection of relevant and non-redundant features. The training and validation data came from the Medical Center-University of Freiburg, the test data consisted of 27 records coming from 2 public databases. RESULTS: Using a sample based assessment, 53% sensitivity, 37% precision and 96% specificity was achieved on the DREAMS database. On the MASS database, 77% sensitivity, 46% precision and 96% specificity was achieved. The developed detector performed favorably when compared to previous detectors. The classification of normalized EEG epochs in a multidimensional space, as well as the use of a validation set, allowed to objectively define a single detection threshold for all databases and participants. CONCLUSIONS: The use of the developed tool will allow increasing the data-size and statistical significance of research studies on the role of sleep-spindles.
K. Losch, S. Schuff, F. Balle, T. Beck, C. Redenbach
A stochastic microstructure model for particle reinforced aluminium matrix composites
2018 J Microsc-oxford
Z. Bagheryan, M. Trotter, L. Becherer, N. Borst, F. von Stetten
A universal approach for electrochemically DNA detection based on mediator displacement LAMP
2018 9th Euro Biosensors & Bioelectronics Congress November 29-30, 2018 Dublin, Ireland
Leonore Winterer, Sebastian Junges, Ralf Wimmer, Nils Jansen, Ufuk Topcu, Joost-Pieter Kaoten, Becker B
Abstraktions-basierte Verifikation von POMDPs im Motion-Planning-Kontext
2018 GI/ITG/GMM Workshop “Methoden und Beschreibungssprachen zur Modellierung und Verifikation von Schaltungen und Systemen”
KurzfassungWir untersuchen Pfadplanungsprobleme aus der Robotik und die Berechnung von Stra- tegien, die beweisbare Garantien für Sicherheitseigenschaften liefern. Dabei soll ein Agent mit hoher Wahrscheinlichkeit einen Zielort erreichen, ohne mit einem Hindernis zusammenzustoßen, das sich probabilistisch durch den Raum bewegt. Schwierig wird dieses Problem dadurch, dass der Agent seine Umgebung nur eingeschränkt beobachten kann. Dieses Szenario lässt sich auf na- türliche Art und Weise als ein sogenannter partiell beobachtbarer Markow-Entscheidungsprozess (POMDP) modellieren. Da viele interessante Eigenschaften auf POMDPs unentscheidbar sind, beschäftigt sich die hier vorgestellte Arbeit mit der Entwicklung einer spielbasierten Abstraktionsmethode, um für solche Pfadplanungsprobleme und Sicherheitseigenschaften gute Approximationen zu berechnen.
Vomero M, Porto Cruz MF, Zucchini E, Shabanian A, Delfino E, Carli S, Fadiga L, Ricci D, Stieglitz T
Achieving Ultra-Conformability with Polyimide-Based ECoG Arrays.
2018 Engineering in Medicine and Biology Conference (EMBC) 2018. 17-21 July 2018 . Honolulu, Hawaii, United States IEEE, Seiten: 4464 - 4467
KurzfassungMicro-electrode arrays for electrocorticography (ECoG) represent the best compromise between invasiveness and signal quality, as they are surface devices that still allow high sensitivity recordings. In this work, an assessment of different technical aspects determining the ultimate performance of ultra-conformable polyimide-based μECoG arrays is conducted via a finite element model, impedance spectroscopy measurements and recordings of sensorimotor evoked potentials (SEPs) in rats. The finite element model proves that conformability of thin-film arrays can be achieved with polyimide, a non-stretchable material, by adjusting its thickness according to the curvature of the targeted anatomical area. From the electrochemical characterization of the devices, intrinsic thermal noise of platinum and gold electrodes is estimated to be 3–5 μV. Results show that electrode size and in vitro impedance do not influence the amplitude of the recorded SEPs. However, the use of a reference on-skull (a metal screw), as compared to reference on-array (a metal electrode surrounding the recording area), provides higher-amplitude SEPs. Additionally, the incorporation of a grounded metal shield in the thin-film devices limits crosstalk between tracks and does not compromise the recording capabilities of the arrays.
Butz N, Kalita U, Kuhl M, Manoli Y
Active Charge Balancer with 6.6 to 40V Quad-Rail Power Supply Compliance for Neural Stimulators
2018 Proceedings of the IEEE International Symposium on Circuits and Systems (ISCAS)
Heizmann S, Kilias A, Ruther P, Egert U, Asplund M
Active Control of Dye Release for Neuronal Tracing Using PEDOT-PSS Coated Electrodes
2018 Ieee T Neur Sys Reh, Band: 26, Seiten: 299 - 306
Zimmermann P, Weltin A, Urban G, Kieninger J
Active Potentiometry for Dissolved Oxygen Monitoring with Platinum Electrodes
2018 Sensors, Band: 18, Nummer: 8, Seite: 2404
KurzfassungPotentiometric oxygen monitoring using platinum as the electrode material was enabled by the combination of conventional potentiometry with active prepolarization protocols, what we call active potentiometry. The obtained logarithmic transfer function is well-suited for the measurement of dissolved oxygen in biomedical applications, as the physiological oxygen concentration typically varies over several decades. We describe the application of active potentiometry in phosphate buffered salt solution at different pH and ion strength. Sensitivity was in the range of 60 mV/dec oxygen concentration; the transfer function deviated from logarithmic behavior for smaller oxygen concentration and higher ion strength of the electrolyte. Long-term stability was demonstrated for 60 h. Based on these measurement results and additional cyclic voltammetry investigations a model is discussed to explain the potential forming mechanism. The described method of active potentiometry is applicable to many different potentiometric sensors possibly enhancing sensitivity or selectivity for a specific parameter.

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Asplund M, Welle CG
Advancing Science: How Bias Holds Us Back.
2018 Neuron, Band: 99, Nummer: 4, Seiten: 635 - 639
MR Chellali, SH Nandam, S Li, MH Fawey, E Moreno-Pineda, L Velasco, T Boll, L Pastewka, R Kruk, P Gumbsch, H Hahn
Amorphous Nickel nanophases inducing ferromagnetism in equiatomic Ni-Ti alloy
2018 Acta Mater, Band: 161, Seiten: 47 - 53
KurzfassungNi50Ti50 nanometer-sized amorphous particles are prepared using inert-gas condensation followed by in situ compaction. Elemental segregation of Ni and Ti is observed in the consolidated nanostructured material. Amorphous, nearly pure Nickel (96%) nanophases form within the amorphous Ni50Ti50 alloy. Combining atom probe tomography and scanning transmission electron microscopy with computer modelling, we explore the formation process of such amorphous nanophase structure. It is shown that the Ni rich amorphous phase in the consolidated nanostructured material is responsible for the ferromagnetic behavior of the sample whereas the rapidly quenched amorphous and crystalline samples with the same chemical composition (Ni50Ti50) were found to be paramagnetic. Due to the high cooling rate obtained using the inert gas condensation technique, an exceptional control over the crystallization processes is possible, promoting the formation of various amorphous phases, which are not obtained by standard rapid quenching techniques. Our findings demonstrate the potential of amorphous metallic nanostructures as advanced technological materials, and useful magnetic compounds.
Kuehn J, Manoli Y
An Application-Specific Field-Programmable Tree Ensemble Architecture
2018 Proceedings of the International Conference on Field Programmable Logic and Applications (FPL), Seiten: 4450 - 4451
E. Kipf, S. Sané, D. Morse, T. Messinger, R. Zengerle, S. Kerzenmacher
An air-breathing enzymatic cathode with extended lifetime by continuous laccase supply
2018 Bioresource Technol, Band: 264, Seiten: 306 - 310
KurzfassungWe present a novel concept of an air-breathing enzymatic biofuel cell cathode combined with continuous supply of unpurified laccase-containing supernatant of the white-rot fungus Trametes versicolor for extended lifetime. The air-breathing cathode design obviates the need for energy-intensive active aeration. In a corresponding longterm experiment at a constant current density of 50 μA cm−2, we demonstrated an increased lifetime of 33 days (cathode potential above 0.430 V vs. SCE), independent of enzyme degradation. The obtained data suggest that theoretically a longer lifetime is feasible. However, further engineering efforts are required to prevent clogging and fouling of the supply tubes. These results represent an important step towards the realization of enzymatic biofuel cell cathodes with extended lifetime and enhanced performance.
Ralf Wimmer, Karina Wimmer, Christoph Scholl, Bernd Becker
Analysis of Incomplete Circuits Using Dependency Quantified Boolean Formulas
In: Advanced Logic Synthesis
2018, Springer International Publishing, André Inácio Reis, Rolf Drechsler, Seiten: 151 - 168, André Inácio Reis, Rolf Drechsler, ISBN: 978-3-319-67294-6
KurzfassungWe consider Dependency Quantified Boolean Formulas (DQBFs), a generalization of Quantified Boolean Formulas (QBFs), and demonstrate that DQBFs are a natural calculus to exactly express the realizability problem of incomplete combinational and sequential circuits with an arbitrary number of (combinational or bounded-memory) black boxes. In contrast to usual approaches for controller synthesis, restrictions to the interfaces of missing circuit parts in distributed architectures are strictly taken into account. We present a solution method for DQBFs together with the extraction of Skolem functions for existential variables, which can directly serve as implementations for the black boxes. First experimental results are provided.
Ralf Wimmer, Karina wimmer, Christoph Scholl, Bernd Becker
Analysis of Incomplete Circuits using Dependency Quantified Boolean Formulas
In: Advanced Logic Synthesis
2018, Springer, André Ignacio Reis and Rolf Drechsler, Seiten: 151 - 168, André Ignacio Reis and Rolf Drechsler, ISBN: 978-3-319-67294-6
Feißt M, Möller E, Wilde J
Analysis of Transient Thermal-Mechanical Stresses in Power Devices Using Test Chips and Optical Techniques
2018 10th International Conference on Integrated Power Electronics Systems (CIPS), Stuttgart, Seiten: 269 - 273
B. Gerdes, M. Breitwieser, T. Kaltenbach, M. Jehle, J. Wilde, R. Zengerle, P. Koltay, L. Riegger
Analysis of the metallic structure of microspheres produced by printing of aluminum alloys from the liquid melt
2018 Mater Res Express
KurzfassungThis work presents an analysis of the metallic structure of microspheres produced by drop-on-demand printing of the aluminum alloy AlSi12 directly printed from the liquid melt via StarJet technology. AlSi alloys are commonly used in casting processes, but microdroplets from these materials could potentially be used for additive manufacturing of metal and composite parts. Recently, several printing technologies were presented that enable the drop-on-demand printing of Al-alloy microdroplets. However, the material distribution and metallic structure inside of printed droplets is expected to be significantly different from the bulk material properties, and hardly any data on the microscopic structure of small droplets that have undergone rapid solidification has been published so far. Therefore, a microscopic in-depth study of microdroplets printed directly from the metal melt has been carried out: By the means of energy-dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), Auger electron spectroscopy (AES) and optical microscopy the material properties as well as the droplet morphology are investigated for the first time. The analysis demonstrates that the Al alloy droplets printed via StarJet technology exhibit almost no oxidation during the printing process and can therefore potentially be used for additive manufacturing of metal parts. Moreover, the metallurgical structure inside the droplets is analyzed. It exhibits significant difference to the bulk material in terms of the average secondary dendrite arm spacing.
Manuel Ruder, Alexey, Dosovitskiy, Thomas Brox
Artistic style transfer for videos and spherical images
2018 Int J Comput Vision
M.C. Wapler, F. Lemke, G. Alia, U. Wallrabe
Aspherical high-speed varifocal mirror for miniature catadioptric objectives
2018 Opt Express, Band: 26, Nummer: 5, Seiten: 6090 - 6102
A Gola, P Gumbsch, L Pastewka
Atomic-scale simulation of structure and mechanical properties of Cu(1−x)Ag(x)|Ni multilayer systems
2018 Acta Mater, Band: 150, Seiten: 236 - 247
KurzfassungWe use a combination of atom-swap Monte-Carlo (MC) and molecular dynamics (MD) to study the structure and mechanical properties of Cu(1-x)Ag(x)|Ni multilayers with 6 nm layer width for which the Ag-content is used to tune the lattice misfit. We find that the multilayers form a semi-coherent interface with a network of partial dislocations arranged in a regular triangular pattern. A combination of MC and MD was used to equilibrate Cu(1-x)Ag(x)|Ni with x = 0%, 5% and 10%. Ag does not enter the Ni-layer but segregates and precipitates from the Cu layers. We find alloying of Cu and Ni at 600 K. All these findings are in good agreement with the experimental binary phase diagrams of the Cu-Ag, Ag-Ni and Cu-Ni systems. The resulting multilayer structures were then sheared parallel and perpendicular to the normal of the bilayer interface. Initial sliding takes place at the Cu|Ni interface within the misfit dislocation network, followed by emission of partial dislocations into the Cu layer. Flow stress increases with increasing Ag content. Additional calculations of biaxial tension that suppress sliding at the heterointerface show a similar trend. Strengthening can be attributed to Ag precipitates pinning the Cu|Ni heterointerface and to the formation of sessile stacking-fault tetrahedra from the misfit dislocation network whose density increases with the concentration of Ag in the Cu layer.
Grell M, Dincer C, Le T, Lauri A, Nunez Bajo E, Kasimatis M, Barandun G, Maier SA, Cass AEG, Güder F
Autocatalytic Metallization of Fabrics Using Si Ink, for Biosensors, Batteries and Energy Harvesting
2018 Adv Funct Mater, Seite: 1804798
KurzfassungCommercially available metal inks are mainly designed for planar substrates (for example, polyethylene terephthalate foils or ceramics), and they contain hydrophobic polymer binders that fill the pores in fabrics when printed, thus resulting in hydrophobic electrodes. Here, a low‐cost binder‐free method for the metallization of woven and nonwoven fabrics is presented that preserves the 3D structure and hydrophilicity of the substrate. Metals such as Au, Ag, and Pt are grown autocatalytically, using metal salts, inside the fibrous network of fabrics at room temperature in a two‐step process, with a water‐based silicon particle ink acting as precursor. Using this method, (patterned) metallized fabrics are being enabled to be produced with low electrical resistance (less than 3.5 Ω sq⁻¹). In addition to fabrics, the method is also compatible with other 3D hydrophilic substrates such as nitrocellulose membranes. The versatility of this method is demonstrated by producing coil antennas for wireless energy harvesting, Ag–Zn batteries for energy storage, electrochemical biosensors for the detection of DNA/proteins, and as a substrate for optical sensing by surface enhanced Raman spectroscopy. In the future, this method of metallization may pave the way for new classes of high‐performance devices using low‐cost fabrics.

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P. Juelg, M. Specht, E. Kipf, M. Lehnert, C. Eckert, N. Paust, F. von Stetten, R. Zengerle, T. Hutzenlaub
Automation of qPCR based Minimal Residual Disease Monitoring by Centrifugal Microfluidics
2018 11th Symposium on minimal residual cancer, 03. – 05.05.2018, Montpellier, Frankreich
Farahani H, Wagiran R, Yurchenko O, Urban G
Barium Strontium Titanate Humidity Sensor: Impact of Doping on the Structural and Electrical Properties
2018 Eurosensors 2018, Graz, Austria Proceedings, Band: 2, Seite: 1007
KurzfassungThe influence of Mg²⁺ doping (3 mol %) on structural and humidity sensing properties of (Ba₀.₅,Sr₀.₅)TiO₃ (BST) perovskite nanocomposite were studied in details. Microstructural properties revealed the particle size, surface area, and average pore volume diminished for doped sample. For the MgO doped BST sensor, the film resistance and total impedance are changed more than four orders of magnitude in the 20–95% RH range, while BST sensor shows three orders change. The 3 mol % MgO doped sample with maximum hysteresis of 6.1 RH% and response/recovery time of about 30/80 s exhibits faster characteristics compare to pure BST sample with 6.8 RH% hysteresis and response/recovery of 41 s and 98 s, respectively. Transduction mechanism was found based on the proton transfer and further confirmed by a Bode plot and Nyquist complex impedance plane plot.
J. Streeck, C. Hank, M. Neuner, L. Gil-Carrera, M. Kokko, S. Pauliuk, A. Schaadt, S. Kerzenmacher, R. J. White
Bio-electrochemical conversion of industrial wastewater-COD combined with downstream methanol synthesis – an economic and life cycle assessment
2018 Green Chem, Band: 20, Seiten: 2742 - 2762
KurzfassungHerein, a techno-economic and environmental performance evaluation (i.e. Life Cycle Assessment (LCA)) of a 45 kW Microbial Electrolysis Cell (MEC) system is presented in the context of industrial wastewater remediation. This system produces H2 and CO2 – suitable for downstream CH3OH synthesis – based on the bio-electrochemical conversion of chemical industry wastewater with an organic content of 3.9 g(COD) L−1. A cost–benefit analysis indicates that the MEC system hardware costs, share of CO2 captured from the MEC and MEC operating current density (i.e. 1.0 mA cm−2) are crucial parameters influencing the total cost and represent areas for potential cost reductions. It was established based on the present study that MEC system operation with renewable electricity leads to H2 production costs of 4–5.7€ kg(H2) −1 (comparable to H2O electrolysis) and CH3OH production costs of 900€ t(CH3OH) −1. At the current CH3OH market prices, however, the production is currently not profitable. In turn, the cost-efficient construction of the MEC system and the use of less expensive materials could lead to improved CH3OH production economics based on this route. Our results indicate that the use of low-cost materials has greater potential with regard to cost reduction compared to reducing the internal resistance and polarization losses via the use of expensive high-performance materials in MEC construction. A complementary LCA of the proposed system, based on a “cradle-to-gate” definition, indicates that waste-based is superior to fossil-based CH3OH production with respect to global warming potential and cumulated fossil energy demand, provided the system is operated with 100% renewable electricity and CO2 sourced only from the MEC. However, with regard to the impact categories Metal Depletion and Freshwater Eutrophication Potential, the system was found to perform less satisfactorily (i.e. in comparison with fossil-based CH3OH production).
Stieglitz T, von Metzen R, Stett A
Bioelektronische Medizin-Eine Einführung in eine neue Disziplin.
VDE Health Expertenbeiträge, Band: 1, Seiten: 1 - 4, 2018
J. Peter,, L. Schumacher,, V.Landerer,, Ahmed Abdulkadir,, C.Kaller,, J. Lahr,, S. Kloeppel
Biological Factors Contributing to the Response to Cognitive Training in Mild Cognitive Impairment
2018 J Alzheimers Dis, Band: 61, Nummer: 1, Seiten: 333 - 345
K. Tröndle, S. Kartmann, L. Gutzweiler, R. Zengerle, P. Koltay, S. Zimmermann
Bioprinting with spheroids: Automated large-scale production and deposition
2018 3D Cell Culture 2018, 5. - 7. Juni 2018, Freiburg
Jonas Uhrig,, E. Rehder,, B. Fröhlich,, U. Franke,, Thomas Brox
Box2Pix: Single-Shot Instance Segmentation by Assigning Pixels to Object Boxes
2018
Sayed Herbawi A, Christ O, Kiessner L, Mottahi S, Hofmann U G, Paul O, Ruther P
CMOS Neural Probe with 1600 Close-packed Recording Sites and 32 Analog Output Channels
2018 J Microelectromech S
KurzfassungThis paper reports on 1 the development, characterization, and validation of neural probes serving the growing need of neuroscience for miniaturized tools enabling simultaneous high-resolution recording of neural activity in multiple brain areas. The probes consist of a needle-shaped shaft with a crosssection of 100 × 50 μm2 and a length of 10 or 5 mm emerging from a base with dimensions of only 0.55×1.8 mm2. The shafts carry 1600 and 800 recording sites, respectively, grouped into 50 (respectively 25) blocks of 4 × 8 electrodes with an area of 17 × 17 μm2 each, a pitch of 20 μm, and an electrode-to electrode spacing of 3 μm. The probes are fabricated using a commercial 0.18 μm CMOS process followed by dedicated metallization, passivation, and microfabrication steps. Neural signals are accessible through 32 analog output channels via a hierarchical digital addressing scheme implementing an advanced electronic depth control concept giving the option of multiple scanning modes and offering a switching time of 416 μs at a clock frequency of 1 MHz. All output channels are shielded against each other, whereby crosstalk between neighboring channels is measured to be −58 dB at 1 kHz. Absolute impedance values at 1 kHz of single IrOx and Pt electrodes are 230 ± 38 kOhm and 2.2 ± 0.3 MOhm, respectively. In vivo recordings taking advantage of the new addressing concept for high-resolution recordings from multiple brain regions were successfully performed in anesthetized rats.
S. Adhikari, V. Badilita, U. Wallrabe, J.G. Korvink
Capacitor re-design overcomes the rotation rate limit of MACS Resonators.
2018 Conc. Mag. Res. B
Dongyang C, Behrmann O, Hufert F, Dame G, Urban G
Capacity of rTth polymerase to detect RNA in the presence of various inhibitors
2018 Plos One, Band: 13, Nummer: 1, Seite: e0190041
KurzfassungThe full potential of the real-time reverse transcription polymerase chain reaction (RT-PCR) as a rapid and accurate diagnostic method is limited by DNA polymerase inhibitors as well as reverse transcriptase inhibitors which are ubiquitous in clinical samples. rTth polymerase has proven to be more resistant to DNA polymerase inhibitors present in clinical samples for DNA detection and also exhibits reverse transcriptase activity in the presence of Mn2+ ions. However, the capacity of rTth polymerase, which acts as DNA polymerase and reverse transcriptase, to detect RNA in the presence of various inhibitors has not been investigated in detail. Herein, the inhibitors originating from various clinical samples such as blood, urine, feces, bodily fluids, tissues and reagents used during nucleic acid extraction were employed to evaluate the capacity of rTth polymerase to detect RNA. The results show that the inhibitors have different inhibitory effects on the real-time RT-PCR reactions by rTth polymerase, and the inhibitory effects are concentration dependent. Additionally, the capacity of rTth polymerase to detect RNA in the presence of various inhibitors is better or at least comparable with its capacity to detect DNA in the presence of various inhibitors. As a consequence, RNA may be directly detected in the presence of co-purified inhibitors or even directly from crude clinical samples by rTth polymerase.

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J. Hess, S. Yazar, N. Paust, R. Zengerle, T. Hutzenlaub
Capillary Valve for Microfluidic Foil Chips Fabricated by Micro-Milled Metal Master Tools
2018 MicroTAS 2018, 11. -15. November 2018, Kaohsiung / Taiwan
F. Hegge, R. Moroni, E. Wright, J. Sharman, S. Thiele, S. Vierrath
Catalyst Support Ageing of Polymer Electrolyte Fuel Cells Investigated with Tomography
2018 69th Annual Meeting of the International Society of Electrochemistry (ISE), Bologna/Italy, 02. – 07.09.2018
Kurzfassung69th Annual Meeting of the International Society of Electrochemistry (ISE), Bologna/Italy, 02. – 07.09.2018
V Sandfort, J Goldschmidt, J Wöllenstein, S Palzer
Cavity-Enhanced Raman Spectroscopy for Food Chain Management
2018 Sensors-basel, Band: 18, Nummer: 3, Seite: 709
KurzfassungComprehensive food chain management requires the monitoring of many parameters including temperature, humidity, and multiple gases. The latter is highly challenging because no low-cost technology for the simultaneous chemical analysis of multiple gaseous components currently exists. This contribution proposes the use of cavity enhanced Raman spectroscopy to enable online monitoring of all relevant components using a single laser source. A laboratory scale setup is presented and characterized in detail. Power enhancement of the pump light is achieved in an optical resonator with a Finesse exceeding 2500. A simulation for the light scattering behavior shows the influence of polarization on the spatial distribution of the Raman scattered light. The setup is also used to measure three relevant showcase gases to demonstrate the feasibility of the approach, including carbon dioxide, oxygen and ethene.
N. Paust
Centrifugal Microfluidics:Unique operations enabled by artificial buoyancy
2018 Lab-on-a-Chip and Microfluidics Europe 2018, Rotterdam/Niederlande, 05. - 06.06.2018
K. Mitsakakis, W.E. Kaman, G. Elshout, M. Specht, J.P. Hays
Challenges in identifying antibiotic resistance targets for point-of-care diagnostics in general practice
2018 Future Microbiol, Band: 13, Nummer: 10, Seiten: 1157 - 1164
KurzfassungGeneral practitioners stand at the front line of healthcare provision and have a pivotal role in the fight against increasing antibiotic resistance. In this respect, targeted antibiotic prescribing by general practitioners would help reduce the unnecessary use of antibiotics, leading to reduced treatment failures, fewer side-effects for patients and a reduction in the (global) spread of antibiotic resistances. Current ‘gold standard’ antibiotic resistance detection strategies tend to be slow, taking up to 48 h to obtain a result, although the implementation of point-of-care testing by general practitioners could help achieve the goal of targeted antibiotic prescribing practices. However, deciding on which antibiotic resistances to include in a point-of-care diagnostic is not a trivial task, as outlined in this publication.
S Khanal, A Gujrati, SB Vishnubhotla, P Nowakowski, C Bonifacio, L Pastewka, TDB Jacobs
Characterization of small-scale surface topography using transmission electron microscopy
2018 Surf Topogr-metrol, Band: 6, Seite: 045004
KurzfassungMulti-scale surface topography is critical to surface function, yet the very smallest scales are not accessible with conventional measurement techniques. Here we demonstrate two separate approaches for measuring small-scale topography in a transmission electron microscope (TEM). The first technique harnesses "conventional" methods for preparation of a TEM cross-section, and presents how these methods may be modified to ensure the preservation of the original surface. The second technique involves the deposition of the material of interest on a pre-fabricated substrate. Both techniques enable the observation and quantification of surface topography with Ångström-scale resolution. Then, using electron energy loss spectroscopy (EELS) to quantify the sample thickness, we demonstrate that there is no systematic effect of thickness on the statistical measurements of roughness. This result was verified using mathematical simulations of artificial surfaces with varying thickness. The proposed explanation is that increasing the side-view thickness of a randomly rough surface may change which specific features are sampled, but does not significantly alter the character (e.g., root-mean-square (RMS) values and power spectral density (PSD)) of the measured topography. Taken together, this work establishes a new approach to topography characterization, which fills in a critical gap in conventional approaches: i.e., the measurement of smallest-scale topography.
Bruno B, Fahmy A, Stürmer M, Wallrabe U, Wapler M
Characterizing Piezoceramic Materials in High Electric Field Actuator Applications
2018 ACTUATOR 2018, 16th Int. Conference on New Actuators, Bremen, Germany , Seiten: 416 - 419
Feldmann Frank, Nogay Gizem, Löper Philipp, Young David, Lee Benjamin, Stradins Paul, Hermle Martin, Glunz Stefan
Charge carrier transport mechanisms of passivating contacts studied by temperature-dependent J-V measurements
2018 Solar Energy Materials and Solar Cells, Band: 178, Seite: 15–19
KurzfassungThe charge carrier transport mechanism of passivating contacts which feature an ultra-thin oxide layer is investigated by studying temperature-dependent current-voltage characteristics. 4-Terminal dark J-V measurements at low temperatures reveal non-linear J-V characteristics of passivating contacts with a homogeneously grown silicon oxide, which result in an exponential increase in contact resistance towards lower temperature. The attempt to describe the R(T) characteristic solely by thermionic emission of charge carriers across an energy barrier leads to a significant underestimation of the resistance by several orders of magnitude. However, the data can be described properly with the metal-insulator-semiconductor (MIS) theory if tunneling of charge carriers through the silicon oxide layer is taken into account. Furthermore, temperature-dependent light J-V characteristics of solar cells featuring passivating contacts at the rear revealed a FF drop at T<205 K, which is near the onset temperature of the exponential increase in contact resistivity.
Z Li, L Pastewka, I Szlufarska
Chemical aging of large-scale randomly rough frictional contacts
2018 Phys Rev E, Band: 98, Seite: 023001
KurzfassungIt has been shown that contact aging due to chemical reactions in single asperity contacts can have a significant effect on friction. However, it is currently unknown how chemically induced contact aging of friction depends on roughness that is typically encountered in macroscopic rough contacts. Here we develop an approach that brings together a kinetic Monte Carlo model of chemical aging with a contact mechanics model of rough surfaces based on the boundary element method to determine the magnitude of chemical aging in silica-silica contacts with random roughness. Our multiscale model predicts that chemical aging for randomly rough contacts has a logarithmic dependence on time. It also shows that friction aging switches from a linear to a nonlinear dependence on the applied load as the load increase. We discover that surface roughness affects the aging behavior primarily by modifying the real contact area and the local contact pressure, whereas the effect of contact morphology is relatively small. Our results demonstrate how understanding of chemical aging can be translated from studies of single asperity contacts to macroscopic rough contacts.
J. De Fauw,, J. Ledsam,, B. Romera-Paredes,, S. Nikolov,, N. Tomasev,, S. Blackwell,, H. Askham,, X. Glorot,, B. O’Donoghue,, D. Visentin,, G. van den Driessche,, B. Lakshminarayanan,, C. Meyer,, F. Mackinder,, S. Bouton,, K. Ayoub,, R. Chopra,, D. King,, A. Karthikesalingam,, C. Hughes,, R. Raine,, J. Hughes,, D. Sim,, C. Egan,, A. Tufail,, H. Montgomery,, D. Hassabis,, G. Rees,, T. Back,, P. Khaw,, M. Suleyman,, J. Cornebise,, P. Keane,, Olaf Ronneberger
Clinically applicable deep learning for diagnosis and referral in retinal disease
2018 Nat Med, Band: 24, Nummer: 9, Seiten: 1342 - 1350
KurzfassungThe volume and complexity of diagnostic imaging is increasing at a pace faster than the availability of human expertise to interpret it. Artificial intelligence has shown great promise in classifying two-dimensional photographs of some common diseases and typically relies on databases of millions of annotated images. Until now, the challenge of reaching the performance of expert clinicians in a real-world clinical pathway with three-dimensional diagnostic scans has remained unsolved. Here, we apply a novel deep learning architecture to a clinically heterogeneous set of three-dimensional optical coherence tomography scans from patients referred to a major eye hospital. We demonstrate performance in making a referral recommendation that reaches or exceeds that of experts on a range of sight-threatening retinal diseases after training on only 14,884 scans. Moreover, we demonstrate that the tissue segmentations produced by our architecture act as a device-independent representation; referral accuracy is maintained when using tissue segmentations from a different type of device. Our work removes previous barriers to wider clinical use without prohibitive training data requirements across multiple pathologies in a real-world setting.

