Aktuelle Publikationen der Technischen Fakultät

Jahre: 2018

2018

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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 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
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
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
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 Kochte, Ahmed Atteya, Laura Rodriguez Gomez, Hans-Joachim Wunderlich, Bernd Becker, Matthias Sauer
Detecting and Resolving Security Violations in Reconfigurable Scan Networks
2018 IEEE Int'l Online Testing Symp
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.
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
Florian Staab, Frank 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
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.
Florian Staab, Frank 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, Azzar 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), accepted for publication
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)
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
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.
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, Seite: 1
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.
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.
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
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.
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
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 Neurla Probe with 1600 Close-packed Recording Sites and 32 Analog Outpt 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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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
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.
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.
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 accepted for publication and presentation in ANALOG 2018
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, Feißt M, 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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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.
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
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.
N. Bosh, H. Mozaffari-Jovein, C. Müller
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.

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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
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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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.
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
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.
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 accepted for publication and presentation in 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.
Backe S., Balle F., Hannemann B., Schmeer S., Breuer U.P.
Fatigue properties of multifunctional metal‐ and carbon‐fibre‐reinforced polymers and intrinsic capabilitiesfor damage monitoring
2018 Fatigue Fract Eng M
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
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
arXiv preprint, 2018
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, 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
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), accepted for publication
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 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.
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
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].
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, Claas Müller, Holger Reinecke
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.
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.
Savelli G, Colonna J, Faucherand P, Wendler D, Manoli Y, Keller M
Integrated Thermoelectric Sensors for Thermal Monitoring of Integrated Circuits
2018 accepted for publication and presentation in 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
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
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
Koch M D, Rohrbach A
Label-free imaging and bending analysis of microtubules by ROCS microscopy and optical trapping
2018 Biophys J, Band: 114, Nummer: 1, Seiten: 168 - 177

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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.
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.
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.
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.
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.
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
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.
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
Kermani H, Rohrbach A
Orientation-control of two plasmonically-coupled nanoparticles in an optical trap
2018 Acs Photonics, Band: in press
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.
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
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
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.
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
arXiv preprint, 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.
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.
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.
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 accepted for publication and presentation in IEEE Asian Solid-State Circuits Conference 2018 (ASSCC)
Frank Balle, Tilmann Beck, Dietmar Eifler, Jan Henrik Fitschen, Sebastian Schuff, Gabriele 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

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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.
Ruh D, Mutschler J, Michelbach M, Rohrbach A
Superior contrast and resolution by image formation in rotating coherent scattering (ROCS) microscopy
2018 submitted
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.
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
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
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
M.S. Mu’min, 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
Francesca Lionetto, Claudio Mele, Paola Leo, Sonia D'Ostuni, Frank Balle, Alfonso 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
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
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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