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Daniel Kuhner, Johannes Aldinger, Felix Burget, Moritz Göbelbecker, Wolfram Burgard, Bernhard Nebel
Closed-Loop Robot Task Planning Based on Referring Expressions
2018 IEEE/RSJ International Conference on Intelligent Robots and Systems, Madrid 2018 Proc. of IEEE/RSJ International Conference on Intelligent Robots and Systems
KurzfassungIncreasing the accessibility of autonomous robots also for inexperienced users requires user-friendly and highlevel control opportunities of robotic systems. While automated planning is able to decompose a complex task into a sequence of steps which reaches an intended goal, it is difficult to formulate such a goal without knowing the internals of the planning system and the exact capabilities of the robot. This becomes even more important in dynamic environments in which manipulable objects are subject to change. In this paper, we present an adaptive control interface which allows users to specify goals based on an internal world model by incrementally building referring expressions to the objects in the world. We consider fetch-and-carry tasks and automatically deduce potential high-level goals from the world model to make them available to the user. Based on its perceptions our system can react to changes in the environment by adapting the goal formulation within the domain-independent planning system.
L Engel, K Tarantik, C Pannek, J Wöllenstein
Colorimetric Detection of Hydrogen Sulfide in Ambient Air
2018 Multidisciplinary Digital Publishing Institute Proceedings , Band: 2, Nummer: 13, Seite: 804
KurzfassungWe present a fast method to monitor hydrogen sulfide (H 2 S) in ambient air based on a visible color change. Therefore, an immobilized copper (II) complex of the azo dye 1-(2-pyridylazo)-2-naphtol (H-PAN) was synthesized and prepared in a matrix for screen printing. Different materials, reaching from opaque paper to transparent foils served as substrate. The reaction of the copper (II) complex (Cu-PAN) to the target gas H 2 S was measured in reflection via UV/VIS spectroscopy.
K Schmitt, KR Tarantik, C Pannek, J Wöllenstein
Colorimetric Materials for Fire Gas Detection—A Review
2018 Chemosensors, Band: 6, Nummer: 2, Seite: 14
KurzfassungThe damage caused by outbreaks of fire continues to be enormous despite ongoing improvements in fire detection and fighting. Therefore, the detection of fires at the earliest possible stage is essential. The latest developments in fire detection devices include the addition of carbon monoxide (CO) or temperature sensors into the widespread smoke detectors, but also alternative solutions are searched for. Advantageous is the direct detection of the most relevant fire gases CO and nitrogen dioxide (NO2), because they are produced very early in a developing fire. A sensitive, selective, and low-cost method to detect these gases is the use of colorimetric materials combined with a compact optical readout. In this review, we take account of recent developments in this research field and provide a comprehensive overview on suitable materials for CO and NO2 detection in fire gas sensing and first steps towards novel fire gas detectors.
Tobias Seufert, Christoph Scholl
Combining PDR and Reverse PDR for Hardware Model Checking
2018 Conference on Design, Automation and Test in Europe (DATE)
KurzfassungIn the last few years IC3 resp. PDR attracted a lot of attention as a SAT-based hardware verification approach without needing to unroll the transition relation as in Bounded Model Checking (BMC). Motivated by different strengths of forward and backward traversal already observed in BDD based model checking and by an exponential complexity gap between original PDR and its reverted counterpart ‘Reverse PDR’ (which starts its analysis with the initial states instead of the unsafe states as in the original PDR), we take a closer look at Reverse PDR and we present a combined forward/backward version of PDR that inherits the advantages of both original and Reverse PDR. Our experimental results on benchmarks from the Hardware Model Checking Competition demonstrate clear benefits of the combined approach.
A Gujrati, SR Khanal, L Pastewka, TDB Jacobs
Combining TEM, AFM, and profilometry for quantitative topography characterization across all scales
2018 Acs Appl Mater Inter, Band: 10, Nummer: 34, Seiten: 29169 - 29178
KurzfassungSurface roughness affects the functional properties of surfaces, including adhesion, friction, hydrophobicity, biological response, and electrical and thermal transport properties. However, experimental investigations to quantify these links are often inconclusive, because surfaces are fractal-like and the values of measured roughness parameters depend on measurement size. Here we demonstrate the characterization of topography of an ultrananocrystalline diamond (UNCD) surface at the Ångström-scale using transmission electron microscopy (TEM), as well as its combination with conventional techniques to achieve a comprehensive surface description spanning eight orders of magnitude in size. We performed more than 100 individual measurements of the nanodiamond film using both TEM and conventional techniques (stylus profilometry and atomic force microscopy). While individual measurements of root-mean-square (RMS) height, RMS slope, and RMS curvature vary by orders of magnitude, we combine the various techniques using the power spectral density (PSD) and use this to compute scale-independent parameters. This analysis reveals that “smooth” UNCD surfaces have an RMS slope greater than one, even larger than the slope of the Austrian Alps when measured on the scale of a human step. This approach of comprehensive multi-scale roughness characterization, measured with Ångström-scale detail, will enable the systematic evaluation and optimization of other technologically relevant surfaces, as well as systematic testing of the many analytical and numerical models for the behavior of rough surfaces.
Bleitner A, Goeppert J, Lotze N, Keller M, Manoli Y
Comparison and Optimization of the Minimum Supply Voltage of Schmitt Trigger Gates versus CMOS Gates under Process Variations
2018 GMM-Fb. 91: ANALOG 2018, Seiten: 111 - 116
Valle G, Petrini FM, Strauss I, Iberite F, D'Anna E, Granata G, Controzzi M, Cipriani C, Stieglitz T, Rossini PM, Mazzoni A, Raspopovic S, Micera S
Comparison of linear frequency and amplitude modulation for intraneural sensory feedback in bidirectional hand prostheses.
2018 Sci Rep-uk, Band: 8, Nummer: 1, Seite: 16666
KurzfassungRecent studies have shown that direct nerve stimulation can be used to provide sensory feedback to hand amputees. The intensity of the elicited sensations can be modulated using the amplitude or frequency of the injected stimuli. However, a comprehensive comparison of the effects of these two encoding strategies on the amputees’ ability to control a prosthesis has not been performed. In this paper, we assessed the performance of two trans-radial amputees controlling a myoelectric hand prosthesis while receiving grip force sensory feedback encoded using either linear modulation of amplitude (LAM) or linear modulation of frequency (LFM) of direct nerve stimulation (namely, bidirectional prostheses). Both subjects achieved similar and significantly above-chance performance when they were asked to exploit LAM or LFM in different tasks. The feedbacks allowed them to discriminate, during manipulation through the robotic hand, objects of different compliances and shapes or different placements on the prosthesis. Similar high performances were obtained when they were asked to apply different levels of force in a random order on a dynamometer using LAM or LFM. In contrast, only the LAM strategy allowed the subjects to continuously modulate the grip pressure on the dynamometer. Furthermore, when long-lasting trains of stimulation were delivered, LFM strategy generated a very fast adaptation phenomenon in the subjects, which caused them to stop perceiving the restored sensations. Both encoding approaches were perceived as very different from the touch feelings of the healthy limb (natural). These results suggest that the choice of specific sensory feedback encodings can have an effect on user performance while grasping. In addition, our results invite the development of new approaches to provide more natural sensory feelings to the users, which could be addressed by a more biomimetic strategy in the future.
VL Deringer, MA Caro, R Jana, A Aarva, SR Elliott, T Laurila, G Csányi, L Pastewka
Computational surface chemistry of tetrahedral amorphous Carbon by combining machine learning and DFT
2018 Chem Mater
KurzfassungTetrahedral amorphous carbon (ta-C) is widely used for coatings due to its superior mechanical properties and has been suggested as an electrode material for detecting biomolecules. Despite extensive research, however, the complex atomic-scale structures and chemical reactivity of ta-C surfaces are incompletely understood. Here, we combine machine learning, density-functional tight-binding, and density-functional theory simulations to shed new light on this long-standing problem. We make atomistic models of ta-C surfaces, characterize them by local structural fingerprints, and provide a library of structures at different system sizes. We then move beyond the pure element and exemplify how chemical reactivity (hydrogenation and oxidation) can be modeled at the surfaces. Our work opens up new perspectives for modeling the surfaces and interfaces of amorphous solids, which will advance studies of ta-C and other functional materials.
Subbiah N, Bruckner G, Beltran Ramirez K, Wilde J
Concept and Implementation of High-Temperature Pressure Sensor Package up to 500 °C
2018 19th ITG/GMA-Symposium, Sensors and Measuring Systems (SENSOR), Nürnberg, Seiten: 55 - 60
A Klemenz, A Gola, M Moseler, L Pastewka
Contact mechanics of graphene-covered metal surfaces
2018 Appl Phys Lett, Band: 112, Seite: 061601
KurzfassungWe carry out molecular statics simulations of the indentation of bare and graphene-covered Pt (111) surfaces with smooth and rough indenters of radius 1.5 to 10 nm. Our simulations show that the plastic yield of bare surfaces strongly depends on atomic-scale indenter roughness such as terraces or amorphous disorder. Covering surfaces with graphene regularizes this response to the results obtained for ideally smooth indenters. Our results suggest that graphene monolayers and other 2D materials mitigate the effect of roughness, which could be exploited to improve the fidelity of experiments that probe the mechanical properties of interfaces.
Jia Y, Hanka K, Zawilski K, Schunemann P, Buse K, Breunig I
Continuous-wave whispering-gallery optical parametric oscillator based on CdSiP₂
2018 Opt Express, Band: 26, Nummer: 8, Seiten: 10833 - 10841
KurzfassungContinuous-wave (cw) optical parametric oscillators (OPOs) are ideally suited for applications, for example high-resolution spectroscopy, that need coherent sources combining narrow-linewidth emission with good wavelength tunability. Here, we demonstrate for the first time cw OPOs based on a millimeter-sized whispering gallery resonator (WGR) made of cadmium silicon phosphide (CdSiP₂). By employing a compact laser diode at 1.57-μm wavelength for pumping, a cw OPO with wavelength tunability from 2.3 μm to 5.1 μm is realized based on such a resonator. The oscillation thresholds are in the milliwatt range. The maximum total power conversion efficiency reaches more than 15%. The intrinsic quality factor at 1.57 μm is determined to be 3.5 × 10⁶. This work suggests that CdSiP₂ is a very promising alternative for constructing mid-infrared parametric devices.
Voglstätter, C., Weidlich, A., Fischer, D., Schmidinger, J.
Control algorithms for electrolyzers - Hydrogen from green electricity
2018 BKW, Band: 70, Nummer: 7/8, Seiten: 36 - 39
KurzfassungIn 2017, the share of renewables in power generation in Germany was around 33 %. By 2030, according to the will of the federal government, it should be as high as 65 %. A large proportion of electricity from wind and solar energy will in future require electricity storage. Particularly promising is the conversion to hydrogen. Research, industry and the energy sector are currently driving forward the development and use of water electrolysers. The Fraunhofer Institute for Solar Energy Systems ISE and the University of Applied Sciences Offenburg, in cooperation with the energy provider badenova and the gas network operator bnNetz have developed operating management algorithms for electrolyzers and tested them at research facilities. Within the project, the integration of hydrogen into municipal gas and electricity grids and into a local energy grid could be tested taking into account the current regulations and economic constraints. Thereby, the partners have laid important foundations for the use of the energy carrier hydrogen.
Werner C, Sturman B, Podivilov E, Kini Manjeshwar S, Buse K, Breunig I
Control of mode anticrossings in whispering gallery microresonators
2018 Opt Express, Band: 26, Nummer: 2, Seiten: 762 - 771
KurzfassungOptical microresonators attract strong interest because of exciting effects and applications ranging from sensing of single atoms and molecules to quantum and nonlinear optics. For all this, control and tuning of the discrete resonances are vital. In resonators made of anisotropic materials that are beneficial for nonlinear-optical applications, anticrossings of ordinarily (o) and extraordinarily (e) polarized modes occur regularly. This effect is badly understood and harmful for mode control and tuning. We show that the anticrossings are inherent in the o- and e-modes because of the vectorial properties of Maxwell’s equations. Within a novel pertubative approach employing a strong localization of the modes near the resonator rim, we have quantified the anticrossings. The values of avoidance gaps strongly exceeding the linewidths and selection rules for the interacting modes are predicted. The inferred values of the avoidance gaps are confirmed experimentally in resonators made of lithium niobate. Furthermore, based on theory, we have eliminated the anticrossings completely by spatially-controlled introduction of defects. This paves the way for unperturbed tuning of anisotropic microresonators.
Jan Wülfing, Sreedhar Saseendran Kumar, Joschka Boedecker, Martin Riedmiller, Ulrich Egert
Controlling Biological Neural Networks with Deep Reinforcement Learning
2018 European Symposium on Artificial Neural Networks, Computational Intelligence and Machine Learning

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Wülfing J, Kumar S S, Boedecker J, Riedmiller M, Egert U
Controlling Biological Neural Networks with Deep Reinforcement Learning
2018 i6doc.com publ., Seiten: 355 - 360
K. Mitsakakis, S. Hin, P. Müller, N. Wipf, E. Thomsen, M. Coleman, R. Zengerle, J. Vontas, K. Mavridis
Converging Human and Malaria Vector Diagnostics with Data Management towards an Integrated Holistic One Health Approach
2018 International Journal of Environmental Research and Public Health, Band: 15, Nummer: 2, Seite: E259
KurzfassungMonitoring malaria prevalence in humans, as well as vector populations, for the presence of Plasmodium, is an integral component of effective malaria control, and eventually, elimination. In the field of human diagnostics, a major challenge is the ability to define, precisely, the causative agent of fever, thereby differentiating among several candidate (also non-malaria) febrile diseases. This requires genetic-based pathogen identification and multiplexed analysis, which, in combination, are hardly provided by the current gold standard diagnostic tools. In the field of vectors, an essential component of control programs is the detection of Plasmodium species within its mosquito vectors, particularly in the salivary glands, where the infective sporozoites reside. In addition, the identification of species composition and insecticide resistance alleles within vector populations is a primary task in routine monitoring activities, aiming to support control efforts. In this context, the use of converging diagnostics is highly desirable for providing comprehensive information, including differential fever diagnosis in humans, and mosquito species composition, infection status, and resistance to insecticides of vectors. Nevertheless, the two fields of human diagnostics and vector control are rarely combined, both at the diagnostic and at the data management end, resulting in fragmented data and mis- or non-communication between various stakeholders. To this direction, molecular technologies, their integration in automated platforms, and the co-assessment of data from multiple diagnostic sources through information and communication technologies are possible pathways towards a unified human vector approach.
Lima F, Mescheder U, Müller C, Reinecke H
Copper electrodeposition on silicon electrodes
2018 Int J Surf Sci Eng, Band: 12, Nummer: 2
Schlachtberger D, Brown T, Schäfer M, Schramm S, Greiner M
Cost optimal scenarios of a future highly renewable European electricity system: Exploring the influence of weather data, cost parameters and policy constraints
2018 Energy, Band: 163, Seiten: 100 - 114
KurzfassungCost optimal scenarios derived from models of a highly renewable electricity system depend on the specific input data, cost assumptions and system constraints. Here this influence is studied using a techno-economic optimisation model for a networked system of 30 European countries, taking into account the capacity investment and operation of wind, solar, hydroelectricity, natural gas power gen- eration, transmission, and different storage options. A considerable robustness of total system costs to the input weather data and to moderate changes in the cost assumptions is observed. Flat directions in the optimisation landscape around cost-optimal configurations often allow system planners to choose between different technology options without a significant increase in total costs, for instance by replacing onshore with offshore wind power capacity in case of public acceptance issues. Exploring a range of carbon dioxide emission limits shows that for scenarios with moderate transmission expansion, a reduction of around 57% compared to 1990 levels is already cost optimal. For stricter carbon dioxide limits, power generated from gas turbines is at first replaced by generation from increasing renewable capacities. Non-hydro storage capacities are only built for low-emission scenarios, in order to provide the necessary flexibility to meet peaks in the residual load.

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L. Minkova,, S. Gregory,, R. Scahill,, Ahmed Abdulkadir,, C. Kaller,, J. Peter,, J. Long,, J. Stout,, R. Reilmann,, R. Roos, A. Durr, B. Leavit, S. Tabrizi, S. Kloeppel
Cross-sectional and longitudinal voxel-based grey matter asymmetries in Huntingtons disease
2018 Neuroimage, Band: 17, Seiten: 312 - 324
M Azhar, S Shakil, A Greiner, D Kauzlaric, JG Korvink
DPD enables mesoscopic MRI simulation of slow flow
2018 Microfluid Nanofluid, Band: 22, Nummer: 5, Seite: 55
KurzfassungWe present a novel method to simulate magnetic resonance imaging (MRI) for the assessment of slow flow at Reynolds number Re≈0.02. We couple Bloch equations with dissipative particle dynamics (DPD) to study the effect of flow dynamics at the mesoscopic level on acquired MR images. The Bloch equations are used to propagate the evolution of the magnetization of particles while their trajectories are being computed simultaneously based on DPD interaction forces. The magnetic resonance assessment of fluid velocities is performed using a phase-contrast MRI technique, implemented by a spin echo single-sided bipolar gradient sequence. The computational cost for simulating the fluid flow is successfully reduced by an efficient implementation of a vectorized isochromat algorithm. We demonstrate successful simulation of laminar flow, flow with diffusion effects, and flow around an obstacle. The method can be used to simulate convective and diffusive flow MRI experiments at the mesoscopic level.
M Azhar, S Shakil, A Greiner, D Kauzlaric, JG Korvink
DPD of diffusion-weighted MRI
2018 Comput Fluids, Band: 172, Seiten: 467 - 473
KurzfassungDiffusion weighted magnetic resonance imaging (DW-MRI) experiments can be simulated by coupling dissipative particle dynamics (DPD) with Bloch equations. DPD gives hydrodynamics with thermal fluctuations at a well-defined temperature by introducing momentum conserving particle interaction forces and a fluctuation dissipation theorem. The Bloch equations are a set of differential equations that describe the evolution of nuclear magnetization as a function of time. Here we successfully simulate DW-MRI by using the solution of Bloch equations for each DPD particle while computing its trajectories through DPD forces. To this end, a spin echo sequence combined with different diffusion-weighting gradients was implemented and tested for the diffusion of a fluid bound by different diffusion regimes. Fluid confinement was easily incorporated, which enabled investigating different diffusion regimes and the performance of different pulse sequences. The three different sequences applied were: spin echo single-sided bipolar gradient, spin echo two-sided bipolar gradient and spin echo uni-polar gradient; and the three imaged diffusion regimes of interest were: free diffusion, localization and motional narrowing.
Gabriel Leivas Oliveira,, W. Burgard,, Thomas Brox
DPDB-Net: Exploiting Dense Connections for Convolutional Encoders
2018 IEEE

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A. Middleton,, C. Dal Bosco,, P. Chlap,, Robert Bensch,, H. Harz,, F. Ren,, S. Bergmann,, S. Wend,, W. Weber,, K. Hayashi,, M. Zurbriggen,, R. Uhl,, Olaf Ronneberger,, K. Palme,, C. Fleck,, A. Dovzhenko
Data-Driven Modeling of Intracellular Auxin Fluxes Indicates a Dominant Role of the ER in Controlling Nuclear Auxin Uptake
2018 Cell Rep, Band: 22, Nummer: 11, Seiten: 3044 - 3057
Christoph Scholl, Ralf Wimmer
Dependency Quantified Boolean Formulas: An Overview of Solution Methods and Applications
2018 13th International Conference on Theory and Applications of Satisfiability Testing (SAT), Springer-Verlag, Nummer: 10929, Seiten: 3 - 16
KurzfassungDependency quantified Boolean formulas (DQBFs) as a generalization of quantified Boolean formulas (QBFs) have received considerable attention in research during the last years. Here we give an overview of the solution methods developed for DQBF so far. The exposition is complemented with the discussion of various applications that can be handled with DQBF solving.
Pascal Raiola, Michael A. Kochte, Ahmed Atteya, Laura Rodríguez Gómez, Hans-Joachim Wunderlich, Bernd Becker, Matthias Sauer
Design of Reconfigurable Scan Networks for Secure Data Transmission
2018 GI/ITG Workshop “Testmethoden und Zuverlässigkeit von Schaltungen und Systemen”
Cojocaru Ludmila, Wienands Karl, Kim Tae, Uchida Satoshi, Bett Alexander, Rafizadeh Saeid, Goldschmidt Jan, Glunz Stefan
Detailed Investigation of Evaporated Perovskite Absorbers with High Crystal Quality on Different Substrates
2018 ACS applied materials & interfaces
KurzfassungDual-source vapor-phase deposition enables low-temperature fabrication of high-performance planar structure perovskite (CH3NH3PbI3) solar cells (PSCs), applicable in tandem devices or for industrial production with high homogeneity. Herein, we report low-temperature fabrication of high-efficiency PSCs by dual-source vapor-phase deposition and significance of TiO2 surface modification with [6,6]-phenyl C61 butyric acid methyl ester (PCBM) on cell performance. Co-evaporation of PbI2 and CH3NH3I, as confirmed by X-ray diffraction and high-resolution transmission electron microscopy analyses, results in CH3NH3PbI3 layers with a well-crystallized tetragonal phase formed on both TiO2 and TiO2/PCBM electron-transport layers (ETLs). The devices with PCBM interlayer between TiO2 and CH3NH3PbI3 showed remarkably higher performance than those with TiO2 only, which was attributed to enhance charge extraction and reduced recombination at the TiO2/PCBM/CH3NH3PbI3 interface. The devices composed of evaporated CH3NH3PbI3 on top of the TiO2/PCBM and [2,2',7,7'-tetrakis( N, N-di- p-methoxyphenyl-amine)-9,9'-spirobifluorene] (Spiro-OMeTAD) as hole-transport material demonstrated power conversion efficiencies of 17.1% (reverse scan) and 13.4% (forward scan) with stabilized efficiency of over 16%, which is, to the best of our knowledge, the highest efficiency reported for evaporated perovskite solar cells using low-temperature fabrication method involving compact TiO2 layer as ETL. Furthermore, we show that this process can be used to deposit a CH3NH3PbI3 layer on top of a textured silicon substrate, which is the first step for preparing perovskite-silicon tandem devices with enhanced antireflection and light-trapping properties.
Bosh N., Mozaffari-Jovein H., Müller C
Determination of Triaxial Residual Stress in Plasma-Sprayed Hydroxyapatite (HAp) Deposited on Titanium Substrate by X-ray Diffraction
2018 J Therm Spray Techn, Band: 27, Nummer: 130, Seiten: 1 - 13
KurzfassungMeasurement of residual stress in plasma-sprayed coating is of key importance to optimize their microstructure and mechanical properties. In this study, the x-ray diffraction analysis was carried out using the sin2ψ method to evaluate the residual stress distribution of hydroxyapatite (HAp) coatings produced on titanium substrate by atmospheric plasma spraying (APS) and vacuum plasma spraying (VPS). The sin2ψ method measured strains at different tilt ψ and rotating φ angles around the specimen surface normal. A non-uniform and inhomogeneous stress distribution was present in the both coatings. The measured strain εψφ is plotted versus sin2ψ, showing a nonlinear (elliptical) behavior, which indicates the presence of inhomogeneous triaxial stress distributions within coating, due to the crystalline anisotropy, inhomogeneous cooling rate or solidification of the molten particles. The normal stress values within both HAp coatings produced were found to be tensile in nature, but the values of tensile stresses are significantly higher in APS coating than those values obtained for VPS coating.
Mohsen Ghaffari, Fabian Kuhn, Yannic Maus, Jara Uitto
Deterministic Distributed Edge-Coloring with Fewer Colors
2018 ACM Symposium on Theory of Computing (STOC) 2018.
KurzfassungWe present a deterministic distributed algorithm, in the $\LOCAL$ model, that computes a $(1+o(1))\Delta$-edge-coloring in polylogarithmic-time, so long as the maximum degree $\Delta=\tilde{\Omega}(\log n)$. For smaller $\Delta$, we give a polylogarithmic-time $3\Delta/2$-edge-coloring. These are the first deterministic algorithms to go below the natural barrier of $2\Delta-1$ colors, and they improve significantly on the recent polylogarithmic-time $(2\Delta-1)(1+o(1))$-edge-coloring of Ghaffari and Su [SODA'17] and the $(2\Delta-1)$-edge-coloring of Fischer, Ghaffari, and Kuhn [FOCS'17], positively answering the main open question of the latter. The key technical ingredient of our algorithm is a simple and novel gradual packing of judiciously chosen near-maximum matchings, each of which becomes one of the color classes.
Fabian Kuhn, Yannic Maus, Simon Weidner
Deterministic Distributed Ruling Sets of Line Graphs
2018 Int. Coll. on Structural Information and Communication Complexity (SIROCCO)
KurzfassungAn $(\alpha,\beta)$-ruling set of a graph $G=(V,E)$ is a set $R\subseteq V$ such that for any node $v\in V$ there is a node $u\in R$ in distance at most $\beta$ from $v$ and such that any two nodes in $R$ are at distance at least $\alpha$ from each other. The concept of ruling sets can naturally be extended to edges, i.e., a subset $F\subseteq E$ is an \emph{$(\alpha,\beta)$-ruling edge set} of a graph $G=(V,E)$ if the corresponding nodes form an $(\alpha,\beta)$-ruling set in the line graph of $G$. This paper presents a simple deterministic, distributed algorithm, in the CONGEST ~ model, for computing $(2,2)$-ruling edge sets in $O(\logstar n)$ rounds. Furthermore, we extend the algorithm to compute ruling sets of graphs with bounded \emph{diversity}. Roughly speaking, the diversity of a graph is the maximum number of maximal cliques a vertex belongs to. We devise $(2,O(\diversity))$-ruling sets on graphs with diversity $\diversity$ in $O(\diversity+\logstar n)$ rounds. This also implies a fast, deterministic $(2,O(\rank))$-ruling edge set algorithm for hypergraphs with rank at most \rank. Furthermore, we provide a ruling set algorithm for general graphs that for any $B\geq 2$ computes an $\big(\alpha, \alpha \ceil{\log_B n}\big)$-ruling set in $O(\alpha \cdot B \cdot \log_B n)$ rounds in the CONGEST model. The algorithm can be modified to compute a $\big(2, \beta \big)$-ruling set in $O(\beta \degree^{2/\beta} + \logstar n)$ rounds in the CONGEST model, which matches the currently best known such algorithm in the more general LOCAL model.
S. H. Moosavi, M. Kroener, M. Frei, F. Frick, S. Kerzenmacher, P. Woias
Development of a TEM Compatible Nanowire Characterization Platform With Self-forming Contacts
2018 Ieee T Semiconduct M, Band: 31, Nummer: 1, Seiten: 1 - 10
KurzfassungA nanowire characterization platform is designed and fabricated in MEMS-technology for the thermoelectric and structural characterization of single nanowires. The latter is achieved by making the chip compatible to TEM holder, by restricting its thickness to less than 160μm and its diagonal dimensions to less than 3mm. Two different fabrication technologies are presented for the realization of such platform, based on a design reproducing the functional requirements. Our first fabrication technique is based on ICP etching, using (100)-silicon wafers, and a subsequent rear grinding. However, as the design includes a vertical wall trench structures, ICP etching of such deep recesses is time-consuming and expensive. Therefore, a second fabrication process is developed, making use of wet-etched (110)-silicon. With these substrates a challenge arises from the intersection of inclined {111} facets. To solve this natural limitation, we introduce a novel fabrication process. Our technique relies on damaging the intersecting {111} planes, to make them etchable again and to produce deeper trenches with vertical walls in a wet-chemical etching process. Additionally, the electrical contacts at the platform are made from porous metal to increase the surface-to-volume ratio, to increase the possibility of a spontaneous electrical contact between the electrodes and nanowires.
Moosavi, Hoda S., Kröner, Michael, Frei, Maxi, Frick, Fabian, Kerzenmacher, Sven, Woias, Peter
Development of a TEM Compatible Nanowire Characterization Platform With Self-Forming Contacts
2018 IEEE Transactions on Semiconductor Manufacturing, Band: 31, Nummer: 1, Seite: 22–31
N. Wipf, K. Mavridis, S. Hin, K. Mitsakakis, M. Specht, S. Medves, B. Carman, P. Müller, J. Vontas
Development of multiplex TaqMan assays for the LabDisk – an automated diagnostic platform for malaria vectors
2018 7th MIM Pan African Malaria Conference - Dakar, 18.04.2018
Hoch K, Pothof F, Becker F, Paul O, Ruther P
Development, Modeling, Fabrication, and Characterization of a Magnetic, Micro-Spring-Suspended System for the Safe Electrical Interconnection of Neural Implants
2018 Micromachines-basel, Band: 9, Nummer: 9, Ergänzungsband: 424, Seiten: 1 - 19
K. Mitsakakis / V. D’Acremont, S. Hin, F. von Stetten, R. Zengerle
Diagnostic tools for tackling febrile illness and enhancing patient management
2018 Microelectron Eng, Band: 201, Seiten: 26 - 59
KurzfassungMost patients with acute infectious diseases develop fever, which is frequently a reason to visit health facilities in resource-limited settings. The symptomatic overlap between febrile diseases impedes their diagnosis on clinical grounds. Therefore, the World Health Organization promotes an integrated management of febrile illness. Along this line, we present an overview of endemic and epidemic etiologies of fever and state-of-the-art diagnostic tools used in the field. It becomes evident that there is an urgent need for the development of novel technologies to fulfill end-users’ requirements. This need can be met with Point-of-Care and near-patient diagnostic platforms, as well as e-Health clinical algorithms, which co-assess test results with key clinical elements and biosensors, assisting clinicians in patient triage and management, thus enhancing disease surveillance and outbreak alerts. This review gives an overview of diagnostic technologies featuring a platform based approach: (i) assay (nucleic acid amplification technologies are examined); (ii) cartridge (microfluidic technologies are presented); (iii) instrument (various detection technologies are discussed); and at the end proposes a way that such technologies can be interfaced with electronic clinical decision-making algorithms towards a broad and complete diagnostic ecosystem.
S. Hin, B. Lopez-Jimena, M.A. Bakheit, V. Klein, S. Stack, C. Fall, A.A. Sall, K. Enan, S. Frischmann, L. Gillies, M. Weidmann, S. Goethel, V. Rusu, O. Strohmeier, N. Paust, R. Zengerle, K. Mitsakakis
Differential diagnosis of fever in West- and East-Africa
2018 WHO Geneva Health Forum, 10. – 12.04.2018, Genf / Schweiz
C.H. Tsai, X. Wu, D.H. Kuan, S. Zimmermann, R. Zengerle, P. Koltay
Digital hydraulic drive for microfluidics and miniaturized cell culture devices based on shape memory alloy actuators
2018 J Micromech Microeng, Band: 28, Seite: 084001
KurzfassungIn order to culture and analyze individual living cells, microfluidic cell culture and manipulation of cells becomes an increasingly important topic. Such microfluidic systems allow for exploring the phenotypic differences between thousands of genetically identical cells or pharmacological tests in parallel, which is impossible to achieve by traditional macroscopic cell culture methods. Therefore, plenty of microfluidic devices have been developed for cell biological studies like cell culture, cell sorting, and cell lysis in the past. However, these devices are still limited by the external pressure sources which most of the time are large in size and have to be connected by fluidic tubing leading to complex and delicate systems. In order to provide a miniaturized, more robust actuation system a novel, compact and low power consumption Digital Hydraulic Drive (DHD) has been developed that is intended for use in portable and automated systems for microfluidic applications. The DHD consists of a shape memory alloy (SMA) actuator and a pneumatic cylinder. The switching time of the digital modes (pressure ON vs. OFF) can be adjusted from 1 second to minutes. Thus, the DHDs might have many applications for driving microfluidic devices. In this work different implementations of DHDs are presented and their performance is characterized by experiments. In particular, it will be shown that DHDs can be used for microfluidic large-scale integration (mLSI) valve control (256 valves in parallel) as well as potentially for droplet-based microfluidic systems. As further application example high-throughput mixing of cell cultures (96 wells in parallel) are demonstrated employing the DHD and a so called "functional lid" (FL) approach, to enable a miniaturized microbioreactor in a regular 96-well micro well plate.
Lausecker R, Bollgruen P, Gleißner U, Wallrabe U
Digital lithography based on renewable materials as a tool for environmentally benign microfabrication
2018 J Clean Prod, Band: 172, Seiten: 3092 - 3101
R. Lausecker, P. Bollgruen, U. Gleißner, U. Wallrabe
Digital lithography based, on renewable materials as a tool for environmentally benign microfabrication
2018 J Clean Prod, Band: 172, Seiten: 3092 - 3101
Dongyang C, Behrmann O, Hufert F, Dame G, Urban G
Direct DNA and RNA detection from large volumes of whole human blood
2018 Sci Rep-uk, Band: 8, Seite: 3410
KurzfassungPCR inhibitors in clinical specimens negatively affect the sensitivity of diagnostic PCR and RT-PCR or may even cause false-negative results. To overcome PCR inhibition, increase the sensitivity of the assays and simplify the detection protocols, simple methods based on quantitative nested real-time PCR and RT-PCR were developed to detect exogenous DNA and RNA directly from large volumes of whole human blood (WHB). Thermus thermophilus (Tth) polymerase is resistant to several common PCR inhibitors and exhibits reverse transcriptase activity in the presence of manganese ions. In combination with optimized concentrations of magnesium ions and manganese ions, Tth polymerase enabled efficient detection of DNA and RNA from large volumes of WHB treated with various anticoagulants. The applicability of these methods was further demonstrated by examining WHB specimens collected from different healthy individuals and those stored under a variety of conditions. The detection limit of these methods was determined by detecting exogenous DNA, RNA, and bacteria spiked in WHB. To the best of our knowledge, direct RNA detection from large volumes of WHB has not been reported. The results of the developed methods can be obtained within 4 hours, making them possible for rapid and accurate detection of disease-causing agents from WHB.

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Z. Shu, B. Gerdes, M. Fechtig, L. Riegger, R. Zengerle, P. Koltay
Direct Printing of Conductive Metal Lines from Molten Solder Jets via StarJet Technology on Thin, Flexible Polymer Substrates
2018 NIP & Digital Fabrication Conference, Printing for Fabrication 2018, Dresden, 23. – 27.09.2018
Z. Shu, B. Gerdes, M. Fechtig, L. Riegger, R. Zengerle, P. Koltay
Direct Printing of Conductive Metal Lines from Molten Solder Jets via StarJet Technology on Thin, Flexible Polymer Substrates
2018 NIP & Digital Fabrication Conference, Printing for Fabrication 2018 Society for Imaging Science and Technology, Band: 4, Seiten: 72 - 75
KurzfassungWe present the direct printing of thin (linewidth of 70 μm) conductive lines from molten solder on thin, flexible substrates. The lines are generated via the so-called StarJet technology that enables the printing of micro jets from molten metal. In this work, metal lines are printed for the first time on flexible substrates, possibly enabling applications in the field of printed electronics. The printed lines are evaluated regarding their mechanical and electrical properties. To the knowledge of the authors, this is the first time that direct printing of a functional metallization, requiring no further treatment, on a flexible polymer substrate was demonstrated. The lines exhibit a low ohmic resistance and can endure shear forces of up to 3.5 N on polyethylene terephthalate (PET) substrates.
Dongyang C, Yi Q, Shen C, Lan Y, Urban G, Du W
Direct enrichment of pathogens from physiological samples of high conductivity and viscosity using H-filter and positive dielectrophoresis
2018 Biomicrofluidics, Band: 12, Nummer: 1, Seite: 014109
KurzfassungThe full potential of microfluidic techniques as rapid and accurate methods for the detection of disease-causing agents and foodborne pathogens is critically limited by the complex sample preparation process, which commonly comprises the enrichment of bacterial cells to detectable levels. In this manuscript, we describe a microfluidic device which integrates H-filter desalination with positive dielectrophoresis (pDEP) for direct enrichment of bacterial cells from physiological samples of high conductivity and viscosity, such as cow's milk and whole human blood. The device contained a winding channel in which electrolytes in the samples continuously diffused into deionized (DI) water (desalination), while the bacterial cells remained in the samples. The length of the main channel was optimized by numerical simulation and experimentally evaluated by the diffusion of fluorescein into DI water. The effects of another three factors on H-filter desalination were also investigated, including (a) the flow rate ratio between the sample and DI water, (b) sample viscosity, and (c) non-Newtonian fluids. After H-filter desalination, the samples were withdrawn into the dielectrophoresis chamber in which the bacterial cells were captured by pDEP. The feasibility of the device was demonstrated by the direct capture of the bacterial cells in 1× PBS buffer, cow's milk, and whole human blood after H-filter desalination, with the capture efficiencies of 70.7%, 90.0%, and 80.2%, respectively. We believe that this simple method can be easily integrated into portable microfluidic diagnosis devices for rapid and accurate detection of disease-causing agents and foodborne pathogens.
B. Gerdes, R. Zengerle, P. Koltay, L. Riegger
Direct printing of miniscule aluminum alloy droplets and 3D structures by StarJet technology
2018 J Micromech Microeng, Band: 28, Seite: 074003
KurzfassungDrop-on demand printing of molten metal droplets could be used for prototyping of 3D objects as promising alternative to laser melting technologies. However, up to date only few printheads were investigated for this purpose using only a limited range of materials. The pneumatically actuated StarJet technology presented previously enables the direct and non-contact printing of molten metal microdroplets from metal melts at high temperatures. Printheads according to the StarJet technology utilize nozzle chips featuring a star-shaped orifice geometry that leads to a formation of the droplets inside the nozzle with high precision. In this paper we present a novel StarJet printhead for printing aluminum alloys featuring a hybrid design with a ceramic reservoir for the molten metal and an outer shell fabricated from stainless steel. The micro machined nozzle chip is made from silicon carbide (SiC). This printhead can be operated at up to 950 °C and is capable of printing high melting metals like aluminum (Al) alloys in standard laboratory conditions. In this work, an aluminum-silicon alloy that features 12 % silicon (AlSi12) is printed. The printhead, the nozzle and the peripheral actuation system have been optimized for stable generation of AlSi12 droplets with high monodispersity, low angular deviation and miniaturized droplet diameters. As main result, a stable drop-on-demand printing of droplets exhibiting diameters of ddroplet = 702 µm +/- 1 % was demonstrated at 5 Hz with a low angular deviation of 0.3°, when a nozzle chip with 500 µm orifice diameter was used. Further, AlSi12 droplets featuring ddroplet = 176 µm ± 7 % were printed when using a nozzle chip with an orifice diameter of 130 µm. Moreover, we present directly printed objects from molten aluminum alloy droplets such as high aspect ratio, free-standing walls (aspect ratio 12:1) and directly printed, flexible springs to demonstrate the principle of 3D printing with molten metal droplets.
Mohamad Ahmadi, Fabian Kuhn, Rotem Oshman
Distributed Approximate Maximum Matching in the CONGEST Model
2018 32th Int. Symp. on Distributed Computing (DISC), New Orleans, USA
KurzfassungWe study distributed algorithms for the maximum matching problem in the CONGEST model, where each message must be bounded in size. We give new deterministic upper bounds, and a new lower bound on the problem. We begin by giving a distributed algorithm that computes an exact maximum (unweighted) matching in bipartite graphs, in O(n log n) rounds. Next, we give a distributed algorithm that approximates the fractional weighted maximum matching problem in general graphs. In a graph with maximum degree at most Delta, the algorithm computes a (1-eps)-approximation for the problem in time O(log(Delta W)/eps^2), where W is a bound on the ratio between the largest and the smallest edge weight. Next, we show a slightly improved and generalized version of the deterministic rounding algorithm of Fischer [DISC '17]. Given a fractional weighted maximum matching solution of value f for a given graph G, we show that in time O((log^2(Delta)+log^*n)/eps), the fractional solution can be turned into an integer solution of value at least (1-eps)f for bipartite graphs and (1-\eps).f.(g-1)/g for general graphs, where g is the length of the shortest odd cycle of G. Together with the above fractional maximum matching algorithm, this implies a deterministic algorithm that computes a (1-eps).f.(g-1)/g-approximation for the weighted maximum matching problem in time O(log(Delta W)/eps^2 + (log^2(Delta)+log^* n)/eps). On the lower-bound front, we show that even for unweighted fractional maximum matching in bipartite graphs, computing an (1 - O(1/sqrt{n}))-approximate solution requires at least Omega(D+sqrt{n}) rounds in CONGEST (ignoring log factors). This lower bound requires the introduction of a new 2-party communication problem, for which we prove a tight lower bound.
C. Van Pham, B. Britton, T. Böhm, S. Holdcroft, S. Thiele
Doped, Defect-Enriched Carbon Nanotubes as an Efﬁcient Oxygen Reduction Catalyst for Anion Exchange Membrane Fuel Cells
2018 Adv Mater Interfaces, Seite: 1800184
KurzfassungBond polarization of doped atoms and carbon and lattice defects are con- sidered important aspects in the catalytic mechanisms of oxygen reduction reaction (ORR) on heteroatom-doped carbon catalysts. Previous work on metal-free catalysts has focused either on bond polarization or lattice defects. Here multi-heteroatom doped defect-enriched carbon nanotubes (MH-DCNTs) that combine both effects to enhance ORR activity are designed. Lattice defects in MH-DCNTs are enriched by unzipping and length-shortening of carbon nanotubes, and also by creating carbon vacancies via decomposition of doped F atoms. Electrochemical analysis using rotating disc electrode voltam- metry shows that the ORR kinetic current density of MH-DCNT increases with lattice-defect density, the latter of which is veriﬁed by Raman spectroscopy, while the onset potential increases with annealing temperatures. An optimized MH-DCNT ORR catalyst exhibits a half-wave potential of 0.81 V versus revers- ible hydrogen electrode and limiting current density of 5.0 mA cm −2 at an electrode rotation speed of 1600 rpm in 0.1 M KOH. Further, it is demonstrated that MH-DCNT, as a cathode catalyst layer in an anion exchange membrane fuel cell (AEMFC), delivers a peak power density of 250 mW cm −2 , which is ≈70% the performance of an AEMFC using a conventional Pt/C catalyst.
K. Tröndle
Drop-on-Demand Bioprinting Process for Single-Spheroid Deposition and Immobilization
2018 International Conference on Biofabrication, Würzburg, 28. – 31.10.2018
Tobias Paxian, Sven Reimer, Bernd Becker
Dynamic Polynomial Watchdog Encoding for Solving Weighted MaxSAT
2018 International Conference on Theory and Applications of Satisfiability Testing, Springer, Band: 10929, Seiten: 37 - 53
KurzfassungIn this paper we present a novel pseudo-Boolean (PB) constraint encoding for solving the weighted MaxSAT problem with iterative SAT-based methods based on the Polynomial Watchdog (PW) CNF encoding. The watchdog of the PW encoding indicates whether the bound of the PB constraint holds. In our approach, we lift this static watchdog concept to a dynamic one allowing an incremental convergence to the optimal result. Consequently, we formulate and implement a SAT-based algorithm for our new Dynamic Polynomial Watchdog (DPW) encoding which can be applied for solving the MaxSAT problem. Furthermore, we introduce three fundamental optimizations of the PW encoding also suited for the original version leading to significantly less encoding size. Our experimental results show that our encoding and algorithm is competitive with state-of-the-art encodings as utilized in QMaxSAT (2nd place in last MaxSAT Evaluation 2017). Our encoding dominates two of the QMaxSAT encodings, and at the same time is able to solve unique instances. We integrated our new encoding into QMaxSAT and adapt the heuristic to choose between the only remaining encoding of QMaxSAT and our approach. This combined version solves 19 (4%) more instances in overall 30\% less run time on the benchmark set of the MaxSAT Evaluation 2017. Compared to each encoding of QMaxSAT used in the evaluation, our encoding leads to an algorithm that is on average at least 2X faster.
Timotius IK, Canneva F, Minakaki G, Pasluosta C, Moceri S, Casadei N, Riess O, Winkler J, Klucken J, von Horsten S, Eskofier B
Dynamic footprints of alpha-synucleinopathic mice recorded by CatWalk gait analysis.
2018 Data in Brief, Band: 17, Seiten: 189 - 193
KurzfassungCharacterizing gait is important in the study of movement disorders, also in clinical mouse models. Gait data are therefore necessary for the development of gait analysis methods and the study of diseases. This article presents gait data of two α-synucleinopathic transgenic mouse models and their non-transgenic littermate, backcrossed into the C57BL/6N genetic background. The animal gait was recorded using CatWalk system, which provides the information for each run about the paw positions, paw print sizes, and paw intensities as a function of time or video frame. A total of 90 run data files are provided in this article.
Roth J, Koch M D, Rohrbach A
Dynamics of a Protein Chain Motor Driving Helical Bacteria under Stress
2018 Biophys J, Band: 114, Nummer: 8, Seiten: 1955 - 1969

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Maria Hügle, Simon Heller, Manuel Watter, Manuel Blum, Farrokh Manzouri, Matthias Dümpelmann, Andreas Schulze-Bonhage, Peter Woias, Joschka Boedecker
Early Seizure Detection with an Energy-Efficient Convolutional Neural Network on an Implantable Microcontroller
2018 International Joint Conference on Neural Networks
López-Vidrier J, Gutsch S, Blázquez O, Valenta J, Hiller D, Laube J, Blanco-Portals J, López-Conesa L, Estradé S, Peiró F, Garrido B, Hernández S, Zacharias M
Effect of Si3N4-Mediated Inversion Layer on the Electroluminescence Properties of Silicon Nanocrystal Superlattices
2018 Adv Electron Mater, Band: 4, Nummer: 1700666
Laessig, Torsten, May, Michael, Heisserer, Ulrich, Riedel, Werner, Bagusat, Frank, Werff, Harm van der, Hiermaier, Stefan
Effect of consolidation pressure on the impact behavior of UHMWPE composites
2018 Compos Part B-eng, Band: 147, Seiten: 47 - 55
KurzfassungFor the first time, the influence of the manufacturing process on the dynamic performance of ultra-high molecular weight polyethylene (UHMWPE, Dyneema® HB26) composites is investigated. The material is significantly influenced by the hot-pressing parameters temperature and pressure. The ballistic resistance and shock wave behavior was characterized for the UHMWPE composite consolidated with three different pressures. In the case of UHMWPE composites, higher consolidation pressures result in a better ballistic performance. The shock wave behavior converges to high-density polyethylene (HDPE). Based on these observations, an analytical approach is proposed describing the equation of state as a function of consolidation pressure.
M. Kokko, S. Epple, J. Gescher, S. Kerzenmacher
Effects of wastewater constituents and operational conditions on the composition and dynamics of anodic microbial communities in bioelectrochemical systems
2018 Bioresource Technology, Band: 258, Seiten: 376 - 389
KurzfassungOver the last decade, there has been an ever-growing interest in bioelectrochemical systems (BES) as a sustainable technology enabling simultaneous wastewater treatment and biological production of, e.g. electricity, hydrogen, and further commodities. A key component of any BES degrading organic matter is the anode where electric current is biologically generated from the oxidation of organic compounds. The performance of BES depends on the interactions of the anodic microbial communities. To optimize the operational parameters and process design of BES a better comprehension of the microbial community dynamics and interactions at the anode is required. This paper reviews the abundance of different microorganisms in anodic biofilms and discusses their roles and possible side reactions with respect to their implications on the performance of BES utilizing wastewaters. The most important operational parameters affecting anodic microbial communities grown with wastewaters are highlighted and guidelines for controlling the composition of microbial communities are given.
Szabados J, Kini Manjeshwar S, Breunig I, Buse K
Electro-optic tuning of potassium tantalate-niobate whispering gallery resonators
2018 Laser Resonators, Microresonators, and Beam Control XX, San Francisco, CA, United States Proceedings of SPIE, Band: 10518, Seite: 1051802
KurzfassungMost centrosymmetric materials exhibit a neglectable electro-optic response; the Pockels coefficients are zero, while the DC-Kerr coefficients are typically small. For a standard material such as silica they are on the order of 10−22 m2/V2 . 1 Thus, refractive index tuning is achieved by thermal or mechanical means. Potassium tantalateniobate (KTa1−xNbxO3 with 0 < x < 1, KTN) is a rare exception. It offers outstandingly high DC-Kerr coefficients in the 10−15 m2/V2 range.2 In this contribution, the first-ever KTN whispering gallery resonators (WGR) are demonstrated with quality factors Q > 107 and electro-optic eigenfrequency tuning of more than 100 GHz at λ = 1040 nm for moderate field strengths of 250 V/mm. These results potentially pave the way for applications such as electro-optically tunable Kerr frequency combs.
Boehler C, Kleber C, Oberueber F, Asplund M
Electroactive coatings as a strategy to improve the longevity of neuroelectronic devices.
2018 Gordon Research Conference on Neuroelectronic Interfaces, 25.-30.03.2018, Galveston, TX, USA
Matylitskaya V, Kasemann S, Urban G, Dincer C, Partel S
Electrochemical Characterization of Nanogap Interdigitated Electrode Arrays for Lab-on-a-Chip Applications
2018 J Electrochem Soc, Band: 165, Nummer: 3, Seiten: B127 - B134
KurzfassungIn this work we present recent results on electrochemical characterization of the fabricated nanogap interdigitated electrode arrays (nIDAs) for Lab-on-a-Chip applications (LoC). The advantages of the presented nIDAs and their potential for application in bioelectrochemistry were studied using different electrochemical methods. Chronoamperometry is applied to achieve reversible redox processes which lead to an amplification of the measured current compared to a single electrode configuration and as a result, an increase in signal-to-noise ratio. For the electrochemical characterization of the created nIDAs ferrocenemethanol (FcMeOH) and p-aminophenol (pAP) were selected as redox couples. An amplification factor above 160 compared to a single electrode configuration was obtained with FcMeOH for the nIDAs with 100 nm gap. An inverse correlation between gap size and amplification was proven. In addition, the formation of a polymer film during redox cycling could be verified to cause the lower amplification factor observed in pAP measurements. Furthermore, different electrode cleaning procedures were demonstrated by combination of O2 plasma and cyclic voltammetry. The nIDAs presented here offer many advantages including low-cost fabrication, high amplification and collection factors and thus are highly suitable for biosensor applications.

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Pfau J, Ganatra D, Weltin A, Urban G, Kieninger J, Stieglitz T
Electrochemical Stability of Thin-Film Platinum as Suitable Material for Neural Stimulation Electrodes
2018 BMT 2018, Aachen, Germany Biomed Eng-biomed Te, Band: 63, Ergänzungsband: 1, Seite: S121
Urban S, Weltin A, Flamm H, Kieninger J, Deschner BJ, Kraut M, Dittmeyer R, Urban G
Electrochemical multisensor system for monitoring hydrogen peroxide, hydrogen and oxygen in direct synthesis microreactors
2018 Sensor Actuat B-chem
KurzfassungWe present an electrochemical microsensor system for the monitoring of hydrogen peroxide, dissolved hydrogen and dissolved oxygen inside a direct synthesis microreactor. The setup allows the online, in situ measurement of high reactant concentrations by amperometric detection of all three reactants in aqueous solution using chronoamperometric protocols. Hydrogen peroxide is a key chemical for industrial oxidation applications, and its catalyzed direct synthesis is an attractive process route. For the first time, we integrated an electrochemical cell into a high pressure stainless steel microreactor environment (pressures up to 100  bar, pH of 3-4 and presence of bromide) by fabricating sensor plugs with 300  µm platinum microelectrodes encapsulated into a robust epoxy housing. The first microfabricated silver/silver bromide pseudo-reference electrode, integrated by electrodeposition, allowed to obtain a stable measurement potential directly from the electrolyte containing bromide. The investigation of platinum electrochemistry in the presence of bromide by cyclic voltammetry led to the development of chronoamperometric protocols for the stable, precise and reproducible measurement in this environment. Hydrogen peroxide was detected under reaction conditions showing linear behaviour up to 20  mM with high sensitivity of 55  μA  cm⁻²  mM⁻¹ and excellent stability by application of a diffusion limiting hydrogel layer to the electrode surface. This linear range surpasses most micro- and nanostructured platinum approaches. Oxygen and hydrogen were both measured at elevated pressures up to 70  bar and high dissolved concentrations up to 52  mM and 40  mM with measured sensitivities of 26  μA  cm⁻²  mM⁻¹ and 356  μA  cm⁻²  mM⁻¹, respectively. We have successfully shown the application of electrochemical sensors for online, in situ monitoring of analyte concentrations under conditions found in direct synthesis microreactors.
Vomero M, Castagnola E, Ordonez JS, Carli S, Zucchini E, Maggiolini E, Gueli C, Goshi N, Ciarpella F, Cea C, Fadiga L, Ricci D, Kassegne S, Stieglitz T
Electrocorticography Arrays: Incorporation of Silicon Carbide and Diamond-Like Carbon as Adhesion Promoters Improves In Vitro and In Vivo Stability of Thin-Film Glassy Carbon Electrocorticography Arrays
2018 Advanced Biosystems, Band: 2, Nummer: 1
KurzfassungThin-film neural devices are an appealing alternative to traditional implants, although their chronic stability remains matter of investigation. In this study, a chronically stable class of thin-film devices for electrocorticography is manufactured incorporating silicon carbide and diamond-like carbon as adhesion promoters between glassy carbon (GC) electrodes and polyimide and between GC and platinum traces. The devices are aged in three solutions—phosphate-buffered saline (PBS), 30 × 10−3 and 150 × 10−3m H2O2/PBS—and stressed using cyclic voltammetry (2500 cycles) and 20 million biphasic pulses. Electrochemical impedance spectroscopy (EIS) and image analysis are performed to detect eventual changes of the electrodes morphology. Results demonstrate that the devices are able to undergo chemically induced oxidative stress and electrical stimulation without failing but actually improving their electrical performance until a steady state is reached. Additionally, cell viability tests are carried out to verify the noncytotoxicity of the materials, before chronically implanting them into rat models. The behavior of the GC electrodes in vivo is monitored through EIS and sensorimotor evoked potential recordings which confirm that, with GC being activated, impedance lowers and quality of recorded signal improves. Histological analysis of the brain tissue is performed and shows no sign of severe immune reaction to the implant.

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Reichel Christian, Würfel Uli, Winkler Kristina, Schleiermacher Hans-Frieder, Kohlstädt Markus, Unmüssig Moritz, Messmer Christoph, Hermle Martin, Glunz Stefan
Electron-selective contacts via ultra-thin organic interface dipoles for silicon organic heterojunction solar cells
2018 Journal of Applied Physics, Band: 123, Nummer: 2, Seite: 024505
KurzfassungIn the last years, novel materials for the formation of electron-selective contacts on n-type crystalline silicon (c-Si) heterojunction solar cells were explored as an interfacial layer between the metal electrode and the c-Si wafer. Besides inorganic materials like transition metal oxides or alkali metal fluorides, also interfacial layers based on organic molecules with a permanent dipole moment are promising candidates to improve the contact properties. Here, the dipole effect plays an essential role in the modification of the interface and effective work function of the contact. The amino acids L-histidine, L-tryptophan, L-phenylalanine, glycine, and sarcosine, the nucleobase adenine, and the heterocycle 4-hydroxypyridine were investigated as dipole materials for an electronselective contact on the back of p- and n-type c-Si with a metal electrode based on aluminum (Al). Furthermore, the effect of an added fluorosurfactant on the resulting contact properties was examined. The performance of n-type c-Si solar cells with a boron diffusion on the front was significantly increased when L-histidine and/or the fluorosurfactant was applied as a full-area back surface field. This improvement was attributed to the modification of the interface and the effective work function of the contact by the dipole material which was corroborated by numerical device simulations. For these solar cells, conversion efficiencies of 17.5% were obtained with open-circuit voltages (Voc) of 625mV and fill factors of 76.3%, showing the potential of organic interface dipoles for silicon organic heterojunction solar cells due to their simple formation by solution processing and their low thermal budget requirements.
Keller M, Goeppert J, Manoli Y, Savelli G, Colonna J, Faucherand P, Collin L, Fréchette L
Embedded Thermal Energy Harvesting – Challenges & Opportunities
2018 Presentation, 24th International Workshop on Thermal Investigations of ICs and Systems (THERMINIC)
A Gola, L Pastewka
Embedded atom method potential for studying mechanical properties of binary Cu-Au alloys
2018 Model Simul Mater Sc, Band: 26, Seite: 055006
KurzfassungWe present an embedded atom method (EAM) potential for the binary Cu–Au system. The unary phases are described by two well-tested unary EAM potentials for Cu and Au. We fitted the interaction between Cu and Au to experimental properties of the binary intermetallic phases Cu3Au, CuAu and CuAu3. Particular attention has been paid to reproducing stacking fault energies in order to obtain a potential suitable for studying deformation in this binary system. The resulting energies, lattice constant, elastic properties and melting points are in good agreement with available experimental data. We use nested sampling to show that our potential reproduces the phase boundaries between intermetallic phases and the disordered face-centered cubic solid solution. We benchmark our potential against four popular Cu–Au EAM parameterizations and density-functional theory calculations.
S Palzer, V Sandfort, J Goldschmidt, J Woellenstein
Enhancement Techniques to improve Raman spectroscopy of gases
2018 Sensoren und Messsysteme - 19. ITG/GMA-Fachtagung, Nürnberg, Deutschland
KurzfassungThe reliable chemical analysis of gas mixtures is a challenging task that is often approached by employing optical technologies because of their high reliability, sensitivity, and selectivity as well as the possibility of contactless measurement. When monitoring single or a few components of industrial or natural processes, absorption spectroscopy methods are frequently used. However, this approach becomes tedious when many gas species have to be identified and quantified. In this scenario Raman spectroscopy may offer a viable alternative for multi-gas analysis. In particular, spontaneous Raman scattering offers the possibility to qualitatively and quantitatively detect most molecules with a single laser source. Large-scale use of the technique currently fails due to the little amount of Raman-scattered light, which is a result of the small Raman-scattering cross-section. To mitigate this disadvantage, a number of approaches are currently being researched with the goal to obtain larger scattering intensities. To this effect currently popular methods aim to increase the effective amount of light via the use of optical resonators or photonic hollow fibres. In this article, both approaches are presented and the results achieved in natural gas analysis and food chain management are presented.
Kaiser, A.
Estudios de género y producción del género por las neurociencias.
2018 In C. Mora, A. Kottow, M. Ceballos, V. Osses (Eds.), Investigación, Políticas y Programas de Género., Seiten: 37 - 50
R Pohle, T Pohl, C Pannek, K Tarantik, ML Bauersfeld, J Wöllenstein, S Raible, F Seiler
Evaluation of a Colorimetric Sensor System for Early Fire Detection
2018 Eurosensors 2018, Graz, Austria , Band: 2, Nummer: 13, Seite: 966
KurzfassungThe use of colorimetric reactions as a sensitive, selective and low-cost method for the detection of fire related gases is evaluated in this work. As the most relevant fire gas carbon monoxide CO is addressed in the first place. A rhodium-based metal-organic complex has been selected, which a colorimetric material sensitive for CO. For the optical readout a compact setup has been developed which provides the option for spectroscopy in transmission and attenuated total reflection in parallel. The detection of CO in concentrations relevant for fire detection has been demonstrated in synthetic gas mixtures as well as in real fire gas.
Bryant, K., Grossi, G., Kaiser, A. (accepted)
Feminist Interventions on the Sex/Gender Question in Broca’s Area.
2018 The Scholar & Feminist Online; published by the Barnard Center for research on women.
Eltermann F, Wilde J
Fertigungsgerechte Primerprozesse für das mediendichte Umspritzen großer mechatronischer Komponenten - Prozesstechnologieentwicklung und Zuverlässigkeit
2018 Abschlussbericht zum IGF-Vorhaben 18734 N (FVA-Nr. 746 I „PRIME“), FVA-Heft Nr. 1287, Herausgabedatum: 30.04.2018
Fiath R, Raducanu BC, Musa S, Andrei A, Lopez CM, Welkenhuysen M, Ruther P, Aarts A, Ulbert I
Fine-scale mapping of cortical laminar activity during sleep slow oscillations using high-density linear silicon probes
2018 J Neurosci Meth
Hörsch J, Schäfer M, Becker S, Schramm S, Greiner M
Flow tracing as a tool set for the analysis of networked large-scale renewable electricity systems
2018 Int J Elec Power, Band: 96, Seiten: 390 - 397
KurzfassungThe method of flow tracing follows the power flow from net-generating sources through the network to the net-consuming sinks, which allows to assign the usage of the underlying transmission infrastructure to the system participants. This article presents a reformulation that is applicable to arbitrary compositions of inflow appearing naturally in models of large-scale electricity systems with a high share of renewable power generation. We propose an application which allows to associate power flows on the grid to specific regions or generation technologies, and emphasizes the capability of this technique to disentangle the spatio-temporal patterns of physical imports and exports occurring in such systems. The analytical potential of this method is showcased for a scenario based on the IEEE 118 bus network.
Tranberg B, Schäfer M, Brown T, Hörsch J, Greiner M
Flow-based analysis of storage usage in a low-carbon European electricity scenario
2018 15th International Conference on the European Energy Market (EEM), 2018

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Tranberg B, Schwenk-Nebbe LJ, Schäfer M, Hörsch J, Greiner M
Flow-based nodal cost allocation in a heterogeneous highly renewable European electricity network
2018 Energy, Band: 150, Seiten: 122 - 133
KurzfassungFor a cost efficient design of a future renewable European electricity system, the placement of renewable generation capacity will seek to exploit locations with good resource quality, that is for instance onshore wind in countries bordering the North Sea and solar PV in South European countries. Regions with less favorable renewable generation conditions benefit from this remote capacity by importing the respective electricity as power flows through the transmission grid. The resulting intricate pattern of imports and exports represents a challenge for the analysis of system costs on the level of individual countries. Using a tracing technique, we introduce flow-based nodal levelized costs of electricity (LCOE) which allow to incorporate capital and operational costs associated with the usage of generation capacity located outside the respective country under consideration. This concept and a complementary allocation of transmission infrastructure costs is applied to a simplified model of an interconnected highly renewable European electricity system. We observe that cooperation between the European countries in a heterogeneous system layout does not only reduce the system-wide LCOE, but also the flow-based nodal LCOEs for every country individually.
Zappe H
Fluidic micro-imaging systems (Keynote talk).
2018 13th IEEE International Conference on Nano/Micro Engineered and Molecular Systems (NEMS 2018), Singapore
M. Lehnert, E. Kipf, F. Schlenker, N. Borst, R. Zengerle, F. von Stetten
Fluorescence signal-to-noise optimisation for real-time PCR using universal reporter oligonucleotides
2018 Anal Methods-uk
KurzfassungIn this study we optimised the fluorescence signal generation of contact quenched universal reporter oligonucleotides. These are used as secondary probes in real-time Mediator Probe PCR to detect the sequence-specific cleavage of label-free primary mediator probes. Since the fluorescence signal generation of a universal reporter is not influenced by the target DNA sequence, optimisation of the fluorescence signal-to-noise ratio will improve the performance of all Mediator Probe PCRs that are based on this type of universal reporter. To determine the critical factors influencing signal-to-noise optimisation, we systematically analysed four parameters. These parameters were type of fluorophore, type of quencher molecule, intramolecular orientation of both residuals, and the number of quencher labels. In total, more than 30 different fluorogenic universal reporter structures were analysed, covering the whole fluorescence spectrum from green to crimson. From our results, we deduced a novel set of guidelines for signal-to-noise optimisation in the design of contact quenched, fluorogenic universal reporter oligonucleotides. We confirmed these guidelines in a different thermocycler, and by designing a second set of universal reporters, which were used for multiplex real-time PCR quantification of acute lymphoblastic leukaemia marker sequences. This optimised biplex Mediator Probe PCR showed an improved performance under clinical conditions, with a 10 times higher resolution regarding the limit of quantification. In addition to Mediator Probe PCR, these guidelines may also prove useful in signal-to-noise optimisation of other fluorescence-based assays where contact quenched oligonucleotides or secondary reporter molecules are used.
L. Becherer, M. Bakheit, S. Frischmann, S. Stinco, N. Borst, R. Zengerle, F. von Stetten
Fluorogenic real-time detection of loop-mediated isothermal amplification by novel mediator displacement probes demonstrated for HIV-1 and HTLV-1
2018 International Biotech Innovation Days, 23 - 25 May 2018 / Senftenberg, Germany
Diaz-Maue L, Schwaerzle M, Ruther P, Luther S, Richter C
Follow the Light - From Low-Energy Defibrillation to Multi-Site Photostimulation
2018 40th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), Honolulu, HI, USA , Seiten: 4832 - 4835
KurzfassungOne major cause of death in the industrialized world is sudden cardiac death, which so far can be reliably treated only by applying strong electrical shocks. Developing improved methods, aiming at lowering shock intensity and associated side effects potentially has significant clinical implications. Thus, optogenetic stimulation using structured illumination has been introduced as a promising experimental tool to investigate mechanisms underlying multi-site pacing and to optimize potential low-energy approaches. Furthermore, an objective of this work is to strengthen the application of optogenetic tools for cardiac arrhythmia research, which in turn is expected to improve applicable technologies towards tissue-protective defibrillation.
Diaz-Maue L, Schwärzle M, Ruther P, Luther S, Richter C
Follow the light - from low-energy defibrillation to multi-site photostimulation
2018 EMBC 2018 Conference, Hawaii, USA
Herr S, Brasch V, Szabados J, Obrzud E, Jia Y, Lecomte S, Buse K, Breunig I, Herr T
Frequency comb up- and down-conversion in synchronously driven χ(2) optical microresonators
2018 Opt Lett, Band: 43, Seite: 5745
KurzfassungOptical frequency combs are key to optical precision measurements. While most frequency combs operate in the near-infrared (NIR) regime, many applications require combs at mid-infrared (MIR), visible (VIS), or even ultra-violet (UV) wavelengths. Frequency combs can be transferred to other wavelengths via nonlinear optical processes; however, this becomes exceedingly challenging for high-repetition-rate frequency combs. Here it is demonstrated that a synchronously driven high- microresonator with a second-order optical nonlinearity can efficiently convert high-repetition-rate NIR frequency combs to VIS, UV, and MIR wavelengths, providing new opportunities for microresonator and electro-optic combs in applications including molecular sensing, astronomy, and quantum optics
M. Schulz, N. Borst, M. Specht, S. Calabrese, F. von Stetten, R. Zengerle, N. Paust
From nasal swab to digital answer: unit operations for antibiotic resistance screening on a single cell level
2018 MicroTAS 2018, 11. -15. November 2018, Kaohsiung / Taiwan
B. Gerdes, M. Jehle, N. Lass, L. Riegger, A. Spribille, M. Linse, F. Clement, R. Zengerle, P. Koltay
Front side metallization of silicon solar cells by direct printing of molten metal
2018 Solar Energy Materials and Solar Cells, Band: 180, Seiten: 83 - 90
KurzfassungIn this work, a new approach for the front side metallization of silicon solar cells is presented. Molten solder (Sn96Ag3Cu) is directly printed in a non-contact manner on solar cell precursors via StarJet technology. The StarJet technology features a pneumatically driven, heatable printhead with a reservoir of molten metal and a star-shaped silicon nozzle chip. Using this printhead, a jet of molten metal with 55 μm ± 5 μm diameter is generated and used to apply busbars as well as contact fingers on prefabricated electroplated seed layers. After deposition via StarJet, printed fingers have a minimum width of 70 μm and a mean aspect ratio of 0.94. The printed metallization is evaluated optically and electrically. Aluminum back surface field silicon solar cells with front side electroplated NiAg seed layers and StarJet metallization (busbars and fingers) show efficiencies of up to 18.1% after degradation. Solder is about 30–40 times cheaper than silver and therefore may allow costefficient solar cell metallization. The StarJet metallization on electroplated NiAg seed layers is fully functional and requires no additional post-processing steps. Only 6 mg of Ag per cell are consumed for the seed layer. As a proof-of-principle, a module is demonstrated, which consists of four solar cells that are metallized via StarJet.
De Dorigo D, Moranz C, Graf H, Marx M, Wendler D, Shui B, Herbawi A, Kuhl M, Ruther P, Paul O, Manoli Y
Fully Immersible Subcortical Neural Probes with Modular Architecture and a Delta-Sigma ADC Integrated under each Electrode for Parallel Readout of 144 Recording Sites
2018 IEEE Journal Solid-State Circuits (JSSC), Band: 53, Nummer: 11, Seiten: 3111 - 3125
De Dorigo D, Manoli Y
Fully Integrated Active Neural Probes for Deep Brain Monitoring Applications
2018 IEEE Brain Initiative Workshop on Advanced NeuroTechnologies
Khatri B, Lappe K, Habedank M, Müller T, Megnin C, Hanemann T
Fused Deposition Modeling of ABS-Barium Titanate Composites: A Simple Route towards Tailored Dielectric Devices
2018 Materials, Band: 10, Nummer: 6, Seite: 666
KurzfassungA process for the development, characterization and correlation of composite materials for 3D printing is presented, alongside the processing of a polymer-ceramic functional composite using fused deposition modeling (FDM). The composite was developed using acrylonitrile butadiene styrene (ABS) as the matrix material filled with barium titanate (BT) micro-powder up to 35 vol % (74.2 wt %). The ABS-BT composites exhibited a shear thinning behavior with increasing ceramic content. The composite was 3D printed into structural and functional test samples using FDM by adapting and optimizing the print parameters. Structural characterization revealed increasingly brittle behavior at higher filler ratios, with the ultimate tensile strength falling from 25.5 MPa for pure ABS to 13.7 MPa for the ABS-35 vol % BT composite. Four-point flexural tests showed a similar decrease in flexural strength with increasing ceramic content. Functional characterization revealed an increase in the relative permittivity at 200 kHz from 3.08 for pure ABS to 11.5 for the composite with 35 vol % BT. These results were correlated with the Maxwell-Garnett and Jayasundere-Smith effective medium models. The process described in this work can be used for other 3D printing processes and provides a framework for the rapid prototyping of functional composites into functional parts with reliable properties. The ABS-BT composite shows promise as a functional dielectric material, with potential applications as capacitors and light-weight passive antennas.
Nötzel D, Eickhoff R, Hanemann T
Fused Filament Fabrication of Small Ceramic Components
2018 Materials, Band: 11, Seite: 1463
KurzfassungWith respect to rapid prototyping of ceramic components, there are known only a few processes (stereo lithography, binder jetting). In this work, a new process chain is described in detail, showing that ceramics can be printed in a very cost-efficient way. We developed a ceramic–polymer composite as filament material that can be printed on a low-cost fused filament fabrication (FFF) desktop printer, even with very small nozzle sizes enabling very small geometric feature sizes. The thermal post-processing, with debinding and sintering, is very close to the ceramic injection molding (CIM) process chain.

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K. Kraiczek, G. Rozing, R. Zengerle
G-Index: A New Metric to Describe Dynamic Refractive Index Effects in HPLC Absorbance Detection
2018 Talanta, Band: 187, Seiten: 200 - 206
KurzfassungHigh performance liquid chromatography (HPLC) with a solvent gradient and absorbance detection is one of the most widely used methods in analytical chemistry. The observed absorbance baseline is affected by the changes in the refractive index (RI) of the mobile phase. Near the limited of detection, this complicates peak quantitation. The general aspects of these RI-induced apparent absorbance effects are discussed. Two different detectors with fundamentally different optics and flow cell concepts, a variable-wavelength detector equipped with a conventional flow cell and a diode-array detector equipped with a liquid core waveguide flow cell, are compared with respect to their RI behavior. A simple method to separate static – partly unavoidable – RI effects from dynamic RI effects is presented. It is shown that the dynamic RI behavior of an absorbance detector can be well described using a single, relatively easy-to-determine metric called the G-index. The G-index is typically in the order of a few seconds and its sign depends on the optical flow cell concept.
L Scholz, A O Ortiz Perez, B Bierer, J Wöllenstein, S Palzer
Gas sensors for climate research
2018 Sensoren und Messsysteme - 19. ITG/GMA-Fachtagung, Nürnberg, Deutschland
Kurzfassungn climate research, the availability of datasets providing information on the spatial and temporal characteristics of green-house gases are of high relevance for the development of reliable climate simulations. However, current gas measurement technologies does not lead to data in the quality and the scales needed for multiple reasons. To contribute to the ongoing search for a suitable method, a novel NDIR-type measurement system is presented that can provide high quality data of carbon dioxide (CO2) concentrations under field conditions at a fast measurement rate. Because of its low power requirements and its robust, low-maintenance and low-cost design, it is particularly suitable for the use as a sensor node as part of large-scale in-situ gas sensor networks.
L Scholz, A O Ortiz Perez, B Bierer, J Wöllenstein, S Palzer
Gas sensors for climate research
2018 J. Sens. Sens. Syst, Band: 7, Seiten: 535 - 541
KurzfassungThe availability of datasets providing information on the spatial and temporal evolution of greenhouse gas concentrations is of high relevance for the development of reliable climate simulations. However, current gas detection technologies do not allow for obtaining high-quality data at intermediate spatial scales with high temporal resolution. In this regard the deployment of a wireless gas sensor network equipped with in situ gas analysers may be a suitable approach. Here we present a novel, non-dispersive infrared absorption spectroscopy (NDIR) device that can possibly act as a central building block of a sensor node to provide high-quality data of carbon dioxide (CO2) concentrations under field conditions at a high measurement rate. Employing a gas-based, photoacoustic detector we demonstrate that miniaturized, low-cost, and low-power consuming CO2 sensors may be built. The performance is equal to that of standard NDIR devices but at a much reduced optical path length. Because of the spectral properties of the photoacoustic detector, no cross-sensitivities to humidity exist.
C Pannek, K Tarantik, L Engel, T Vetter, J Wöllenstein
Gasochromic Detection of NO2 on the Example of the Food Additive E141 (ii)
2018 Eurosensors 2018, Graz, Austria , Band: 2, Nummer: 13, Seite: 721
KurzfassungWe present our investigation on the gasochromic reaction of E141 (ii) towards the toxic gas nitrogen dioxide (NO2). E141 (ii) is a chlorophyllin-based food additive, typically used as green coloring for nearly all kinds of sweets. In this presentation we show an alternative approach for using E141 (ii) as optical gas indicator. All solid samples are prepared by multi-layer screen printing on different substrates like paper and PE-foil. Gas measurements are performed using an UV/Vis spectrometer. The influence of the substrate and according layer thickness is shown.
J. M. Stosch, A. Heumüller, C. Niemöller, S. Bleul, M. Rothenberg-Thurley, J. Riba, N. Renz, K. Szarc vel Szic, D. Pfeifer, M. Follo, H. L. Pahl, S. Zimmermann, J. Duyster, J. Wehrle, M. Lübbert, K. H. Metzeler, R. Claus, H. Becker
Gene mutations and clonal architecture in myelodysplastic syndromes and changes upon progression to acute myeloid leukaemia and under treatment
2018 Brit J Haematol, Band: 182, Seiten: 830 - 842
KurzfassungKnowledge of the molecular and clonal characteristics in the myelodysplastic syndromes (MDS) and during progression to acute myeloid leukaemia (AML) is essential to understand the disease dynamics and optimize treatment. Sequencing serial bone marrow samples of eight patients, we observed that MDS featured a median of 3 mutations. Mutations in genes involved in RNA-splicing or epigenetic regulation were most frequent, and exclusively present in the major clone. Minor subclones were distinguishable in three patients. As the MDS progressed, a median of one mutation was gained, leading to clonal outgrowth. No AML developed genetically independent of a pre-existing clone. The gained mutation mostly affected genes encoding signalling proteins. Additional acquisition of genomic aberrations frequently occurred. Upon treatment, emergence of new clones could be observed. As confirmed by single-cell sequencing, multiple mutations in identical genes in different clones were present within individual patients. DNA-methylation profiling in patients without identification of novel mutations in AML revealed methylation changes in individual genes. In conclusion, our data complement previous observations on the mutational and clonal characteristics in MDS and at progression. Moreover, DNA-methylation changes may be associated with progression in single patients. Redundancy of mutated genes in different clones suggests fertile grounds promoting clonal selection or acquisition.
Vomero M, Zucchini E, Delfino E, Gueli C, Mondragon NC, Carli S, Fadiga L, Stieglitz T
Glassy Carbon Electrocorticography Electrodes on Ultra-Thin and Finger-Like Polyimide Substrate: Performance Evaluation Based on Different Electrode Diameters.
2018 Materials, Band: 11, Nummer: 12, Seite: 2486
KurzfassungGlassy carbon (GC) has high potential to serve as a biomaterial in neural applications because it is biocompatible, electrochemically inert and can be incorporated in polyimide-based implantable devices. Miniaturization and applicability of GC is, however, thought to be partially limited by its electrical conductivity. For this study, ultra-conformable polyimide-based electrocorticography (ECoG) devices with different-diameter GC electrodes were fabricated and tested in vitro and in rat models. For achieving conformability to the rat brain, polyimide was patterned in a finger-like shape and its thickness was set to 8 µm. To investigate different electrode sizes, each ECoG device was assigned electrodes with diameters of 50, 100, 200 and 300 µm. They were electrochemically characterized and subjected to 10 million biphasic pulses—for achieving a steady-state—and to X-ray photoelectron spectroscopy, for examining their elemental composition. The electrodes were then implanted epidurally to evaluate the ability of each diameter to detect neural activity. Results show that their performance at low frequencies (up to 300 Hz) depends on the distance from the signal source rather than on the electrode diameter, while at high frequencies (above 200 Hz) small electrodes have higher background noises than large ones, unless they are coated with poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS).
Vomero M, Ashouri D, Oliveira A, Eickenscheidt M, Stieglitz T
Graphitic Carbon Electrodes on Flexible Substrate for Neural Applications Entirely Fabricated Using Infrared Nanosecond Laser Technology.
2018 Sci Rep-uk, Band: 8, Nummer: 1, Seite: 14749
KurzfassungNeural interfaces for neuroscientific research are nowadays mainly manufactured using standard microsystems engineering technologies which are incompatible with the integration of carbon as electrode material. In this work, we investigate a new method to fabricate graphitic carbon electrode arrays on flexible substrates. The devices were manufactured using infrared nanosecond laser technology for both patterning all components and carbonizing the electrode sites. Two laser pulse repetition frequencies were used for carbonization with the aim of finding the optimum. Prototypes of the devices were evaluated in vitro in 30 mM hydrogen peroxide to mimic the post-surgery oxidative environment. The electrodes were subjected to 10 million biphasic pulses (39.5 μC/cm2) to measure their stability under electrical stress. Their biosensing capabilities were evaluated in different concentrations of dopamine in phosphate buffered saline solution. Raman spectroscopy and x-ray photoelectron spectroscopy analysis show that the atomic percentage of graphitic carbon in the manufactured electrodes reaches the remarkable value of 75%. Results prove that the infrared nanosecond laser yields activated graphite electrodes that are conductive, non-cytotoxic and electrochemically inert. Their comprehensive assessment indicates that our laser-induced carbon electrodes are suitable for future transfer into in vivo studies, including neural recordings, stimulation and neurotransmitters detection.
L. Becherer, M. Schulz, H. Kuhn, M. Bakheit, S. Frischmann, F. Zitz, N. Borst, R. Zengerle, F. von Stetten
HIV-1 and HTLV-1 multiplex detection by digital mediator displacement LAMP
2018 MicroTAS 2018, 11. -15. November 2018, Kaohsiung / Taiwan
Laufer, Bernhard, Krueger-Ziolek, Sabine, Moeller, Knut, Docherty, Paul David, Hoeflinger, Fabian, Reindl, Leonhard
Hierarchical Analysis of Thorax Models to Measure Tidal Volume
2018 Current Directions in Biomedical Engineering, Band: 4, Nummer: 1, Seiten: 429 - 432
KurzfassungMotion tracking of thorax kinematics can be used to determine respiration. However, determining a minimal sensor configuration from 64 candidate sensor locations is associated with high computational costs. Hence, a hierarchical optimization method was proposed to determine the optimal combination of sensors. The hierarchical method was assessed by its ability to quickly determine the sensor combination that will yield optimal modelled tidal volume compared to body plethysmograph measurements. This method was able to find the optimal sensor combinations, in approximately 2% of the estimated time required by an exhaustive search.

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Lehmann K, Yurchenko O, Melke J, Fischer A, Urban G
High electrocatalytic activity of metal-free and non-doped hierarchical carbon nanowalls towards oxygen reduction reaction
2018 Electrochim Acta
KurzfassungUnderstanding the influence of synthesis parameters on morphology and electrochemical properties of carbon nanostructure is necessary for the development of application-tailored materials. We report on the synthesis by plasma enhanced chemical vapor deposition, morphology and catalytic activity towards oxygen reduction reaction (ORR) of hierarchical carbon nanowalls (hCNW) at different deposition times. hCNW are an advancement of common CNW possessing an increased surface area while retaining the ideal mass transport characteristics of common CNW. The hCNW structure results from a synthesis using p-xylene as an aromatic precursor. hCNW are non-doped and metal-free with easily accessible graphitic edge sites at the top of the walls and numerous defects sites located within the porous side walls, which are ideal sites for adsorption and electron transfer. hCNW reveal a high amount of different electrochemically active sites that dominate the material character depending on the deposition time. The hCNW exhibit excellent catalytic activity towards ORR with very high ORR onset potential of 830 mV vs RHE in 0.1  mol L⁻¹ KOH solution and selectivity towards a two electron transfer mechanism. Thereby, the onset is higher than that of several nitrogen doped carbons and one of the highest for pure carbon electrodes. In contrast to other pure carbon materials with similar onsets, oxygen doping of hCNW before the experiments could be ruled out. As such, the results of this paper indicate the existence of inner sphere ORR on sp²-carbon. Additionally, the results emphasize the relevance of often overlooked material properties such as surface accessibility as well as electrical conductivity for ORR.
Klein E, Gossler C, Paul O, Ruther P
High-density mLED-based otpical cochlear implant with improved thermomechanical behavior
2018 Front Neurosci-switz, Band: 12, Seiten: 659 - 659
Ruther P
High-density neural probe arrays using CMOS and MEMS technologies
2018 Neuroelectronic Interfaces, Beyond Feasibility - Bridging the Gap in Neuroelectronic Interfaces,Gordon Research Conference, March 25-30, 2018, Galveston,TX, USA
C. Klose, L. Bohn, M. Klingele, M. Breitwieser, S. Vierrath
How engineering the PEM|CL interface influences the performance of PEMFCs
2018 69th Annual Meeting of the International Society of Electrochemistry (ISE), Bologna/Italy, 02. – 07.09.2018
Richter Armin, Benick Jan, Fell Andreas, Hermle Martin, Glunz Stefan
Impact of bulk impurity contamination on the performance of high-efficiency n -type silicon solar cells
2018 Prog Photovoltaics, Band: 24, Nummer: 10, Seite: 1319
KurzfassungThe experimental variation of wafer thickness and resistivity at device level combined with a comprehensive device simulation study allows the identification of dominating recombinationinduced power loss mechanisms in high‐efficiency n‐type silicon solar cells (A. Richter et al, Sol. Energy Mater. Sol. Cells 173, p. 96, 2017). Under the assumption of specific Shockley‐Read‐Hall (SRH) recombination parameters, impurity recombination within the silicon bulk was identified as one main source for efficiency losses particularly for solar cells made of high‐resistivity silicon. In this work, we extend that analysis approach focusing on the SRH recombination parameters in order to investigate whether certain properties of these recombination‐active impurities can be identified using this kind of simulation‐based analysis. Reported SRH recombination parameters of various common impurities (eg, Fe, Cr, or Ni) were considered. It was found that a dominating role of certain impurities as Cu, Au, Co, or Zn can be excluded. A general simulation study as a function of the fundamental SRH recombination parameters allowed us to reduce the possible SRH parameters significantly in particular of the capture cross‐section ratio of electrons and holes. These results demonstrate that our analysis approach, which combines an experimental variation of wafer thickness and resistivity with a comprehensive device simulation, can provide deep insights into the solar cells loss mechanisms. In particular, the conclusions regarding SRH recombination are of importance for solar cells made of n‐type silicon as there are no meta‐stable impurity states formed that would allow a direct identification of impurity recombination–related power loss as reported for p‐type Si.
Otte E, Ayub S, Paul O, Ruther P
Implantable Optrode Enabling Electrophysiology and Optogenetic Stimulation
2018 ICAN – International Conference for Advanced Neurotechnology, University of Michigan, Ann Arbor, USA, 7./8. May 2018
Mohsen Ghaffari, Fabian Kuhn, Yannic Maus, Juho Hirvonen
Improved Distributed Delta-Coloring
2018 ACM Symposium on Principles of Distributed Computing (PODC)
KurzfassungWe present a randomized distributed algorithm that computes a $\Delta$-coloring in any non-complete graph with maximum degree $\Delta \geq 4$ in $O(\log \Delta) + 2^{O(\sqrt{\log\log n})}$ rounds, as well as a randomized algorithm that computes a $\Delta$-coloring in $O((\log \log n)^2)$ rounds when $\Delta \in [3, O(1)]$. Both these algorithms improve on an $O(\log^3 n/\log \Delta)$-round algorithm of Panconesi and Srinivasan~[STOC'1993], which has remained the state of the art for the past 25 years. Moreover, the latter algorithm gets (exponentially) closer to an $\Omega(\log\log n)$ round lower bound of Brandt et al.~[STOC'16].
Pfau J, Leal Ordonez JA, Stieglitz T
In Situ Measurement of Stimulus Induced pH Changes Using Thin- Film Embedded IrOx pH Electrodes.
2018 EMBC 2018 „40th International Engineering in Medicine and Biology Conference of the IEEE Engin. in Medicine and Biology Society“ , 17.07.-21.07.18 in USA Hawaii, USA IEEE, Seiten: 5049 - 5052
KurzfassungThe high complexity of the biological response to implanted materials builds a serious barrier against implanted recording and stimulation electrode arrays to succeed in clini- cally relevant chronic studies. Some of the cell and molecular inte ractions and the ir contribution to inflammation and de vice failure are s till uncle ar. The inte rre late d me chanis ms le ading to tissue damage and electrode array failure during simultaneous faradaic, electrochemical reactions and biological response under electrical stimulation are not understood sufficiently. One variable, with which inflammatory and electrode surface processes can be analyzed and assessed, is the pH change in the immediate environment of the material-tissue interface. Here, the greatest challenges are in the biocompatibility and in-vivo long-term stability of selected sensor materials, the measure- ment of small transient pH oscillations and positioning of the sensor at a defined and nearest possible distance in the mi- crometer range, to the site of activity without the pH sensing being affected by the material-tissue interactions itself. This work represents the in-situ measurement of local and transient pH changes at a pulsed electrode with an embedded in-vivo compatible pH sensor and therein differentiating from current approaches of pH sensing during electrical stimulation.
Urban G, Dincer C, Weltin A, Prenzler N, Schmitt H, Warnecke A, Falk C, Lenarz T
In-vitro and in-vivo sensors for monitoring neuronal restauration
2018 BMT 2018, Aachen, Germany Biomed Eng-biomed Te, Band: 63, Ergänzungsband: 1, Seite: S141
Herr S, Buse K, Breunig I
Incoherently pumped lasing and self-pumped three-wave mixing in laser-active whispering-gallery resonators
2018 Laser Resonators, Microresonators, and Beam Control XX, San Francisco, CA, United States Proceedings of SPIE, Band: 10518, Seite: 105180U
KurzfassungWe report lasing at 1064 nm in an LED-pumped high-Q whispering-gallery resonator (WGR) made from Nd:YVO4. A single LED is sufficient to achieve quasi-cw operation. Furthermore, self-pumped three-wave-mixing is demonstrated in high-Q WGRs made from laser-active lithium niobate. When pumping the resonator with a free-running laser diode without any external frequency stabilization, self-frequency doubling of the 1.08-μm laser line into the green spectral region is observed. With the application of quasi-phase matching techniques, the nonlinear optical processes can be selected at will, which enables compact and versatile self-pumped frequency synthesizers. As a proof-of-principle experiment, self-pumped optical parametric oscillation is demonstrated in a radially poled WGR made from neodymium-doped lithium niobate.
Quirynen R, Gros S, Diehl M
Inexact Newton-Type Optimization with Iterated Sensitivities
2018 SIAM Journal on Optimization, Band: 28, Nummer: 1, Seiten: 74 - 95
Frederico Goncalves de Cerqueira Lima, Ulrich Mescheder, Gábor Katona, Harald Leiste, Emre Özel, Holger Reinecke, Müller C
Influence of Silicon Doping Type on the Adhesion of Seedless Electrodeposited Copper Layers
2018 Surf Coat Tech, Band: 349, Seiten: 208 - 216
KurzfassungThe influence of silicon doping on the adhesion of copper layers electroplated directly on (100) silicon without a seed layer was investigated in this work. The adhesion of Cu layers on Si(100) was derived from scratch tests where the critical loads and the types of failures of these layers on phosphorous- and boron-doped silicon were obtained. The maximum loads supported until complete layer removals were about twice as large for Cu layers electrodeposited on p-Si(100) than those deposited on n-Si(100). The Cu layers were also visually inspected using images taken with scanning electron microscopes, their topography was obtained by atomic force microscope measurements and crystal orientations by X-ray *Manuscript_Review Click here to view linked References 2 diffraction. Secondary neutral mass spectroscopy measurements and X-ray photoelectron spectroscopy were used to quantitatively determine the atomic Cu concentration at the surface of each sample. Both measurements have detected larger Cu concentrations at the p-Si(100) surface than at n-Si(100). These measurements were used to support a model previously presented by this group to explain the adhesion difference of Cu electroplated directly on p- or n-doped Si.
C. Klose, L. Bohn, M. Klingele, M. Breitwieser, S. Vierrath
Influence of the PEM|CL interface on performance and water management
2018 Gordon Research Conference, Bryant University, Douglas Pike in Smithfield, RI, US., 29.07. – 03.08.2018
KurzfassungGordon Research Conference, Bryant University, Douglas Pike in Smithfield, RI, US., 29.07. – 03.08.2018
Eiselt T, Preinfalk J, Bittkau K, Gomard G, Hanemann T, Lemmer U
Inkjet-printed internal light extraction layers for organic light emitting diodes
2018 Flexible and printed electronics, Band: 3, Seite: 015007
KurzfassungWe have developed inkjet-printed scattering layers for enhanced light extraction in organic light emitting diodes (OLEDs). These layers are based on scattering polymer/nanoparticle composites, which are prepared from a solvent-free process and used for the outcoupling of waveguide modes to free propagating modes, thus improving the device efficiencies. Two different monomers are examined and an inkjet-printing process is developed for each of them. We first analyze the inks’ rheological properties, followed by the optical and morphological properties of the resulting layers. Upon integration of these printed layers into an OLED stack, the device efficiencies are increased by up to 40 % with respect to an unpatterned reference device. Furthermore, we show that these internal light extraction layers improve the angular and spectral stability of the devices.
AO Perez, H Gao, X Lyu, J Wöllenstein, V Kallfaß, J Fonollosa, S Palzer
Inkjet-printed, functional heterolayers of ZnO@ CuO for stoma pouch monitoring
2018 Appl Nanosci, Band: 8, Nummer: 8, Seiten: 1907 - 1914
KurzfassungMany bowel cancer patients are in need of an artificial stoma as part of their surgical treatment, and associated post-surgical odours caused by leaking stoma pouches may lead to social isolation, which is why inconspicuous monitoring of this situation is important for affected persons. The integration of micro- and nanotechnology may offer low-cost, low-power consumption and small solutions to this challenge. To this end, we present an inkjet-printed, heterostructured gas sensor that has been built by incorporating nanosized p-type semiconducting CuO in a porous n-type ZnO matrix. The functional layer is fabricated using a combination of a colloidal suspension and sol–gel approach optimized for inkjet printing thus offering an industry-ready method for integration of nanomaterials in microelectromechanical systems (MEMS) structures. Using a thermal modulation scheme we enhance the information content and classify different events. We demonstrate that a simple MEMS device using a novel hetero-nanomaterial may be used to reliably identify situations where stoma pouch content escapes.
Savelli G, Colonna J, Faucherand P, Wendler D, Manoli Y, Keller M
Integrated Thermoelectric Sensors for Thermal Monitoring of Integrated Circuits
2018 Presentation, 24th International Workshop on Thermal Investigations of ICs and Systems (THERMINIC)
Rudmann L, Alt MT, Ashouri Vajari D, Stieglitz T
Integrated optoelectronic microprobes
2018 Curr Opin Neurobiol, Band: 50, Nummer: June, Seiten: 72 - 82
KurzfassungAbstract: Optogenetics opened not only new exciting opportunities to interrogate the nervous system but also requires adequate probes to facilitate these wishes. Therefore, a multidisciplinary effort is essential to match these technical opportunities with biological needs in order to establish a stable and functional material-tissue interface. This in turn can address an optical intervention of the genetically modified, light sensitive cells in the nervous system and recording of electrical signals from single cells and neuronal networks that result in behavioral changes. In this review, we present the state of the art of optoelectronic probes and assess advantages and challenges of the different design approaches. At first, we discuss mechanisms and processes at the material-tissue interface that influence the performance of optoelectronic probes in acute and chronic implantations. We classify optoelectronic probes by their property of delivering light to the tissue: by waveguides or by integrated light sources at the sites of intervention. Both approaches are discussed with respect to size, spatial resolution, opportunity to integrate electrodes for electrical recording and potential interactions with the target tissue. At last, we assess translational aspects of the state of the art. Long-term stability of probes and the opportunity to integrate them into fully implantable, wireless systems are a prerequisite for chronic applications and a transfer from fundamental neuroscientific studies into treatment options for diseases and clinical trials. Highlights: - Miniaturization technologies enable multichannel optoelectronic neural probes. - No external laser is needed when light sources are directly integrated on the probes. - Connectors to recording equipment still limit further miniaturization. - Wireless systems with integrated multiplexers and amplifiers can replace connectors. - Longevity of probes is mandatory for chronic implantation.
Kretschmer S, Jäger J, Ataman C, Zappe H
Integration and biocompatible packaging of multi- modal endoscopic imagers using 3D glass micro structuring
2018 Proceedings of SPIE, Band: 10545, Seite: 105450Q
Ashouri Vajari D, Vomero M, Erhardt JB, Sadr A, Ordonez JS, Coenen VA, Stieglitz T
Integrity Assessment of a Hybrid DBS Probe that Enables Neurotransmitter Detection Simultaneously to Electrical Stimulation and Recording.
2018 Micromachines, Band: 9, Nummer: 10, Seiten: 510 - 524
KurzfassungDeep brain stimulation (DBS) is a successful medical therapy for many treatment resistant neuropsychiatric disorders such as movement disorders; e.g., Parkinson’s disease, Tremor, and dystonia. Moreover, DBS is becoming more and more appealing for a rapidly growing number of patients with other neuropsychiatric diseases such as depression and obsessive compulsive disorder. In spite of the promising outcomes, the current clinical hardware used in DBS does not match the technological standards of other medical applications and as a result could possibly lead to side effects such as high energy consumption and others. By implementing more advanced DBS devices, in fact, many of these limitations could be overcome. For example, a higher channels count and smaller electrode sites could allow more focal and tailored stimulation. In addition, new materials, like carbon for example, could be incorporated into the probes to enable adaptive stimulation protocols by biosensing neurotransmitters in the brain. Updating the current clinical DBS technology adequately requires combining the most recent technological advances in the field of neural engineering. Here, a novel hybrid multimodal DBS probe with glassy carbon microelectrodes on a polyimide thin-film device assembled on a silicon rubber tubing is introduced. The glassy carbon interface enables neurotransmitter detection using fast scan cyclic voltammetry and electrophysiological recordings while simultaneously performing electrical stimulation. Additionally, the presented DBS technology shows no imaging artefacts in magnetic resonance imaging. Thus, we present a promising new tool that might lead to a better fundamental understanding of the underlying mechanism of DBS while simultaneously paving our way towards better treatments.
da Costa CA, Pasluosta CF, Eskofier B, da Silva DB, da Rosa Righi R
Internet of Health Things: Toward intelligent vital signs monitoring in hospital wards.
2018 Artif Intell Med
KurzfassungBackground Large amounts of patient data are routinely manually collected in hospitals by using standalone medical devices, including vital signs. Such data is sometimes stored in spreadsheets, not forming part of patients’ electronic health records, and is therefore difficult for caregivers to combine and analyze. One possible solution to overcome these limitations is the interconnection of medical devices via the Internet using a distributed platform, namely the Internet of Things. This approach allows data from different sources to be combined in order to better diagnose patient health status and identify possible anticipatory actions. Methods This work introduces the concept of the Internet of Health Things (IoHT), focusing on surveying the different approaches that could be applied to gather and combine data on vital signs in hospitals. Common heuristic approaches are considered, such as weighted early warning scoring systems, and the possibility of employing intelligent algorithms is analyzed. Results As a result, this article proposes possible directions for combining patient data in hospital wards to improve efficiency, allow the optimization of resources, and minimize patient health deterioration. Conclusion It is concluded that a patient-centered approach is critical, and that the IoHT paradigm will continue to provide more optimal solutions for patient management in hospital wards. Graphical abstract Download high-res image (133KB)Download full-size image
Chlouba T, Trojánek F, Laube J, Hiller D, Gutsch S, Zacharias M, Malý P
Interplay of bimolecurlar and Auger recombination in photoexcited carrier dynamics in silicon nanocrystal/silicon dioxide superlattices
2018 Sci Rep-uk, Band: 1703
Ayub S, Ruther P, Paul O, Kohl P, Zgierski-Johnston CM
Invasive Optical Pacing in Perfused, Optogenetically Modified Mouse Heart Using Stiff Multi-LED Optical Probes
2018 40th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), Honolulu, HI, USA , Seiten: 4836 - 4839
KurzfassungWe present the first invasive use of a stiff, multiLED optical probe for intramural optical stimulation of cardiac tissue. We demonstrate that optical pacing is possible with high spatial and temporal resolution in transgenic mice expressing channelrhodopsin-2. The technical implementation of this study builds on optical probes recently developed and tested ex vivo in cerebral tissue of mice. The probes comprise LEDs integrated on flexible substrates stiffened by silicon-based MEMS structures enabling the successful penetration into the cardiac tissue. The probe technology is extended to allow dual-sided illumination for directional tissue stimulation. Implantation trials affirm the ability to optically pace the isolated perfused heart at stimulation frequencies between 4Hz and 12Hz with experimentally determined emittance levels of 10mW mm-2Rapid activation of two distant LEDs could reliably be used to induce short runs of ventricular fibrillation, while simultaneous activation of all LEDs allowed termination of re-entrant rhythm disturbances (optical defibrillation). Thus, spatially-resolved intramural pacing and rhythm control of the isolated heart is possible using stiff, multi-LED optical probes.
C Pannek, K Tarantik, K Schmitt, J Wöllenstein
Investigation of Gasochromic Rhodium Complexes Towards Their Reactivity to CO and Integration into an Optical Gas Sensor for Fire Gas Detection
2018 Sensors-basel, Band: 18, Nummer: 7, Seite: 1994
KurzfassungThe detection of the toxic gas carbon monoxide (CO) in the low ppm range is required in different applications. We present a study of the reactivity of different gasochromic rhodium complexes towards the toxic gas carbon monoxide (CO). Therefore, variations of binuclear rhodium complexes with different ligands were prepared. They were characterized by FTIR spectroscopy, 1H NMR spectroscopy, and differential scanning calorimetry. All complexes are spectroscopically distinguishable and temperature stable up to at least 187 °C. The gasochromic behavior of all different compounds was tested. Therefore, the compounds were dissolved in toluene and exposed to 100 ppm CO for 10 min to investigate their gas sensitivity and reaction velocity. The changes in the transmission spectra were recorded by UV/vis spectroscopy. Furthermore, a significant influence of the solvent to the color dyes’ gasochromic reaction and behavior was observed. After characterization, one complex was transferred as sensing element into an optical gas sensor. Two different measurement principles (reflection- and waveguide-based) were built up and tested towards their capability as gasochromic CO sensors. Finally, different gas-dependent measurements were carried out.
Otte E, Ayub S, Paul O, Ruther P
LED-based Intracerebral Optrode for Simultaneous Optical Stimulation and Electrophysiological Recording
2018 IEEE MEMS Conf. 2018, Belfast, Ireland , Seiten: 384 - 387
P. Juelg, M. Specht, E. Kipf, M. Lehnert, C. Eckert, N. Paust, R. Zengerle, T. Hutzenlaub
LabDisk for fully automated quantification of two leukemia associated gene targets
2018 MicroTAS 2018, 11. -15. November 2018, Kaohsiung / Taiwan
Reiterer, A., Leidinger, M.
Laserscanner zur Lichtraummessung: Präzise messen, effizient auswerten
2018 EI - Der Eisenbahningenieur, Nummer: Mai 2018, Seiten: 44 - 47
Schautzgy J, Wilde J
Lebensdaueruntersuchungen an vibrationsbelasteten elektrischen Steckverbindungssystemen
2018 Workshop des DVM-Arbeitskreises Zuverlässigkeit mechatronischer und adaptronischer Systeme, München, Seiten: II-1 - II-18
Meinert T, Rohrbach A
Light-sheet microscopy with adaptive Bessel beams
2018 submitted
Fiath R, Hofer K T, Csikos V, Horvath D, Nanasi T, Toth K, Pothof F, Böhler C, Asplund M, Ruther P, Ulbert I
Long-term recording performance and biocompatibility of chronically implanted cylindrically-shaped, polymer-based neural interfaces
2018 Biomed Eng Online, Seiten: 301 - 315
Fiath R, Hofer KT, Csikos V, Horvath D, Nanasi T, Toth K, Pothof F, Bohler C, Asplund M, Ruther P, Ulbert I
Long-term recording performance and biocompatibility of chronically implanted cylindrically-shaped, polymer-based neural interfaces.
2018 Biomedizinische Technik/Biomedical Engineering
KurzfassungStereo-electroencephalography depth electrodes, regularly implanted into drug-resistant patients with focal epilepsy to localize the epileptic focus, have a low channel count (6-12 macro- or microelectrodes), limited spatial resolution (0.5-1 cm) and large contact area of the recording sites (~mm2). Thus, they are not suited for high-density local field potential and multiunit recordings. In this paper, we evaluated the long-term electrophysiological recording performance and histocompatibility of a neural interface consisting of 32 microelectrodes providing a physical shape similar to clinical devices. The cylindrically-shaped depth probes made of polyimide (PI) were chronically implanted for 13 weeks into the brain of rats, while cortical or thalamic activity (local field potentials, single-unit and multi-unit activity) was recorded regularly to monitor the temporal change of several features of the electrophysiological performance. To examine the tissue reaction around the probe, neuron-selective and astroglia-selective immunostaining methods were applied. Stable single-unit and multi-unit activity were recorded for several weeks with the implanted depth probes and a weak or moderate tissue reaction was found around the probe track. Our data on biocompatibility presented here and in vivo experiments in non-human primates provide a strong indication that this type of neural probe can be applied in stereo-electroencephalography recordings of up to 2 weeks in humans targeting the localization of epileptic foci providing an increased spatial resolution and the ability to monitor local field potentials and neuronal spiking activity.
Langenmair M, Martens J, Gierthmuehlen M, Plachta DTT, Stieglitz T
Low temperature approach for high density electrical feedthroughs for neural implants using maskless fabrication techniques.
2018 40th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), 18.- 21.07.2018, Oahu, Hawaii, USA IEEE, Seiten: 2933 - 2936
KurzfassungImplantable electronic packages for neural implants utilize reliable electrical feedthroughs that connect the inside of a sealed capsule to the components that are exposed to the surrounding body tissue. With the ongoing miniaturization of implants requiring ever higher integration densities of such feedthroughs new technologies have to be investigated. The presented work investigates the sealing of vertical feedthroughs in aluminum-oxide-substrates with gold stud-bumps. The technology enables integration densities of up to 1600/cm 2 while delivering suitable water leak rates for realistic implantation durations of miniaturized packages (feedthrough-count $>50$, package-volume $<2$ cm $^{3})$ of more than 50 years. All manufacturing steps require temperatures below $420 ^{\circ}\mathrm {C}$ and are suitable for maskless rapid prototyping.
Jörg Schube, Leonard Tutsch, Tobias Fellmeth, Martin Bivour, Frank Feldmann, Thibaud Hatt, Florian Maier, Roman Keding, Florian Clement, Stefan W Glunz
Low-Resistivity Screen-Printed Contacts on Indium Tin Oxide Layers for Silicon Solar Cells With Passivating Contacts
2018 IEEE J Photovolt
KurzfassungThe capability for contact formation on indium tin oxide layers of different low-temperature screen printing silver pastes after thermal curing and photonic sintering is evaluated in detail. The 80-nm-thick indium tin oxide layers used in this study are sputtered at three different oxygen gas flows and, consequently, differ by their electrical and optical properties. All pastes are analyzed by means of simultaneous thermogravimetry-differential scanning calorimetry. After printing and contact formation processing, the lateral resistivity of the metal contacts and their contact resistivity to the indium tin oxide layers are determined. Furthermore, the microstructure of the metal electrodes is investigated to gain a deeper understanding of the underlying contact formation mechanisms. Besides low-temperature curing at T curing,low = 180–220 °C, as conventionally applied to silicon heterojunction solar cells, photonic sintering and thermal curing at medium temperatures T curing,mid = 250–350 °C are utilized. The higher curing temperatures in the range of T curing,mid enhance the sintering and densification processes of the different pastes, and thereby, lateral resistivities of 2.4–3.5 μΩ⋅cm and contact resistivities of 1.0–2.5 mΩ⋅cm2 are achieved. The results indicate a promising industry-relevant non-firing-through metallization approach for, e.g., poly-silicon-based structures like tunnel oxide passivating contacts, which allow comparatively high temperatures for contact formation processing. With thermal curing at T curing,low and photonic sintering, both compatible with temperature-sensitive silicon heterojunction solar cells, lateral finger resistivities of 6.5–9.4 μΩ⋅cm and contact resistivities of 1.2–2.5 mΩ⋅cm2 are achieved. Thereby, photonic sintering has the potential of a significantly reduced process time from several minutes down to 1–4 ms.
Yuliya Butkova, Ralf Wimmer, Holger Hermanns
Markov Automata on Discount!
2018 19. International GI/ITG Conference on Measurement, Modelling and Evaluation of Computing Systems (MMB), Reinhard German et al., Band: 10740
KurzfassungMarkov automata (MA) are a rich modelling formalism for complex systems combining compositionality with probabilistic choices and continuous stochastic timing. Model checking algorithms for different classes of properties involving probabilities and rewards have been devised for MA, opening up a spectrum of applications in dependability engineering and artificial intelligence, reaching out into economy and finance. In the latter more general contexts, several quantities of considerable importance are based on the idea of discounting reward expectations, so that the near future is more important than the far future. This paper introduces the expected discounted reward value for MA and develops effective iterative algorithms to quantify it, based on value- as well as policy-iteration. To arrive there, we reduce the problem to the computation of expected discounted rewards and expected total rewards in Markov decision processes. This allows us to adapt well-known algorithms to the MA setting. Experimental results clearly show that our algorithms are efficient and scale to MA with hundred thousands of states.
M. Trotter, N. Borst, F. von Stetten
Mediator probes for electrochemical DNA detection: Universal electrode functionalization for specific detection of different targets
2018 9th Euro Biosensors & Bioelectronics Congress November 29-30, 2018 Dublin, Ireland
J. Kokert, T. Beckedahl, L. M. Reindl
Medlay: A Reconfigurable Micro-Power Management to Investigate Self-Powered Systems
2018 Sensors, Band: 18, Nummer: 1, Seite: 259
KurzfassungIn self-powered microsystems, a power management is essential to extract, transfer and regulate power from energy harvesting sources to loads such as sensors. The challenge is to consider all of the different structures and components available and build the optimal power management on a microscale. The purpose of this paper is to streamline the design process by creating a novel reconfigurable testbed called Medlay. First, we propose a uniform interface for management functions e.g., power conversion, energy storing and power routing. This interface results in a clear layout because power and status pins are strictly separated, and inputs and outputs have fixed positions. Medlay is the ready-to-use and open-hardware platform based on the interface. It consists of a base board and small modules incorporating e.g., dc-dc converters, power switches and supercapacitors. Measurements confirm that Medlay represents a system on one circuit board, as parasitic effects of the interconnections are negligible. The versatility regarding different setups on the testbed is determined to over 250,000 combinations by layout graph grammar. Lastly, we underline the applicability by recreating three state-of-the-art systems with the testbed. In conclusion, Medlay facilitates building and testing power management in a very compact, clear and extensible fashion.
S. Hin, M. Loskyll, V. Klein, M. Keller, O. Strohmeier, F. von Stetten, R. Zengerle, K. Mitsakakis
Membrane-based sample inlet for centrifugal microfluidic cartridges
2018 Microelectron Eng, Band: 187-188, Seiten: 78 - 83
KurzfassungCentrifugal microfluidics enables the rapid execution of complex blood sample analyses in a fully automated manner at the point of care. However, during blood sample addition, the cartridge is at rest and centrifugal forces are not present to allocate the sample in a controlled way. We present a versatile approach for the user-friendly, well-controlled and safe sample addition into a centrifugal microfluidic cartridge for use in serology. It features a commercial (plasma separation) membrane stacked into the inlet chamber of the cartridge. This combination of sample inlet and plasma separation in one structural unit brings the advantage of reducing footprint in highly integrated point-of-care testing. By using a pipette the user may add a blood sample (90 μL) to the membrane holding the liquid by capillary forces. Flowing across the membrane, cells separate from blood plasma. The blood plasma releases into the downstream structure upon centrifugation. The mean plasma recovery rate was 57.3 (± 4.7) % and mean plasma purity 99.5 (± 0.6) % from samples of varying hematocrit (36%–59%). Furthermore, the analyte C-reactive protein (CRP) did not significantly adsorb to the membrane. This was concluded, since CRP immunoassay results with plasma from spiked whole blood, obtained from membrane-based plasma separation and from plasma separation on a standard laboratory centrifuge, did not significantly differ. Thus, the suggested approach is promising for simultaneous application as sample inlet holding the sample by capillary forces and as a plasma separation module for centrifugal microfluidics. Potential future applications may include other sample matrices. The use with further blood transfer devices (capillary, directly from fingertip) seems possible, yet requiring further evaluation.
Durr, Nathanael, Sauer, Martin, Hiermaier, Stefan
Mesoscale investigation of dynamic fracture in quartzite and sandstone and homogenization to macroscale
2018 Int J Solids Struct, Band: 144-145, Seiten: 160 - 179
KurzfassungThe work presented here is part of the MEMIN (Multidisciplinary Experimental and Modeling Impact Research Network) project, which is devoted to the experimental and numerical investigation of the effects of meteorite impact on geological materials from laboratory scale to natural scale. In general, high velocity impacts on rock material causes fractures in the target that may lead to spallation of material near surfaces. While spallation effects are of great importance for laboratory scale craters, they are much less significant in natural craters. Therefore, they need to be taken into account when comparing natural craters with laboratory craters, particularly, when scaling laws that provide relationships between laboratory and natural craters shall be developed. This scale bridging requires realistic quantification of spallation effects, which can be done with numerical methods if appropriate material models exist. For this purpose, we investigate dynamic fracture in quartzite and sandstone. We present a new methodology to derive three dimensional macroscale material data from one-dimensional dynamic fracture experiments, namely Hopkinson-Bar experiments in the spallation configuration, using a new mesoscale simulation model. Simulations are conducted with the in-house hydrocode SOPHIA. Mesoscopic material parameters are identified from a parameter study such that simulated macroscopic failure quantities conform to experimentally measured data. The calibrated mesoscale model is then subjected to a set of multiaxial load cases in order to derive macroscopic yield and failure parameters using averaging techniques. The results can be directly used to calibrate macroscale material models for dynamic fracture and will support the predictability of laboratory craters and, in particular, of spallation effects.
Rehberger F, Eickenscheidt M, Stieglitz T
Micro-folded 3D neural electrodes fully integrated in polyimide.
2018 Engineering in Medicine and Biology Conference (EMBC) 2018. 17-21 July 2018 . Honolulu, Hawaii, United States IEEE, Seiten: 4587 - 4590
KurzfassungRecent neural interfaces are characterized by high functionality and good adaptation to the target tissue. Still, the underlying manufacturing process is mainly planar and so are the device and contact surface. Therefore, three-dimensional structures to contact neuronal tissue are desired to gain higher selectivity. In the present study, local bending structures integrated in flexible electrode arrays based on polyimide are investigated. The bending is achieved by the contraction of a second polyimide (Durimide) that is embedded into grooves with a width of a few micrometers. The angle of the bending can be controlled with a high accuracy from 3 to 20 degrees by changing the geometry of the grooves and the imidization temperature These bending structures can be combined to achieve any desired angle for specific applications.
Kutluk H, Bruch R, Meirich M, Partel S, Urban G, Dincer C
Microfluidic biosensor for the electrochemical on-site detection of microRNAs
2018 MicroTAS 2018, Kaohsiung, Taiwan
KurzfassungIn this work we present a novel approach for the electrochemical detection of miRNAs using a microfluidic platform. Herein, a sensitive, versatile and low-cost biosensor is combined with an enzyme-linked assay to detect miRNAs via hybridization in very low sample volumes (560 nl). The applicability of the system is successfully shown by measuring the miRNA hsa-miR-197 with a limit of detection (LOD) of 6.4 nM and an inter-assay coefficient of variation of below 10%. It is shown that the microfluidic biosensor is capable of measuring low miRNA concentrations with high selectivity against non-targeted miRNAs.
Kieninger J, Weltin A, Flamm H, Urban G
Microsensor systems for cell metabolism – from 2D culture to organ-on-chip
2018 Lab Chip
KurzfassungMicrosensor systems for cell metabolism are essential tools for investigation and standardization in cell cul- ture. Electrochemical and optical read-out schemes dominate, which enable the marker-free, continuous, online recording of transient effects and deliver information beyond microscopy and end-point tests. There has been much progress in microfluidics and microsensors, but the translation of both into standard cell culture procedures is still limited. Within this critical review, we discuss different cell culture formats ranging from standard culture vessels to dedicated microfluidic platforms. Key aspects are the appropriate supply of cells, mass transport of metabolites to the sensors and generation of stimuli. Microfluidics enable the transition from static to dynamic conditions in culture and measurement. We illustrate the parameters oxy- gen (respiration), pH (acidification), glucose and lactate (energy metabolism) as well as short-lived reactive species (ROS/RNS) from the perspective of microsensor integration in 2D and 3D cell culture. We discuss different sensor principles and types, along with their limitations, microfabrication technologies and mate- rials. The state-of-the-art of microsensor platforms for cell culture is discussed with respect to sensor per- formance, the number of parameters and timescale of application. That includes the advances from 2D culture to the increasingly important 3D approaches, with specific requirements for organotypic micro- tissues, spheroids and solid matrix cultures. We conclude on the current progress, potential, benefits and limitations of cell culture monitoring systems from monolayer culture to organ-on-chip systems.

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Jia Y, Hanka K, Breunig I, Zawilski K.T., Schunemann P.G., Buse K.
Mid-infrared whispering gallery resonators based on non-oxide nonlinear optical crystals
2018 Laser Resonators, Microresonators, and Beam Control XX, San Francisco, CA, United States Proceedings of SPIE, Band: 10518, Seite: 105180X
KurzfassungHigh-quality whispering gallery resonators (WGRs) made of AgGaSe2 and CdSiP2 bulk crystals are fabricated. With femtosecond laser matching and subsequent fine polishing, the intrinsic Q-factors of these resonators are approaching values of 106 to 107 . By adjusting the coupling condition, maximum coupling efficiencies of 60% and 30% for AgGaSe2 and CdSiP2 resonators could be obtained. In addition, thermal effects on the distortion of the mode spectra of these resonators are also investigated. The results in this work reveal great potentials of WGRs made of non-oxide crystals for mid infrared applications.
Bhat Kashekodi A, Meinert T, Michiels R, Rohrbach A
Miniature scanning light-sheet illumination implemented in a conventional microscope
2018 Biomed Opt Express, Band: 9, Nummer: 9, Seiten: 4263 - 4274

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Fell Andreas, Schön Jonas, Müller Matthias, Wöhrle Nico, Schubert Martin, Glunz Stefan
Modeling Edge Recombination in Silicon Solar Cells
2018 IEEE Journal of Photovoltaics, Seite: 1–7
Kirsch M, Böhm T, Joseph K, Asplund M, Hofmann UG, Thiele S, Stieglitz T, Haas CA
Molecular and structural characterization of probe-tissue interactions in the rat brain.
2018 Gordon Research Conference on Neuroelectronic Interfaces, 25.-30.03.2018, Galveston, TX, USA
B Weber, T Suhina, T Junge, L Pastewka, F Brouwer, D Bonn
Molecular probes reveal deviations from Amontons’ law in multi-asperity frictional contacts
2018 Nat Commun, Band: 9, Seite: 888
KurzfassungAmontons’ law defines the friction coefficient as the ratio between friction force and normal force, and assumes that both these forces depend linearly on the real contact area between the two sliding surfaces. However, experimental testing of frictional contact models has proven difficult, because few in situ experiments are able to resolve this real contact area. Here, we present a contact detection method with molecular-level sensitivity. We find that while the friction force is proportional to the real contact area, the real contact area does not increase linearly with normal force. Contact simulations show that this is due to both elastic interactions between asperities on the surface and contact plasticity of the asperities. We reproduce the contact area and fine details of the measured contact geometry by including plastic hardening into the simulations. These new insights will pave the way for a quantitative microscopic understanding of contact mechanics and tribology.
Fischer, Kai, Hiermaier, Stefan, Riedel, Werner, Haering, Ivo
Morphology dependent assessment of resilience for urban areas
2018 Sustainability, Band: 10, Seiten: 1 - 14
KurzfassungThe formation of new threats and the increasing complexity of urban built infrastructures underline the need for more robust and sustainable systems, which are able to cope with adverse events. Achieving sustainability requires the strengthening of resilience. Currently, a comprehensive approach for the quantification of resilience of urban infrastructure is missing. Within this paper, a new generalized mathematical framework is presented. A clear definition of terms and their interaction builds the basis of this resilience assessment scheme. Classical risk-based as well as additional components are aligned along the timeline before, during and after disruptive events, to quantify the susceptibility, the vulnerability and the response and recovery behavior of complex systems for multiple threat scenarios. The approach allows the evaluation of complete urban surroundings and enables a quantitative comparison with other development plans or cities. A comprehensive resilience framework should cover at least preparation, prevention, protection, response and recovery. The presented approach determines respective indicators and provides decision support, which enhancement measures are more effective. Hence, the framework quantifies for instance, if it is better to avoid a hazardous event or to tolerate an event with an increased robustness. An application example is given to assess different urban forms, i.e., morphologies, with consideration of multiple adverse events, like terrorist attacks or earthquakes, and multiple buildings. Each urban object includes a certain number of attributes, like the object use, the construction type, the time-dependent number of persons and the value, to derive different performance targets. The assessment results in the identification of weak spots with respect to single resilience indicators. Based on the generalized mathematical formulation and suitable combination of indicators, this approach can quantify the resilience of urban morphologies, independent of possible single threat types and threat locations.
Pasluosta C, Hannink J, Gassner H, Von Tscharner V, Winkler J, Klucken J, Eskofier BM
Motor output complexity in Parkinson's disease during quiet standing and walking: Analysis of short-term correlations using the entropic half-life.
2018 Hum Movement Sci, Band: 58, Seiten: 185 - 194
KurzfassungParkinson's disease (PD) is associated with alterations in motor outputs such as center of pressure (CoP) adjustments during quiet standing and foot kinematics during walking. Previous research suggests that the complexity of motor outputs reflects the number of control processes stabilizing a specific movement, providing a measure that is linked to the neurological control of the movement. The Entropic Half Life (EnHL) represents a new method for assessing motor output complexity. We hypothesized that there will be a lack of neuromuscular control pathways for PD patients, resulting in a decrease in motor output complexity. We computed the EnHL of CoP adjustments during quiet standing and foot kinematics during walking of 70 PD patients and 33 age-matched controls. Patients with PD showed longer EnHL values compared to controls, suggesting a tighter motor control. Excluding vision led to a decrease of EnHL of CoP in both groups. EnHL was correlated with spatio-temporal gait parameters. We compared EnHL with the pull test and the timed up-and-go test. No significant differences were present in the pull test, yet motor output complexity was correlated with the timed up-and-go test. The results suggest a reduced complexity in motor outputs of PD patients affecting distinct motor functions.
Kubon M, Hartmann H, Moschallski M, Burkhardt C, Link G, Werner S, Lavalle P, Urban G, Vrana N E, Stelzle M
Multimodal Chemosensor‐Based, Real‐Time Biomaterial/Cell Interface Monitoring
2018 Advanced Biosystems, Seite: 1700236
KurzfassungReal‐time monitoring of the cell/biomaterial interface for biomedical applications can significantly improve the assessment of biomaterials. However, currently there are no multiparametric real‐time monitoring systems for the ex vivo assessment of biomaterials. This study presents a method for monitoring of cell and tissue response to biomaterials based on microsensor read‐outs of pH, O2, and impedance. In vitro, the sensors are compatible with cells implants. For ex vivo measurements, either a biodegradable polymer poly(lactic‐co‐glycolic acid) or a protein‐repellent plasma polymer nanofilm is coated onto sensor arrays and placed on the chorioallantoic membrane of avian embryo ex ovo cultures. Signals related to dissolved oxygen, pH, and electrical impedance are continuously acquired for up to 90 h. Optical observation, immunohistochemical examination of CD45, and Haematoxylin and Eosin (H&E) staining show different unspecific immune responses. Tissue inflammation, capsule formation, and neovascularization are observed. These results correlate well with the type of coating material and the signal patterns acquired by the chemosensors. In addition, tissue death can be inferred from sensor signal patterns. This system is intended to enable continuous monitoring of biomaterials and is envisioned as a prescreening tool to provide real‐time monitoring of cell/biomaterial interface and also to reduce animal testing for biomaterial assessment purposes.
Rognini G, Petrini FM, Raspopovic S, Valle G, Granata G, Strauss I, Solca M, Bello-Ruiz J, Herbelin B, Mange R, D'Anna E, Di Iorio R, Di Pino G, Andreu D, Guiraud D, Stieglitz T, Rossini PM, Serino A, Micera S, Blanke O
Multisensory bionic limb to achieve prosthesis embodiment and reduce distorted phantom limb perceptions.
2018 J Neurol Neurosur Ps
Boehler C, Asplund M
Nanostructured Pt as a high performance coating for neural interfaces
2018 Micro Alliance Workshop 2018, October 4-5, 2018, Freiburg, Germany
Boehler C, Asplund M
Nanostructured platinum as a high performance coating for neural interfaces with excellent stability and biocompatibility.
2018 International Conference on Advanced Neurotechnologies (ICAN), May 6-8, 2018, Ann Arbor, MI, USA
M. Breitwieser, S. Vierrath
Neue Kompositmembranen und Mikrocharakterisierung: Die Gruppe „Elektrochemische Energiesysteme“ an IMTEK und Hahn-Schickard
2018 Brennstoffzellenallianz Duisburg, 26. - 27. Juni 2018
J. Schemberg, M. Specht, M. Karle
Neue Wege in der Krebsdiagnostik - Mikrofluidische Strategien für die Medizin 4.0
2018 GIT-Laborfachzeitschrift, Band: 4, Seite: 16
Gkogkidis CA, Bentler C, Wang X, Gierthmuehlen M, Scheiwe C, Schmitz HC, Haberstroh J, Stieglitz T Ball T
Neurophysiological Evaluation of a Customizable μECoG-based Wireless Brain Implant.
2018 2018 40th AnInternational Conference of the IEEE Engineering in Medicine and Biology Society (EMBC) , 18.-21.07.2018, Oahu, HI, USA IEEE, Seiten: 2953 - 2956
KurzfassungThe number of implantable bidirectional neural interfaces available for neuroscientific research applications is still limited, despite the rapidly increasing number of customized components. We previously reported on how to translate available components into ”ready-to-use” wireless implantable systems utilizing components off-the-shelf (COTS). The aim of the present study was to verify the viability of a micro-electrocorticographic (μECoG) device built by this approach. Functionality for both neural recording and stimulation was evaluated in an ovine animal model using acoustic stimuli and cortical electrical stimulation, respectively. We show that auditory evoked responses were reliably recorded in both time and frequency domain and present data that demonstrates the cortical electrical stimulation functionality. The successful recording of neuronal activity suggests that the device can compete with existing implantable systems as a neurotechnological research tool.
Unmüssig T, Daubinger P, Weltin A, Urban S, Urban G, Kieninger J
Non-enzymatic glucose sensing based on hierarchical platinum micro-/nanostructures
2018 J Electroanal Chem, Band: 816, Seiten: 215 - 222
KurzfassungNon-enzymatic glucose monitoring for biomedical applications asks for long-term stable and selective sensors at neutral pH. A hierarchical platinum micro-/nanostructured electrode along with a novel measurement scheme leads to increased sensitivity, selectivity and stability compared to state-of-the-art. The hierarchical electrode coating was applied by a scalable two-step process, which combined electrochemical deposition and colloidal synthesis to obtain a hierarchical structure with high surface roughness. This three-dimensional structure consists of a cauliflower-like platinum deposition, which is coated by a platinum nanowire network. Amperometric glucose measurements showed a 10,000-fold increase in sensitivity (473  μA  cm⁻²  mM⁻¹) compared to unmodified electrodes and linear behavior in the physiological range. The obtained sensitivities are among the highest values reported for non-enzymatic glucose sensors in neutral pH media. The hierarchical morphology provides a selectivity mechanism depending on the reaction kinetics, improving the selectivity for glucose in the presence of the interferent ascorbic acid 2,000-fold. Selectivity was further enhanced by low-frequency electrochemical impedance spectroscopy (EIS). Chronoamperometric protocols were developed to achieve long-term stability and overcome the loss of sensitivity due to electrode poisoning. Using chronoamperometric protocols for both the amperometry and the EIS measurements improved stability significantly. The presented results make hierarchical platinum micro-/nanostructured electrodes a promising candidate for continuous glucose monitoring.
Zanelli A, Horn G, Frison G, Diehl Moritz
Nonlinear Model Predictive Control of a Human-sized Quadrotor
2018 Proceedings of the European Control Conference (ECC)
H Gao, J Amann, X Lyu, S Palzer
Novel Method for Thermal Characterization of MEMS
2018 J Microelectromech S, Band: 99, Seiten: 1 - 8
KurzfassungThe use of thermal modulation techniques provides powerful tools to enhance and influence the selectivity and sensitivity of metal oxide based functional layers in gas sensing applications. However, when using micromachined, low-power consuming, so-called hotplate devices, the determination of the absolute temperature of the sensitive layer still presents a challenge. In this contribution, a novel method based on a phase transition in thermally sensitive materials is applied to determine the absolute temperature with high accuracy. The technique relies on depositing small, well-defined amounts of various materials with high spatial resolution using an inkjet printer and then establishing the relation between the heater's resistivity and the absolute temperature when the phase transition occurs. With this approach, the spatial distribution of the absolute temperature of microelectromechanical systems can be achieved. Due to the flexibility of inkjet printing, the presented method may be applied to a wide range of scenarios.
T Kling, D Vogler, L Pastewka, F Amann, P Blum
Numerical simulations and validation of contact mechanics in a granodiorite fracture
2018 Rock Mech Rock Eng, Band: 51, Nummer: 9, Seiten: 2805 - 2824
KurzfassungNumerous rock engineering applications require a reliable estimation of fracture permeabilities to predict fluid flow and transport processes. Since measurements of fracture properties at great depth are extremely elaborate, representative fracture geometries typically are obtained from outcrops or core drillings. Thus, physically valid numerical approaches are required to compute the actual fracture geometries under in situ stress conditions. Hence, the objective of this study is the validation of a fast Fourier transform (FFT)-based numerical approach for a circular granodiorite fracture considering stress-dependent normal closure. The numerical approach employs both purely elastic and elastic–plastic contact deformation models, which are based on high-resolution fracture scans and representative mechanical properties, which were measured in laboratory experiments. The numerical approaches are validated by comparing the simulated results with uniaxial laboratory tests. The normal stresses applied in the axial direction of the cylindrical specimen vary between 0.25 and 10 MPa. The simulations indicate the best performance for the elastic–plastic model, which fits well with experimentally derived normal closure data (root-mean-squared error=9 µm). The validity of the elastic–plastic model is emphasized by a more realistic reproduction of aperture distributions, local stresses and contact areas along the fracture. Although there are differences in simulated closure for the elastic and elastic–plastic models, only slight differences in the resulting aperture distributions are observed. In contrast to alternative interpenetration models or analytical models such as the Barton–Bandis models and the “exponential repulsion model”, the numerical simulations reproduce heterogeneous local closure as well as low contact areas (<2%) even at high normal stresses (10 MPa), which coincides with findings of former experimental studies. Additionally, a relative hardness value of 0.14 for granitic rocks, which defines the general resistance to non-elastic deformation of the contacts, is introduced and successfully applied for the elastic–plastic model.
Ayasli R, Wilde J
Nutzung AVT-bezogener Merkmale zur Absicherung elektronischer Bauteile gegen Fälschung
2018 DVS Berichte, Elektronische Baugruppen und Leiterplatten EBL 2018, Band: 340, Seiten: 319 - 323
de la Oliva N, Mueller M, Stieglitz T, Navarro X, Del Valle J
On the use of Parylene C polymer as substrate for peripheral nerve electrodes.
2018 Sci Rep-uk, Band: 8, Nummer: 1, Seiten: 5965 - 5965
Marzioch J, Kieninger J, Weltin A, Flamm H, Aravindalochanan K, Sandvik J A, Pettersen E O, Peng Q, Urban G
On-Chip Photodynamic Therapy – Monitoring Cell Metabolism by Electrochemical Microsensors
2018 Lab Chip
KurzfassungWe introduce a new system which combines metabolic monitoring by electrochemical microsensors with photodynamic therapy on-chip for the first time. Oxygen consumption of T-47D breast cancer cells was measured during therapy with protoporphyrin IX. We determined the efficacy of therapy and revealed recovery effects, which underlines the high relevance of continuous monitoring.
M Jaegle, HF Pernau, M Pfützner, M Benkendorf, X Li, M Bartel, S Drost, J Wöllenstein
On-Chip Temperature Compensation for Thermal Impedance Sensors
2018 Eurosensors 2018, Graz, Austria , Band: 2, Nummer: 13, Seite: 1053
KurzfassungElectrical impedance spectroscopy is a widespread characterization method for solids or fluids in industrial applications. We here report on its thermal equivalent, the “thermal impedance spectroscopy”, improved by using a temperature compensation method for temperature dependent thermal measurements using an on-chip reference resistor.
Grether E, Bruch R, Kutluk H, Moser I, Jobst G, Goymann W, Gahr M, Urban G, Dincer C
On-site hormone monitoring using an electrochemical microfluidic biosensor for lab-on-a-bird applications
2018 MicroTAS 2018, Kaohsiung, Taiwan
KurzfassungIn this work, we introduce a microfluidic electrochemical platform to measure hormone levels of birds on-site. Herein, a low-cost and easy-to-handle biosensor is combined with a single-step competitive enzyme linked immunoassay. It enables to work with very low sample volumes (less than 600 nanoliters) along with a short sample-to-result time (about one hour). The feasibility of the system for future lab-on-a-bird applications is successfully demonstrated by measuring different testosterone concentrations in whole blood samples of zebra finches, reproducibly.
V Sandfort, J Goldschmidt, j Wöllenstein, S Palzer
One quantum sensor for all gases: cavity-enhanced Raman spectroscopy for food-chain monitoring
2018 Quantum Sensing and Nano Electronics and Photonics XV, San Francisco, California, United States , Band: 10540, Seite: 105400Z
KurzfassungThe comprehensive monitoring of the food chain, i.e. from growth to consumer, without gaps is of outstanding importance to consumer health and the food industry alike. Yet, due to the lack of suitable sensing technologies at adequate costs, only selective, critical spots can currently be monitored. While the particular food to be monitored may take any shape or form during processing, gases are always present and their composition is uniquely suited to learn about the state of the system. In this contribution, a universal quantum sensor concept to identify and quantify the components of complex gas matrices is presented. The sensing approach is based on detecting Raman scattered photons from inside a gas sample filled optical cavity. Because of the typically small Raman scattering cross-sections on the order of 10-30 cm2 a Fabry-Perot cavity with a Finesse of about 2,000 is used to enhance the available laser power of an extended cavity diode laser running at 780 nm. The scattered light is funneled onto a spectrometer after Rayleigh scattered photons have been suppressed using a notch filter. To allow in-situ determination of arbitrary gas matrices, the sensor concept relies on the diffusion of ambient air into the cavity. The setup is currently able to simultaneously detect gases with Raman spectra up to 3000 cm-1, which includes important indicators for food packaging, including nitrogen, oxygen, and carbon dioxide.
Hanemann T, Honnef K
Optical and Thermomechanical Properties of Doped Polyfunctional Acrylate Copolymers
2018 Polymers-basel, Band: 10, Nummer: 337, Seiten: 1 - 14
KurzfassungThree different polyfunctional acrylate monomers—trimethylolpropantriacrylate (TMPTA), pentaerythritol triacrylate (PETA) and di(trimethylolpropane) tetraacrylate (DTTA)—have been used as comonomers in combination with a reactive resin consisting of poly(methylmethacrylate), dissolved in its monomer methylmethacrylate. Phenanthrene has been added to form a guest–host system. The level of phenanthrene present may be adjusted to tailor the refractive index in the system. Prior to curing, the shear rate and temperature-dependent viscosity as a function of the composition were measured. It could be demonstrated that, with respect to different shaping methods, a tailor-made flow behaviour can be adjusted. After thermally-induced polymerization, the resulting optical (refractive index, optical transmittance) and thermomechanical (glass transition behavior, Vickers hardness) properties were characterized. A significant refractive index increase—up to a value close to 1.56 (@589 nm)—under the retention of good optical transmittance was able to be obtained. In addition, the photopolymerization behaviour was investigated to overcome the undesirable oxygen inhibition effect during the light-induced radical polymerization of acrylates. The level of acrylate units in the copolymer can compensate for the plasticizing effect of the dopant phenanthrene, enabling higher concentrations of the dopant in the guest–host system and therefore larger refractive index values suitable for polymer waveguide fabrication.

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De Schutter J, Leuthold R, Diehl M
Optimal Control of a Rigid-Wing Rotary Kite System for Airborne Wind Energy
2018 Proceedings of the European Control Conference (ECC)
Beh H, Hiller D, Zacharias M
Optimization of ALD-ZnO Thin Films Toward Higher Conductivity
2018 Phys Status Solidi A, Band: 1700880
M. Gorostiaga, M.C. Wapler, U. Wallrabe
Optimizing piezoelectric receivers for acoustic power transfer applications.
2018 Smart Material Structures
Kilias A, Canales A, Froriep UP, Park S, Egert U, Anikeeva P
Optogenetic entrainment of neural oscillations with hybrid fiber probes.
2018 J Neural Eng, Band: 15, Nummer: 5, Seiten: 056006 - 056006
Kermani H, Rohrbach A
Orientation-control of two plasmonically-coupled nanoparticles in an optical trap
2018 Acs Photonics

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Boehler C, Asplund M
PEDOT as a high charge injection material for low-frequency stimulation.
2018 40th International Conference of the IEEE Engineering in Medicine and Biology Society, 17.-21.07.2018, Oahu, Hawaii, USA IEEE
KurzfassungAlternating current stimulation (ACS) provides a versatile tool for modulating brain activity and presents a promising strategy for the treatment of neurological disorders like Parkinson’s disease or epilepsy. Stimulation of neural tissue at low-frequency however poses new challenges on conventional electrode materials which support limited charge transfer in the desired frequency range, from less than 0.1 Hz to several tens of Hz. In our study we address this challenge by investigating the charge transfer properties of PEDOT/PSS coatings for low-frequency applications, focusing on the impact of the polymer bulk. PEDOT films of various thicknesses were exposed to low-frequency as well as DC stimulation in vitro and compared to Pt and IrOx electrodes as controls. The charge injection performance of the metallic substrates could be substantially improved already by a thin PEDOT coating. Additionally a linear dependency between charge injection and polymer thickness suggests that PEDOT coatings are promising as materials for future ACS applications.
Pasluosta C, Kiele P, Stieglitz T
Paradigms for restoration of somatosensory feedback via stimulation of the peripheral nervous system.
2018 Clin Neurophysiol, Band: 129, Nummer: 4, Seiten: 851 - 862
KurzfassungThe somatosensory system contributes substantially to the integration of multiple sensor modalities into perception. Tactile sensations, proprioception and even temperature perception are integrated to perceive embodiment of our limbs. Damage of somatosensory networks can severely affect the execution of daily life activities. Peripheral injuries are optimally corrected via direct interfacing of the peripheral nerves. Recent advances in implantable devices, stimulation paradigms, and biomimetic sensors enabled the restoration of natural sensations after amputation of the limb. The refinement of stimulation patterns to deliver natural feedback that can be interpreted intuitively such to prescind from long-learning sessions is crucial to function restoration. For this review, we collected state-of-the-art knowledge on the evolution of stimulation paradigms from single fiber stimulation to the eliciting of multisensory sensations. Data from the literature are structured into six sections: (a) physiology of the somatosensory system; (b) stimulation of single fibers; (c) restoral of multisensory percepts; (d) closure of the control loop in hand prostheses; (e) sensory restoration and the sense of embodiment, and (f) methodologies to assess stimulation outcomes. Full functional recovery demands further research on multisensory integration and brain plasticity, which will bring new paradigms for intuitive sensory feedback in the next generation of limb prostheses.
Vomero M, Zuchini E, Gueli C, Delfino E, Ashouri D, Carli S, Fadiga L, Stieglitz T
Performance Evaluation of Glassy Carbon Electrodes for Neural Applications Based on Different Diameters.
2018 Gordon Research Conference on Neuroelectronic Interfaces, 25.-30.03.2018, Galveston, TX, USA
Granata G, Di Iorio R, Romanello R, Iodice F, Raspopovic S, Petrini F, Strauss I, Valle G, Stieglitz T, Cvancara P, Andreu D, Divoux JL, Giraud D, Wauters L, Hiairrassary A, Jensen W, Micera S, Rossini PM
Phantom somatosensory evoked potentials following selective intraneural electrical stimulation in two amputees.
2018 Clin Neurophysiol, Band: 129, Nummer: 6, Seiten: 1117 - 1120
KurzfassungObjective The aim of the paper is to objectively demonstrate that amputees implanted with intraneural interfaces are truly able to feel a sensation in the phantom hand by recording “phantom” somatosensory evoked potentials from the corresponding brain areas. Methods We implanted four transverse intrafascicular multichannel electrodes, available with percutaneous connections to a multichannel electrical stimulator, in the median and ulnar nerves of two left trans-radial amputees. Two channels of the implants that were able to elicit sensations during intraneural nerve stimulation were chosen, in both patients, for recording somatosensory evoked potentials. Results We recorded reproducible evoked responses by stimulating the median and the ulnar nerves in both cases. Latencies were in accordance with the arrival of somatosensory information to the primary somatosensory cortex. Conclusion Our results provide evidence that sensations generated by intraneural stimulation are truly perceived by amputees and located in the phantom hand. Moreover, our results strongly suggest that sensations perceived in different parts of the phantom hand result in different evoked responses. Significance Somatosensory evoked potentials obtained by selective intraneural electrical stimulation in amputee patients are a useful tool to provide an objective demonstration of somatosensory feedback in new generation bidirectional prostheses.
S Knobelspies, B Bierer, A Daus, A Takabayashi, GA Salvatore, G Cantarella,, AO Perez, J Wöllenstein, S Palzer, G Tröster
Photo-Induced Room-Temperature Gas Sensing with a-IGZO Based Thin-Film Transistors Fabricated on Flexible Plastic Foil
2018 Sensors-basel, Band: 18, Nummer: 2, Seite: 358
KurzfassungWe present a gas sensitive thin-film transistor (TFT) based on an amorphous Indium–Gallium–Zinc–Oxide (a-IGZO) semiconductor as the sensing layer, which is fabricated on a free-standing flexible polyimide foil. The photo-induced sensor response to NO2 gas at room temperature and the cross-sensitivity to humidity are investigated. We combine the advantages of a transistor based sensor with flexible electronics technology to demonstrate the first flexible a-IGZO based gas sensitive TFT. Since flexible plastic substrates prohibit the use of high operating temperatures, the charge generation is promoted with the help of UV-light absorption, which ultimately triggers the reversible chemical reaction with the trace gas. Furthermore, the device fabrication process flow can be directly implemented in standard TFT technology, allowing for the parallel integration of the sensor and analog or logical circuits.
M El-Safoury, C Weber, K Schmitt, HF Pernau, B Willing, J Woellenstein
Photoacoustic gas detector for the monitoring of sulfur dioxide content in ship emissions
2018 Sensoren und Messsysteme - 19. ITG/GMA-Fachtagung, Nürnberg, Deutschland
KurzfassungShip emissions heavily pollute marine ecosystems and are extremely detrimental to the health of humans in harbour areas. From 2020 on, the International Maritime Organization (IMO) is imposing tighter limits on global sulphur emissions. Although shipping companies can continue using heavy fuel oils, they are then obligated by international maritime law to install gas scrubbers for the purification of the exhaust gas. In addition, special exhaust gas measuring technology must be installed subsequent to the gas scrubber to detect the actually emitted SO2. We present the development of a low-cost, resonant photoacoustic (PA) gas detector for the monitoring of SO2 in marine vessels. A UV LED at 285 nm is used as light source in combination with a microphone as acoustic detector. In first experiments, we used acetone gas as a substitution for the harmful SO2 for sensor characterization. The results of the experiments show that SO2 concentrations between 0 and 111 ppm should be detectable with 2 ppm accuracy.
Beh H, Hiller D, Salava J, Trojánek F, Zacharias M, Malý P, Valenta J
Photoluminescence Dynamics and Quantum Yield of Intrinsically Conductive ZnO from Atomic Layer Deposition
2018 J Lumin, Band: 201, Nummer: 85
Fine, C., Jordan-Young, B., Kaiser, A., & Rippon, G. (accepted, translated from “Plasticity, plasticity, plasticity … (2013)).
Plasticidad, plasticidad, plasticidad… y la rigidez del problema del sexo.
2018 The Scholar & Feminist Online; published by the Barnard Center for research on women
Zappe H
Polymer optics for tunable and printable optical systems (Invited talk)
2018 Advanced Fabrication Technologies for Micro/Nano Optics and Photonics XI at SPIE Photonics West, San Francisco, CA, USA
Janz P, Hauser P, Heining K, Nestel S, Kirsch M, Egert U, Haas CA
Position- and Time-Dependent Arc Expression Links Neuronal Activity to Synaptic Plasticity During Epileptogenesis.
2018 Front Cell Neurosci, Band: 12, Seiten: 244 - 244
Feißt M, Schätzle P, Wilde J
Power Chip Interconnections Based on TLP and Sintering of CTE- Matched Conductors
2018 10th International Conference on Integrated Power Electronics Systems (CIPS), Stuttgart, Seiten: 331 - 336
Schiffmacher A, Litzenberger L, Wilde J, Polezhaev V, Huesgen T
Power Electronic Assemblies on Printed Wiring Boards Mounted by Silver Sintering
2018 7th Electronics System-Integration Technology Conference (ESTC), Dresden
M. Frei, J. Martin, S. Kindler, G. Cristiano, R. Zengerle, S. Kerzenmacher
Power supply for electronic contact lenses: Abiotic glucose fuel cells vs. Mg/air batteries
2018 J Power Sources, Band: 401, Seiten: 403 - 414
KurzfassungElectronic contact lenses are a promising platform for medical sensors. With these devices a variety of vital signs and medical parameters can be monitored noninvasively and without the risk of foreign body response. However, one current limitation of this technology is the need for an external power supply, resulting in bulky, multi component devices. In this paper, we for the first time investigate and compare the application of abiotic glucose fuel cells and Mg/air batteries as alternative power supply technologies for electronic contact lenses. While abiotic glucose fuel cells harvest energy from metabolites present in tear fluid, Mg/air batteries provide electricity by the oxidation of a sacrificial anode. Considering the space available on standard contact lenses, our results indicate that approx. 40 μW and 2 μW can be generated by Mg/air batteries and glucose fuel cells for a period of at least 24 h, respectively. However, coating galvanic cells with the commonly used contact lens material pHEMA, results in drastically reduced performance, presumably due to hindered mass transport. Nevertheless, even under those circumstances a Mg/air battery can still provide about 7 μW for 24 h, which would already be sufficient for many electronic contact lens applications.
Kluge F, Hannink J, Pasluosta C, Klucken J, Gassner H, Gelse K, Eskofier BM, Krinner S
Pre-operative sensor-based gait parameters predict functional outcome after total knee arthroplasty.
2018 Gait Posture, Band: 66, Seiten: 194 - 200
KurzfassungBackground Despite the general success of total knee arthroplasty (TKA) regarding patient-reported outcome measures, studies investigating gait function have shown diverse functional outcomes. Mobile sensor-based systems have recently been employed for accurate clinical gait assessments, as they allow a better integration of gait analysis into clinical routines as compared to laboratory based systems. Research question In this study, we sought to examine whether an accurate assessment of gait function of knee osteoarthritis patients with respect to surgery outcome evaluation after TKA using a mobile sensor-based gait analysis system is possible. Methods A foot-worn sensor-based system was used to assess spatio-temporal gait parameters of 24 knee osteoarthritis patients one day before and one year after TKA, and in comparison to matched control participants. Patients were clustered into positive and negative responder groups using a heuristic approach regarding improvements in gait function. Machine learning was used to predict surgery outcome based on pre-operative gait parameters. Results Gait function differed significantly between controls and patients. Patient-reported outcome measures improved significantly after surgery, but no significant global gait parameter difference was observed between pre- and post-operative status. However, the responder groups could be correctly predicted with an accuracy of up to 89% using pre-operative gait parameters. Patients exhibiting high pre-operative gait function were more likely to experience a functional decrease after surgery. Important gait parameters for the discrimination were stride time and stride length. Significance The early identification of post-surgical functional outcomes of patients is of great importance to better inform patients pre-operatively regarding surgery success and to improve post-surgical management.
F. Lemke, M. Stürmer, U. Wallrabe, M.C. Wapler
Pre-stressed Piezo Bending-buckling Actuators for Adaptive Lenses
2018 ACTUATOR 2018, 16th Int. Conference on New Actuators, Bremen, Germany , Seiten: 450 - 453
Hofmann F, Schäfer M, Brown T, Hörsch J, Schramm S, Greiner M
Principal Flow Patterns across renewable electricity networks
Epl-europhys Lett, Band: 124, Seite: 18005, 2018
M. Frei, C. Köhler, L. Dietel, J. Martin, F. Wiedenmann, R. Zengerle, S. Kerzenmacher
Pulsed electro-deposition of highly porous Pt-alloys for the use in methanol, formic acid, and glucose fuel cells
2018 Chemelectrochem, Seiten: 1013 - 1023
KurzfassungWe demonstrate an electro-deposition process for the fabrication of highly porous PtCu-alloy anodes. In the fabrication process, Pt and different amounts of a second noble metal (Pd, Ru, Au) are repeatedly co-deposited with Cu from an aqueous electrolyte, followed by selective dealloying of Cu. This way, highly porous PtCu alloys with roughness factors ranging from 400 to 4000 can be obtained. In all cases both noble metal partners are present on the electrode surface, whereas the majority of copper is likely buried underneath. In addition, we can show that H-desorption and COstripping yield substantially different roughness factors, even when applied to PtCu anodes. Hence, when using or comparing results from different stripping methods a calibration is required. Compared to PtCu anodes, small additions of Ru (~3 at% Ru) lead to significantly enhanced catalytic activity for the electro-oxidation of formic acid and methanol, whereas Au-rich PtCu-Au alloys (~75 at% Au) exhibit significantly improved electro-catalytic activity for glucose oxidation. In some cases, large variations impede the identification of significant differences in electro-catalytic activity. To reduce process variability and to increase the specific surface area further optimization of the fabrication process is required. Similarly, the deposition of defined alloy compositions will require further investigation since the composition of electrolyte and deposited alloy do not directly correspond.
Jia Y, Winkler M, Cheng C, Chen F, Kirste L, Cimalla V, Zukauskaite A, Szabados J, Breunig I, Buse K
Pulsed laser deposition of ferroelectric potassium tantalate-niobate optical waveguiding thin films
2018 Opt Mater Express, Band: 8, Nummer: 3, Seiten: 541 - 548
KurzfassungWe present the epitaxial growth of ferroelectric potassium tantalate-niobate (KTN) thin films by pulsed laser deposition. As a result of the optimization of the deposition and the surface finishing processes, a c-axis oriented KTa₀.₅Nb₀.₅O₃ thin film with homogeneous polarization phase grown on KTaO₃ and an efficient KTa₀.₅Nb₀.₅O₃ waveguiding thin film grown on MgO are demonstrated. The highly improved crystalline and optical quality of KTN layers grown in this work reveal the great potential of such films for integrated nonlinear optics.
Rauer Michael, Schmiga Christian, Glatthaar Markus, Glunz Stefan
Quantitative theoretical and experimental analysis of alloying from screen-printed aluminum pastes on silicon surfaces
2018 Solar Energy Materials and Solar Cells, Band: 176, Seite: 295–301
KurzfassungIn this study, we present detailed theoretical and experimental investigations on full-area alloying from screenprinted aluminum pastes on silicon surfaces for solar cell applications. We introduce a simple analytical model for the description of the alloying process derived from existing models for evaporated Al layers, which we adapt to printed Al pastes. Thereby, we particularly account for the recrystallization of Si within the paste particles, which we refer to as parasitic Si recrystallization. Applying our model, we demonstrate good accordance of calculated with measured eutectic layer thicknesses. We show that the model can be versatilely used to investigate screen-printed Al-alloyed contacts in detail: We demonstrate that the latent heat of the Al paste significantly influences the alloying process. Thus, the effective peak temperature of the alloying process can be several 100 °C below the set peak temperature of the firing furnace. By combining calculations of the effective peak temperature with measurements of the Al doping concentration, we determine a parameterization of the solid solubility of Al in Si down to the eutectic temperature of 577 °C. Our investigations therefore provide improved understanding of alloying from printed Al pastes and enable the specific optimization of Al-alloyed contacts.
Wolf R, Jia Y, Bonaus S, Werner C, Herr S, Breunig I, Buse K, Zappe H
Quasi-phase-matched nonlinear optical frequency conversion in on-chip whispering galleries
2018 Optica, Band: 5, Seite: 872
KurzfassungChip-integrated whispering-gallery resonators (WGRs) enable compact and wavelength-agile nonlinear optical frequency synthesizers. So far, the most flexible phase-matching technique, i.e., quasi-phase matching, has not been applied in this configuration. The reason is the lack of suitable thin films with alternating crystal structure on a low-refractive-index substrate. Here, we demonstrate an innovative method of realizing thin film substrates suitable for quasi-phase matching by field-assisted domain engineering of lithium niobate, and subsequent direct bonding and polishing. We are able to fabricate high- on-chip WGRs with these substrates by using standard semiconductor manufacturing techniques. The -factors of the resonators are up to one million, which allows us to demonstrate quasi-phase-matched second-harmonic generation in on-chip WGRs for the first time, to the best of our knowledge. The normalized conversion efficiency is 9×10−4 mW−1. This method can also be transferred to other material systems.
Herr S, Werner C, Buse K, Breunig I
Quasi-phase-matched self-pumped optical parametric oscillation in a micro-resonator
2018 Opt Express, Band: 26, Nummer: 8, Seiten: 10813 - 10819
KurzfassungLasing and self-pumped optical parametric oscillation (self-OPO) are achieved in a high-Q whispering-gallery-mode micro-resonator, made of neodymium-doped lithium niobate. A laser process providing 5 mW output power at 1.08 μm wavelength is sufficient to pump a self-OPO process within the same high-Q cavity. At 6 mW lasing output power, the sum of signal and idler output powers exceeds 1.2 mW. The wavelength of the generated light ranges from 1.5 to 3.8 μm. Phase matching is provided by a radial quasi-phase-matching structure, which is generated by a current-controlled calligraphic poling technique. To the best of our knowledge, this is the first demonstration of a quasi-phase-matched self-pumped nonlinear optical process in a micro-resonator, as well as the first self-OPO in a micro-resonator. The concept bears the potential for a highly integrated and wavelength-tunable coherent light source at low cost.
B Bierer, H-J Nägele, A Ortiz Perez, J Wöllenstein, Ph Kress, A Lemmer, S Palzer
Real‐Time Gas Quality Data for On‐Demand Production of Biogas
2018 Chemical Engineering Technology, Band: 41, Nummer: 4, Seiten: 696 - 701
KurzfassungThe flexible production of biogas makes it a promising candidate to become the first renewable, on‐demand energy source. One appealing possibility to achieve an on‐demand supply of methane is to adjust the output of the biogas plant itself. As a consequence, the biological process will be partially overloaded and might fail. Hence, a prerequisite to avoid cost‐intensive failure is a fast, reliable, and cost‐efficient analytical technology for quickly determining the biogas quality. A low‐cost, robust, in‐situ online measurement system for the real‐time determination of carbon dioxide and methane concentrations is presented. The approach makes use of photoacoustic detectors, allowing for the development of gas sensors with reduced size that do not show cross‐sensitivities towards water vapor. The system's readings may be used as input for a novel type of control system that enables an active, demand‐driven control of actuators, such as feeding machinery or mixers.
B Bierer, HJ Nägele, AO Perez, J Wöllenstein, P Kress, A Lemmer, S Palzer
Real‐Time Gas Quality Data for On‐Demand Production of Biogas
2018 Chem Eng Technol, Band: 41, Nummer: 4, Seiten: 696 - 701
KurzfassungThe flexible production of biogas makes it a promising candidate to become the first renewable, on‐demand energy source. One appealing possibility to achieve an on‐demand supply of methane is to adjust the output of the biogas plant itself. As a consequence, the biological process will be partially overloaded and might fail. Hence, a prerequisite to avoid cost‐intensive failure is a fast, reliable, and cost‐efficient analytical technology for quickly determining the biogas quality. A low‐cost, robust, in‐situ online measurement system for the real‐time determination of carbon dioxide and methane concentrations is presented. The approach makes use of photoacoustic detectors, allowing for the development of gas sensors with reduced size that do not show cross‐sensitivities towards water vapor. The system's readings may be used as input for a novel type of control system that enables an active, demand‐driven control of actuators, such as feeding machinery or mixers.
C Weber, J Kapp, K Schmitt, HF Pernau, J Wöllenstein
Resonant Photoacoustic Detection of NO2 with an LED Based Sensor
2018 Eurosensors 2018, Graz, Austria , Band: 2, Nummer: 13, Seite: 1036
KurzfassungIn times of steadily increasing air pollution especially in urban areas, the monitoring of nitrogen dioxide (NO 2) has gained in importance and with it the search for compact, low-cost sensors. We present a novel approach to measure NO 2 in sub-ppm concentrations with a photoacoustic sensor utilizing a T-shaped resonance cell. An inexpensive single LED with a peak wavelength of 410 nm was used as radiation source and the acoustic detection was done with a commercial MEMS microphone. For optimal coupling of the divergent LED light into the cell, the T-shaped resonator was developed and fabricated with rapid prototyping methods. The resonator shows a acoustic Q-factor> 10 while having nearly no zero gas signal.
M El-Safoury, M Dufner, C Weber, K Schmitt, HF Pernau, B Willing, J Wöllenstein
Resonant Photoacoustic Gas Monitoring of Combustion Emissions
2018 Eurosensors 2018, Graz, Austria , Band: 2, Nummer: 13, Seite: 962
KurzfassungSince the entrance into the industrial era and the increasing demand for energy due to global economic growth and development, the amount of energy-related emissions have continuously grown every year to significantly high levels. Greenhouse gases like carbon dioxide, nitrous oxide or methane cause an increase in the earth’s temperature. Toxic gases like nitrous oxides, Sulphur dioxide and carbon monoxide are extremely detrimental to the health of all living beings. Over the past few years, global organizations are imposing tighter limits by international laws for flue-gas emissions from fossil-fuel combustion. Emission-limiting techniques like filter and scrubber systems have to be installed for waste gas treatment in the exhaust gas streams. In addition, exhaust gas measuring technologies detect the actual emission values of the respective target gases. We present the development of a low-cost and highly sensitive photoacoustic gas detector for the monitoring of emitted combustion gases. First tests were carried out with the toxic Sulphur dioxide (SO 2) in secure lab conditions, where a sensitivity below 1 part per million (ppm) was achieved during continuous flow of the gas.
Wolf R, Breunig I, Zappe H, Buse K
Scattering-loss reduction of ridge waveguides by sidewall polishing
2018 Opt Express, Band: 26, Seite: 19815
KurzfassungRidge waveguides provide a large refractive index contrast and thus strong mode confinement, making them highly attractive for building compact photonic integrated circuits. However, ridge waveguides suffer from scattering losses. We demonstrate scattering-loss reduction of ridge waveguides made of lithium-niobate-on-insulator (LNOI) substrates by more than one order of magnitude. This is achieved by gently polishing of the ridge’s sidewalls and simultaneous protection of the top surfaces by a metal layer. Whispering-gallery-resonator loss measurements reveal ultra-low losses down to 0.04 dB/cm of the processed waveguides. Our approach pushes ridge waveguides further towards their fundamental absorption-loss limit, enabling highly efficient integrated devices.
Kieninger J, Tamari Y, Enderle B, Jobst G, Sandvik JA, Pettersen EO, Urban G
Sensor Access to the Cellular Microenvironment Using the Sensing Cell Culture Flask
2018 Biosensors, Band: 8, Nummer: 2, Seite: 44
KurzfassungThe Sensing Cell Culture Flask (SCCF) is a cell culture monitoring system accessing the cellular microenvironment in 2D cell culture using electrochemical microsensors. The system is based on microfabricated sensor chips embedded in standard cell culture flasks. Ideally, the sensor chips could be equipped with any electrochemical sensor. Its transparency allows optical inspection of the cells during measurement. The surface of the sensor chip is in-plane with the flask surface allowing undisturbed cell growth on the sensor chip. A custom developed rack system allows easy usage of multiple flasks in parallel within an incubator. The presented data demonstrates the application of the SCCF with brain tumor (T98G) and breast cancer (T-47D) cells. Amperometric oxygen sensors were used to monitor cellular respiration with different incubation conditions. Cellular acidification was accessed with potentiometric pH sensors using electrodeposited iridium oxide films. The system itself provides the foundation for electrochemical monitoring systems in 3D cell culture.

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S. Klöppel,, M. Kotschi,, J. Peter,, K. Egger,, L. Hausner,, L. Frölich,, A. Förster,, B.Heimbach,, C. Normann,, W. Vach,, H. Urbach,, Ahmed Abdulkadir
Separating Symptomatic Alzheimers Disease from Depression based on Structural MRI
2018 J Alzheimers Dis, Band: 63, Nummer: 1
G Moras, A Klemenz, T Reichenbach, A Gola, H Uetsuka, M Moseler, L Pastewka
Shear melting of silicon and diamond and the disappearance of the polyamorphic transition under shear
2018 Phys Rev Mater, Band: 2, Seite: 083601
KurzfassungMolecular dynamics simulations of diamond-cubic silicon and carbon under combined shear and compression show the formation of an amorphous solid with liquidlike structure at room temperature. Consistent with the opposite density changes of the two crystals upon melting, the amorphous material is denser than the crystal in silicon and less dense than the crystal in carbon. As a result, its rate of formation is enhanced by pressure in silicon but suppressed in carbon. These results are particularly unexpected for silicon, whose amorphous structure is supposed to be liquidlike only when hydrostatically compressed above the polyamorphic transition pressure (∼14 GPa). Below this pressure, amorphous silicon is expected to have a low-density structure with density close to that of the diamond-cubic crystal. Our simulations show that this polyamorphic transition disappears under shear and high-density, liquidlike amorphous silicon with metallic ductility forms even at low pressure. These results are potentially transferable to other diamond-cubic crystals, like germanium and ice Ih, and provide insights into nonequilibrium materials transformations that govern friction and wear in tribological systems.
Erhardt J, Fuhrer E, Gruschke OG, Leupold J, Wapler MC, Hennig J, Stieglitz T, Korvink JG
Should patients with brain implants undergo MRI?
2018 J Neural Eng
KurzfassungPatients suffering from neuronal degenerative diseases are increasingly being equipped with neural implants to treat symptoms or restore functions and increase their quality of life. Magnetic resonance imaging (MRI) would be the modality of choice for diagnosis and compulsory post-operative monitoring of such patients. However, interactions between the MR environment and implants pose severe health risks to the patient. Nevertheless, neural implant recipients regularly underwent MRI examinations, and adverse events were reported rarely. This should not imply that the procedures are safe. More than 300.000 cochlear implant recipients are excluded from MRI unless the indication outweighs excruciating pain. For 75.000 DBS recipients quite the opposite holds: MRI is considered essential part of the implantation procedure and some medical centres deliberately exceed safety regulations which they referred to as crucially impractical. MRI related permanent neurological dysfunctions in DBS recipients have occurred in the past when manufacturer recommendations were exceeded. Within the last decades extensive effort has been invested to identify, characterise, and quantify the occurring interactions. Today we are far from a satisfying solution to achieve a safe and beneficial MR procedure for all implant recipients. To contribute, we intend to raise awareness of a growing concern and want to summon the community to stop absurdities and instead improve the situation for the increasing number of patients. Therefore, we review implant safety in the MRI literature from an engineering point of view, with a focus on cochlear and DBS implants as success stories in clinical practice. We briefly explain fundamental phenomena which can lead to patient harm, and point out breakthroughs and errors made. We end with conclusions and strategies to avoid future implants from being contraindicated to MR examinations. We believe that implant recipients should enter MRI, but before doing so, we should make sure that the procedure is reasonable.
Glunz Stefan, Feldmann Frank
SiO 2 surface passivation layers – a key technology for silicon solar cells
2018 Solar Energy Materials and Solar Cells, Band: 185, Seite: 260–269
KurzfassungHigh-efficiency silicon solar cells strongly rely on an effective reduction of charge carrier recombination at their surfaces, i.e. surface passivation. Today's industrial silicon solar cells often utilize dielectric surface passivation layers such as SiNx and Al2O3. However, a passivation layer well-known from the microelectronic industry, SiO2, had and has a strong impact on silicon photovoltaics. It allowed to develop the first 20% efficient silicon solar cells in the past and currently experiences a renaissance as the interfacial oxide for silicon-based passivating contacts, thus enabling the next generation of silicon solar cells. This article reviews the properties of SiO2 passivation layers and their strong impact on the historical and current development of silicon solar cells.
L. Becherer, M. Bakheit, S. Frischmann, S. Stinco, N. Borst, R. Zengerle, F. von Stetten
Simplified real-time multiplex detection of loop-mediated isothermal amplification (LAMP) using novel mediator displacement probes with universal reporters
2018 Anal Chem, Band: 90, Seiten: 4741 - 4748
KurzfassungA variety of real-time detection techniques for LAMP based on the change in fluorescence intensity during DNA amplification enable simultaneous detection of multiple targets. However these techniques depend on fluorogenic probes containing target-specific sequences. That complicates the adaption to different targets leading to time-consuming assay optimization. Here, we present the first universal real-time detection technique for multiplex LAMP. The novel approach allows simple assay design and is easy to implement for various targets. The innovation features a mediator displacement probe and a universal reporter. During amplification of target DNA the mediator is displaced from the mediator displacement probe. Then it hybridizes to the reporter generating a fluorescence signal. The novel Mediator Displacement (MD) detection was validated against state-of-the-art molecular beacon (MB) detection by means of a HIV-1 RT-LAMP: MD surpassed MB detection by accelerated probe design (MD: 10 min, MB: 3-4 h), shorter times to positive (MD 4.1±0.1 min shorter than MB, n = 36), improved signal to noise fluorescence ratio (MD: 5.9±0.4, MB: 2.7±0.4; n = 15) and showed equally good or better analytical performance parameters. The usability of one universal mediator-reporter set in different multiplex assays was successfully demonstrated for a biplex RT-LAMP of HIV-1 & HTLV-1 and a biplex LAMP of Haemophilus ducreyi & Treponema pallidum, both showing good correlation between target concentration and time to positive. Due to its simple implementation it is suggested to extend the use of the universal mediator-reporter sets to the detection of various other diagnostic panels.
L. Becherer, N. Borst, R. Zengerle, F. von Stetten
Simultaneous detection of HIV and HTLV by mediator displacement loop-mediated isothermal amplification
2018 6th World Congress on Control and Prevention of HIV/AIDS, STDs & STIs, Zürich/Switzerland, 27. – 28.08.2018
Kurzfassung6th World Congress on Control and Prevention of HIV/AIDS, STDs & STIs, Zürich/Switzerland, 27. – 28.08.2018
J. Madjarov, A. Götze, R. Zengerle, S. Kerzenmacher
Simultaneous use of a crossflow filtration membrane as microbial fuel cell anode – permeate flow leads to 4-fold increased current densities
2018 Bioresource Technol, Band: 257, Seiten: 274 - 280
KurzfassungA new concept for the combination of membrane bioreactors and microbial fuel cells is introduced, that aims at the production of electricity for reducing the overall energy consumption of wastewater treatment. In contrast to previous approaches, the anode is integrated as microfiltration membrane in sidestream crossflow configuration. Using a stainless steel filtration membrane with G. sulfurreducens and an acetatebased synthetic medium, up to 4-fold higher current densities are achieved. In a standard setup without filtration, a membrane of filter grade 1 μm shows current densities of 5.8 A m-2 ± 0.5 A m-2 compared to >11 A m-2 when it is used simultaneously as membrane filter. With smaller pore sizes of filter grade 0.5 μm 4.4 A m-2 ± 0.5 A m-2 in a standard setup and >15 A m-2 in a filtration setup are achieved. The permeate flow was identified as the main parameter leading to increased current densities.
Petrini FM, Valle G, Strauss I, Granata G, Di Iorio R, D'Anna E, Cvancara P, Mueller M, Carpaneto J, Clemente F, Controzzi M, Bisoni L, Carboni C, Barbaro M, Iodice F, Andreu D, Hiairrassary A, Divoux JL, Cipriani C, Guiraud D, Raffo L, Fernandez E, Stieglitz T, Raspopovic S, Rossini PM, Micera S
Six-Month Assessment of a Hand Prosthesis with Intraneural Tactile Feedback.
2018 Ann Neurol
KurzfassungObjective Hand amputation is a highly disabling event, which significantly affects quality of life. An effective hand replacement can be achieved if the user, in addition to motor functions, is provided with the sensations that are naturally perceived while grasping and moving. Intraneural peripheral electrodes have shown promising results toward the restoration of the sense of touch. However, the long‐term usability and clinical relevance of intraneural sensory feedback have not yet been clearly demonstrated. Methods To this aim, we performed a 6‐month clinical study with 3 transradial amputees who received implants of transverse intrafascicular multichannel electrodes (TIMEs) in their median and ulnar nerves. After calibration, electrical stimulation was delivered through the TIMEs connected to artificial sensors in the digits of a prosthesis to generate sensory feedback, which was then used by the subjects while performing different grasping tasks. Results All subjects, notwithstanding their important clinical differences, reported stimulation‐induced sensations from the phantom hand for the whole duration of the trial. They also successfully integrated the sensory feedback into their motor control strategies while performing experimental tests simulating tasks of real life (with and without the support of vision). Finally, they reported a decrement of their phantom limb pain and a general improvement in mood state. Interpretation The promising results achieved with all subjects show the feasibility of the use of intraneural stimulation in clinical settings. Ann Neurol 2018; 1–18
Stieglitz T, Müller M, Boretius T, Micera S, Granata G, Rossini PM, Cvancara P
Stability of miniaturized neural interfaces.
2018 Gordon Research Conference on Neuroelectronic Interfaces, 25.-30.03.2018, Galveston, TX, USA
Seifaei M, De Dorigo D, Fleig D, Kuhl M, Zschieschang U, Klauk H, Manoli Y
Stable, Self-Biased and High-Gain Organic Amplifiers with Reduced Parameter Variation Effect
2018 Proceedings of the IEEE Asian Solid-State Circuits Conference (A-SSCC), Seiten: 119 - 122
F. Balle, T. Beck, D. Eifler, J.H. Fitschen, S. Schuff, G. Steidl
Strain analysis by a total generalized variation regularized optical flow model
2018 Inverse Probl Sci En

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Jünger F, Rohrbach A
Strong cytoskeleton activity on millisecond timescales during particle binding and uptake revealed by ROCS microscopy
2018 Cytoskeleton, Band: 75, Seiten: 410 - 424

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A Gola, L Pastewka
Structure of Interfaces in Cu|Au Nanolaminates
In: NIC Symposium 2018 - Proceedings
2018, Forschungszentrum Jülich, Seiten: 247 - 254, ISBN: 978-3-95806-285-6
KurzfassungWe used molecular dynamics calculations to study the influence of interdiffusion on the bicrystal interface of Cu|Au nanolaminates. Starting from an ideal bicrystal of 50 nm thickness with a {111} semi-coherent interface, we created a diffusive interface region and annealed the system at 1000K. We report the resulting interfacial crystallographic defects as a function of interface width. Our results show an increase of dislocation spacing as the interface becomes more diffuse. The most diffuse interfaces of ~10 nm width studied here form stacking fault tetrahedra.
Widyaya T., Riga E. K., Müller C, Lienkamp K.
Submicrometer-Sized, 3D Surface-Attached Polymer Networks by Microcontact Printing: Using UV-Cross-Linking Efficiency To Tune Structure Height
2018 Macromolecules, Band: 51, Seiten: 1409 - 1417
Boehler C, Schopf A, LealOrdonez J, Asplund M
Super-Capacitive Conducting Polymer Electrodes Can Control Cell Migration Via DC Stimulation.
2018 ”, 40th International Conference of the IEEE Engineering in Medicine and Biology Society, 17.-21.07.2018, Oahu, Hawaii, USA
Ruh D, Mutschler J, Michelbach M, Rohrbach A
Superior contrast and resolution by image formation in rotating coherent scattering (ROCS) microscopy
2018 Optica, Band: 5, Nummer: 11, Seiten: 1371 - 1381

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Bockhorst T, Pieper F, Engler G, Stieglitz T, Galindo-Leon E, Engel AK
Synchrony surfacing: Epicortical recording of correlated action potentials.
2018 Eur J Neurosci, Band: 48, Nummer: 12, Seiten: 3583 - 3596
KurzfassungSynchronous spiking of multiple neurons is a key phenomenon in normal brain function and pathologies. Recently, approaches to record spikes from the intact cortical surface using small high-density arrays of microelectrodes have been reported. It remained unaddressed how epicortical spiking relates to intracortical unit activity. We introduced a mesoscale approach using an array of 64 electrodes with intermediate diameter (250 μm) and combined large-coverage epicortical recordings in ferrets with intracortical recordings via laminar probes. Empirical data and modelling strongly suggest that our epicortical electrodes selectively captured synchronized spiking of neurons in the cortex beneath. As a result, responses to sensory stimulation were more robust and less noisy compared to intracortical activity, and receptive field properties were well preserved in epicortical recordings. This should promote insights into assembly-coding beyond the informative value of subdural EEG or single-unit spiking, and be advantageous to real-time applications in brain-machine interfacing.
Bosh N, Deggelmann L, Blattert C, Mozaffari Jovein H, Müller C
Synthesis and characterization of Halar® polymer coating deposited on titanium substrate by electrophoretic deposition process Corresponding
2018 Surf Coat Tech, Band: 347, Seiten: 369 - 378
E. Kipf, J. Erben, R. Zengerle, J. Gescher, S. Kerzenmacher
Systematic investigation of anode materials for microbial fuel cells with the model organism G. sulfurreducens
2018 Bioresource Technology Reports, Band: 2, Seiten: 29 - 37
KurzfassungDifferent carbon and metal-based anode materials for microbial fuel cells were systematically investigated with a pure culture of the model organism G. sulfurreducens. The highest limiting current density of 756 ± 15 μA cm-2 at -0.253 ± 0.037 V vs. SCE was achieved with graphite foil using a step-wise galvanostatic technique. But also the application of completely different anode materials such as activated carbon cloth, stainless steel and graphite felt led to similar high limiting current densities, suggesting that G. sulfurreducens is able to use a large range of substantially different anode materials as external electron acceptor. Additionally, we could show that a step-wise galvanostatic technique to record polarization curves yields similar current densities as potentiostatic control at -0.400 V vs. SCE with the investigated carbon-based materials. In case of stainless steel these techniques yield slightly different results, presumably due to an effect related to the material’s surface properties.
T. A. Kohl, M. Beutler, M. Merker, T. Paprotka, K. Rönsch, M. Schmitt, W. Grasse, C. Metzger-Boddien, K. Dormanns, J. Lüddecke, N. Paust, J. Schlanderer, L. Delamotte, J. Schickedanz, M. Steinwand, S. Niemann, H. Hoffmann
TB-SeqDisK: A microfluidics platform in combination with next generation sequencing for ultra-fast notification of Mycobacterium tuberculosis and its resistance pattern
2018 39th Annual Congress of European Society of Mycobacteriology, Dresden, 01. – 04.07.2018
, Artemij Amiranashvili,, A. Dosovitskiy,, V. Koltun,, Thomas Brox
TD or not TD: Analyzing the Role of Temporal Differencing in Deep Reinforcement Learning
2018
Castellini C, Kõiva R, Pasluosta C, Viegas C, Eskofier BM
Tactile Myography: An Off-Line Assessment of Able-Bodied Subjects and One Upper-Limb Amputee
2018 Technologies, Band: 66, Nummer: 2
KurzfassungHuman-machine interfaces to control prosthetic devices still suffer from scarce dexterity and low reliability; for this reason, the community of assistive robotics is exploring novel solutions to the problem of myocontrol. In this work, we present experimental results pointing in the direction that one such method, namely Tactile Myography (TMG), can improve the situation. In particular, we use a shape-conformable high-resolution tactile bracelet wrapped around the forearm/residual limb to discriminate several wrist and finger activations performed by able-bodied subjects and a trans-radial amputee. Several combinations of features/classifiers were tested to discriminate among the activations. The balanced accuracy obtained by the best classifier/feature combination was on average 89.15% (able-bodied subjects) and 88.72% (amputated subject); when considering wrist activations only, the results were on average 98.44% for the able-bodied subjects and 98.72% for the amputee. The results obtained from the amputee were comparable to those obtained by the able-bodied subjects. This suggests that TMG is a viable technique for myoprosthetic control, either as a replacement of or as a companion to traditional surface electromyography.
S. Vierrath, M. Klingele, S. Thiele, R. Zengerle, M. Breitwieser
Tailoring the membrane│electrode interface: a review and perspective of novel engineering approaches
2018 69th Annual Meeting of the International Society of Electrochemistry (ISE), Bologna/Italy, 02. – 07.09.2018
Kurzfassung69th Annual Meeting of the International Society of Electrochemistry (ISE), Bologna/Italy, 02. – 07.09.2018
Maxim Tatarchenko, J. Park, V., Koltun, Q. Zhou
Tangent Convolutions for Dense Prediction in 3D
2018 IEEE
Sileo L, Bitzenhofer S H, Spagnolo B, Pöpplau J A, Holzhammer T, Pisanello M, Pisano F, Bellistri E, Maglie E, De Vittorio M, Ruther P, Hanganu-Opatz I L, Pisanello F
Tapered fibers combined with a multi-electrode array for optogenetics in mouse medial prefrontal cortex
2018 Front Neurosci-switz, Band: 12, Ergänzungsband: e771
J. Riba, S. Zimmermann, P. Koltay
Technologies for Automated Single Cell Isolation
In: Handbook of Single Cell Technologies
2018, Springer Nature, T. S. Santra, F.-G. Tseng, T. S. Santra, F.-G. Tseng, ISBN: 978-981-10-4857-9
KurzfassungThe isolation of individual cells has gained tremendous importance with the advent of new methods for highly parallel single-cell analysis. A prerequisite for effective clonal cultivation or single-cell analysis is the efficient isolation of individual cells from liquid cell suspensions. This review provides an overview of technologies that are used to automate the isolation of single cells for subsequent cultivation or analysis. First, currently available technologies are classified based on their major technical characteristics. Then, the most prominent technologies such as limiting dilution, FACS, single-cell printing, hydrodynamic trapping, droplet microfluidics, and cell manipulation by external forces are described in detail. Furthermore, the individual features of each technology with focus on throughput, isolation efficiency, level of automation, flexibility in terms of cell types, and their suitability for specific downstream processing and analysis methods are discussed. In contrast to previous works, this review provides a classification approach for single-cell isolation technologies according to performance requirements, makes specific reference to methods for the isolation of microbial cells, and discusses sample input requirements, which is an important aspect in particular for diagnostic purposes.
S. Hin, N. Paust, M. Keller, M. Rombach, O. Strohmeier, R. Zengerle, K. Mitsakakis
Temperature change rate actuated bubble mixing for homogeneous rehydration of dry pre-stored reagents in centrifugal microfluidics
2018 Lab Chip, Band: 18, Seiten: 362 - 370
KurzfassungIn centrifugal microfluidics, dead volumes in valves downstream of mixing chambers can hardly be avoided. These dead volumes are excluded from mixing processes and hence cause a concentration gradient. Here we present a new bubble mixing concept which avoids such dead volumes. The mixing concept employs heating to create a temperature change rate (TCR) induced overpressure in the air volume downstream of mixing chambers. The main feature is an air vent with a high fluidic resistance, representing a low pass filter with respect to pressure changes. Fast temperature increase causes rapid pressure increase in downstream structures pushing the liquid from downstream channels into the mixing chamber. As air further penetrates into the mixing chamber, bubbles form, ascend due to buoyancy and mix the liquid. Slow temperature/ pressure changes equilibrate through the high fluidic resistance air vent enabling sequential heating/cooling cycles to repeat the mixing process. After mixing, a complete transfer of the reaction volume into the downstream fluidic structure is possible by a rapid cooling step triggering TCR actuated valving. The new mixing concept is applied to rehydrate reagents for loop-mediated isothermal amplification (LAMP). After mixing, the reaction mix is aliquoted into several reaction chambers for geometric multiplexing. As a measure for mixing efficiency, the mean coefficient of variation (C —— V, n = 4 LabDisks) of the time to positivity (tp) of the LAMP reactions (n = 11 replicates per LabDisk) is taken. The C —— V of the tp is reduced from 18.5% (when using standard shake mode mixing) to 3.3% (when applying TCR actuated bubble mixing). The bubble mixer has been implemented in a monolithic fashion without the need for any additional actuation besides rotation and temperature control, which are needed anyhow for the assay workflow.
Li P, Sherman S, Rezem M, Honnef K, Zappe H
Temperature-dependence of polymer grating couplers for single mode waveguides
2018 Proceedings of SPIE, Band: 10535, Seite: 105351R
Feißt M, Möller E, Wilde J
Testchips für die Stressmessung beim Power-Cycling
2018 DVS Berichte, Elektronische Baugruppen und Leiterplatten EBL 2018, Band: 340, Seiten: 113 - 117
Lindauer M, Rijn J, Kotthoff L
The Algorithm Selection Competition Series 2015-17
2018 arXiv, Band: 1805.01214
C Greiner, Z Liu, R Schneider, L Pastewka, P Gumbsch
The origin of surface microstructure evolution in sliding friction
2018 Scripta Mater, Band: 153, Seiten: 63 - 67
KurzfassungA typical tribologically induced microstructure displays a discontinuity parallel to the surface separating the near-surface layer from the bulk. Despite its ubiquitous observation, the origin of this layer underneath the surface remains elusive. Here, we show that already after the first loading pass a localized dislocation structure is found at a depth of 100–150 nm. This structure is linked to the inhomogeneous stress field under the moving indenter, where dislocations are trapped when the stress drops below the material's yield stress. Control of the initial tribological loading could therefore be exploited to design surfaces and materials with superior tribological properties.
L. Becherer
Therapiebegleitende HIV- und HTLV-Diagnostik am Point-of-Care
2018 microTEC Südwest Clusterkonferenz 2018, 16. – 17.04.2018, Freiburg
Kilias A, Haussler U, Heining K, Froriep UP, Haas CA, Egert U
Theta frequency decreases throughout the hippocampal formation in a focal epilepsy model.
2018 Hippocampus, Band: 28, Nummer: 6, Seiten: 375 - 391
D. Kainz, S. Früh, T. Hutzenlaub, R. Zengerle, N. Paust
Total flow control for lateral flow tests with centrifugal microfluidics
2018 MicroTAS 2018, 11. -15. November 2018, Kaohsiung / Taiwan
N. P. Kocatürk-Schumacher, J. Madjarov, P. Viwatthanasittiphong, S. Kerzenmacher
Toward an Energy Efficient Wastewater Treatment: Combining a Microbial Fuel Cell/Electrolysis Cell Anode With an Anaerobic Membrane Bioreactor
2018 Frontiers in Energy Research, Band: 6, Seite: 95
KurzfassungRecently, it has been shown that combining a bioelectrochemical system (BES) with an anaerobic membrane bioreactor (AnMBR) to produce electricity can reduce the overall energy consumption of wastewater treatment. In this study, we tested the recently proposed concept that integrates a microbial anode into an AnMBR, under application relevant conditions, for the treatment of synthetic brewery wastewater. We developed two system configurations: a filtering anode with stainless steel filter plate; and a hybrid anode, in which a polymeric membrane is combined with stainless steel mesh. As fouling is problematic in AnMBRs, we investigated the effect of two fouling mitigation methods, namely electrochemical cleaning and application of a turbulence promotor, on the permeate fluxes and current densities.We also investigated the effect of cathode (counter electrode) position on the permeate fluxes and current densities in filtering and hybrid anode. Our results revealed that permeate fluxes were influenced by the membrane pore size; and dropped below 5 L m−2 hr−1 on day 3 with filter grade 0.5μm; whereas similar values of permeate flux were observed after 5 days of operation with the membrane with filter grade 0.1μm. COD removal across the membrane reached up to 644mg L−1 indicating improvement in energy efficiency and effluent quality of the AnMBR. The location of cathode did not influence permeate fluxes and current densities, but permeate pH was largely affected. Electrochemical cleaning improved permeate fluxes more than 2-fold (18.9 L m−2 hr−1 after 7 days of operation) compared to the operation of the 0.1μm membrane without a cleaning procedure. Application of a turbulence promotor increased permeate fluxes and current densities in filtering anode. The hybrid anode resulted in similar current densities, but higher permeate fluxes as compared to the filtering anode, which dropped below 20 L m−2 hr−1 only after 8 days of operation. The Kocatürk-Schumacher et al. Microbial Anode Combined With AnMBR hybrid anode configuration is an attractive option that combines high permeate fluxes on conventional non-conductive filters with current generation on an inexpensive conductive material. In summary, our results demonstrate that combining BES with AnMBR is a promising approach toward an energy efficient wastewater treatment.
P. Juelg, M. Specht, E. Kipf, M. Lehnert, C. Eckert, N. Paust, F. von Stetten, R. Zengerle, T. Hutzenlaub
Towards Standardization of Molecular Diagnostic Workflows: Centrifugal Microfluidic Automation of qPCR for Cancer Monitoring
2018 6th International Molecular Diagnostics Europe, Lissabon / Portugal, 22. - 24. 05.2018
P. Koltay
Towards a generic 3D-Bioprinting Platform
2018 International Conference on Biofabrication, Würzburg, 28. – 31.10.2018
Kurzfassung; “”, (2018), International Conference on Biofabrication, Würzburg, 28. – 31.10.2018
T Graunke, K Schmitt, S Busch, S Raible, J Wöllenstein
Towards an Empirical Model for the Prediction of the Selectivity of Polymer Membranes
2018 Eurosensors 2018, Graz, Austria , Band: 2, Nummer: 13, Seite: 979
KurzfassungPolymer membranes are often used in combination with gas sensors for selectivity enhancement, especially with metal-oxide sensors (MOX). We report on the development of an empirical model to predict the gas separation properties of polymer membranes. This model is based on the two parameters sorption and diffusion, represented by the polar fraction of the free surface energy (SFE), and the water absorption combined with the molecule diameter based on Lennard-Jones. We measured the surface tension for a number of common fluoropolymers and used the results to determine their SFE using the graphical method developed by van Oss—Chaudhury—Good, compared them with literature data and further optimized the model. With the optimized model, combined with the information on functional groups in the polymers, we are able to predict the selectivity of polymer membranes.
M. Mu’min Solihul, T. Böhm, S. Thiele, M. Breitwieser
Towards more hydrophilic proton exchange membranes: adjusting the wetting properties by electrospinning PVDF-HFP/PVP blends
2018 ELEN Electrospinning for Energy, Montpellier / Fracne, 13. - 15.06.2018
Florian Schindler, Andreas Fell, Ralph Müller, Jan Benick, Armin Richter, Frank Feldmann, Patricia Krenckel, Stephan Riepe, Martin C Schubert, Stefan W Glunz
Towards the efficiency limits of multicrystalline silicon solar cells
2018 Sol Energ Mat Sol C, Band: 185, Seiten: 198 - 204
KurzfassungIn this contribution, we present our recent results for high efficiency multicrystalline silicon solar cells. Based on n-type high-performance multicrystalline silicon substrates in combination with the TOPCon solar cell concept featuring a full area passivating back contact and a boron-diffused emitter as well as a plasma-etched black-silicon texture at the front side, a certified conversion efficiency of 22.3% has been achieved, which is currently the world record efficiency for multicrystalline silicon solar cells. A detailed loss analysis of the record solar cell batch discloses the nature of the remaining loss mechanisms, revealing the route for further improvements. We observe an efficiency gap between the multicrystalline and the FZ reference solar cells of ~1%abs. Compared to the FZ reference cells, the mc-Si cells also feature a significantly larger scattering in Voc and Jsc as well as a fill factor loss of ~1.5%abs. We show that the scattering in Jsc correlates with the area fraction of recombination-active structural crystal defects and the scattering in Voc additionally with lateral emitter-induced inhomogeneities. The fill factor loss is attributed to the general presence of strongly recombination-active grain boundaries. A detailed loss analysis of the record mc-Si solar cell shows that the major electrical losses are due to recombination at grain boundaries (0.7%abs) and recombination in the emitter (0.6%abs). By reducing these electrical loss channels, e.g. by an improved crystallization process together with a hydrogenation of the bulk and application of an adapted emitter, we expect to reach efficiencies for mc-Si solar cells in the range of 23%.
Feißt M, Yu J, Wilde J
Transient Liquid Phase Bonding Using AgSn-Alloys for Stress Reduced Sensor Mounting
2018 IEEE 68th Electronic Components & Technology Conference (ECTC), San Diego, Ca, Seiten: 293 - 300
Ledernez L, Bruch R, Altenburger M, Bergmann M, Urban G
Transient Spark for Bacterial Cleaning of Dental Microcavities
2018 Plasma Medicine
KurzfassungIn this work, we present a method that can be used for the disinfection of microcavities such as tooth root canals. The device is aimed to be introduced inside the root canal. The parameters are chosen so that it produces ROS to inactivate bacteria and develops little to no temperature increase within the root canal. Its effect on bacteria is demonstrated using E. coli spread on Agar in a Petri dish.
Wang Z, Folwill Y, Cu Nguyen P, Zappe H
Tunable bandpass filter for mid-infrared wavelengths using liquid crystal elastomer actuators
2018 Proceedings of SPIE, Band: 10545, Seite: 105450D
F. Lionetto, C. Mele, P. Leo, S. D'Ostuni, F. Balle, A. Maffezzoli
Ultrasonic spot welding of carbon fiber reinforced epoxy composites to aluminum: mechanical and electrochemical characterization
2018 Compos Part B-eng, Band: 144, Seiten: 134 - 142
Williams M, Jervell A, Hiller D, Zacharias M
Using HCl to Control Silver Dissolution in Metal‐Assisted Chemical Etching of Silicon
2018 Phys Status Solidi A, Band: 215, Nummer: 13, Seite: 1800135
Haering, Ivo, Ramin, Malte vo, Stottmeister, Alexander, Schaefer, Johannes, Vogelbacher, Georg, Brombacher, Bernd, Pfeiffer, Mercy, Restayn, Elena-Maria, Ross, Katharina, Schneider, Johannes, Hiermaier, Stefan
Validated 3D spatial stepwise quantitative hazard, risk and resilience analysis and management of explosive events in urban areas
2018 European Journal of security research, Band: Online First, Seiten: 1 - 37
KurzfassungUrban physical security and resilience with respect to accidental and intentional explosive events are an increasing issue regarding civil safety and security of modern societies and their citizens. Examples include industrial on-site explosions, gas explosions or terrorist attacks. In particular, multiple, simultaneous and maliciously time-coordinated events are an increasing event type such as complex attack events consisting of targeted combinations of improvised explosive devices. The paper presents a comprehensive, tailorable and stepwise process. This includes methodologies for scenario, hazard, damage, exposure, event frequency, risk and resilience analysis that have been developed, refined and praxis-tested over decades. The focus is on a summarizing description of the modern best practice approach, the validation efforts undertaken for each step as well as two detailed case studies for exemplary presentation and overall validation. In a comprehensive table, the present approach is compared with other state-of-the-art approaches. The paper shows a refined process how to systematically improve resilience when using the tool, in particular through barriers at explosive sites and at exposed sites of various geometries. Furthermore, along the presentation a set of quality requirements regarding explosive event risk and resilience analyses are provided as collected over the years from the in-field, user group and engineering science perspective as well as a broad outlook on extension options for the future.
C. Siber, F. Stumpf, J. Schöndube, S. Zimmermann, P. Koltay, L. Lautscham
Velocity field analysis of acoustophoretic focusing in a single-cell printing system
2018 Acoustofluidics, Lille/France, 29. – 31.08.2018
F. Balle, D. Backe
Very High Cycle Fatigue of Carbon Fiber Reinforced Polyphenylene Sulfide at Ultrasonic Frequencies
In: Fatigue of Materials at Very High Numbers of Loading Cycles
2018, Springer Spektrum, H.-J. Christ, Seiten: 441 - 461, H.-J. Christ,
Nikolaus Mayer,, Eddy Ilg,, Philipp Fischer,, C. Hazirbas,, D. Cremers,, Alexey, Dosovitskiy,, Thomas Brox
What Makes Good Synthetic Training Data for Learning Disparity and Optical Flow Estimation?
2018 Int J Comput Vision
Breunig I, Hanka K, Jia Y, Zawilski K.T., Schunemann P.G., Buse K.
Whispering gallery optical parametric oscillators for the mid-infrared spectral range
2018 Nonlinear Frequency Generation and Conversion: Materials and Devices XVII, San Francisco, CA, United States Proceedings of SPIE, Band: 10516, Seite: 105160E
KurzfassungThe tunability of cw optical parametric oscillators can be extended in the mid-infrared spectral range by using whispering gallery resonators (WGRs) made of non-oxide crystals. We demonstrate the fabrication of WGRs from silver gallium selenide, cadmium silicon phosphide and orientation-patterned gallium phosphide with quality factors above 106 . The resonators made of the first two provide optical parametric oscillation in the mid-infrared pumped by a compact laser diode at 1.57 μm wavelength. The wavelength tunability of the device based on silver gallium selenide provides a tuning range beyond 8 μm wavelength. These achievements are considered as the first steps of cw optical parametric oscillators into this important spectral region.
Dimitriadis G, Neto J P, Aarts A, Alexandru A, Ballini M, Battaglia F, Calcaterra L, David F, Fiath R, Frazao J, Geerts J, Gentet L J, Van Helleputte N, Holzhammer T, van Hoof C, Horvath D, Lopes G, Maris E, Marques-Smith A, Marton G, Meszena D, Mitra S, Musa S, Neves H, Nogueira J, Orban G A, Pothof F, Putzeys J, Raducanu B, Ruther P, Schroeder T, Singer W, Tiesinga P, Ulbert I, Wang S, Welkenhuysen M, Kampff A R
Why not record from every channel with a CMOS scanning probe?
2018 bioRxiv
M. Buehler, F. Hegge, P. Holzapfel, S. Thiele
Why porous transport electrodes (PTEs) instead of catalyst-coated-membranes (CCMs)?
2018 69th Annual Meeting of the International Society of Electrochemistry (ISE), Bologna/Italy, 02. – 07.09. 2018
Kurzfassung69th Annual Meeting of the International Society of Electrochemistry (ISE), Bologna/Italy, 02. – 07.09. 2018
Kaiser A.
Wie sich Geschlechtlichkeit in den Neurowissenschaften manifestiert und wie Geschlecht in das Gehirn kommt. Kritische Überlegungen.
2018 In M. Koreuber, & B. Assmann (Eds.), Das Geschlecht in der Biologie. Aufforderung zu einem Perspektivwechsel. (Series Schriften zur interdisziplinären Frauen- und Geschlechterforschung), Band: 12, Seiten: 133 - 150
Böhm T, Joseph K, Kirsch M, Moroni R, Hilger A, Manke I, Johnston M, Asplund M, Vomero M, Hofmann UG, Stieglitz T, Haas CA, Thiele S
X-ray tomographic 3D reconstruction of the brain-probe-interface in rat cortex.
2018 Gordon Research Conference on Neuroelectronic Interfaces, 25.-30.03.2018, Galveston, TX, USA
Tanvir N, Yurchenko O, Laubender E, Pohlec R, Sicard O v, Urban G
Zinc peroxide combustion promoter in preparation of CuO layers for conductometric CO₂ sensing
2018 Sensor Actuat B-chem, Band: 257, Seiten: 1027 - 1034
KurzfassungThe detection of CO₂ has applications for both industrial and domestic use due to its high exposure effects on the human health. Conductivity sensors on the other hand, present a cost-effective approach that can be successfully utilized for the detection of CO₂. However, the integration of metal oxide based nanoparticles layers for conducometric sensing is complicated and requires improvement in the layer quality to achieve effective and stable gas sensing properties. Addressing this challenge, we present in this work, p-type semiconducting CuO nanoparticles as a CO₂ gas sensitive material and introduce a combination of organic binder and peroxide such as ZnO₂ for improved gas sensitive layer quality. The addition of ZnO₂ to CuO nanoparticles enables the layers annealing at 300 °C which makes the preparation method compatible to silicon based gas sensing devices. For the characterization of layers, X-ray diffraction, scanning electron microscopy, thermogravimetric analysis and Fourier transform infrared measurements are employed. The CO₂ gas sensing measurements show a reversible change in resistance suggesting hybrid nanoparticles layers as an efficient gas sensitive material. The measurements performed at different humidity levels for CuO-ZnO₂ (10:1) layer indicate different sensing mechanism for dry conditions in comparison to the measurements performed under humid atmosphere. The Lewis acid-base reaction between oxide oxygen and CO₂ has been proposed as sensing mechanism for the measurements in dry air, whereas the formation of surface barriers between nano-grains due to the reaction with CO₂ has been suggested for the CO₂ response under humid conditions.

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