Hasani-Sadrabadi M.M.,Georgia Institute of Technology |
Hasani-Sadrabadi M.M.,Institute of Microengineering |
Hasani-Sadrabadi M.M.,Ecole Polytechnique Federale de Lausanne |
Coullerez G.,Ecole Polytechnique Federale de Lausanne |
And 6 more authors.
ACS Applied Materials and Interfaces | Year: 2014
Polyelectrolyte-coated magnetic nanoparticles were prepared by decorating the surface of superparamagnetic iron oxide nanoparticles (SPIONs) with crosslinked chitosan oligopolysaccharide (CS). These positively charged particles (CS-SPIONs) were then added to a negatively charged polymer (Nafion), and cast into membranes under an applied magnetic field. TEM and SAXS measurements confirmed this process created aligned, cylindrical nanodomains in the membranes. This was also indirectly confirmed by proton conductivity values. The strong electrostatic interaction between chitosan and Nafion prevented oxygen permeability and water evaporation at elevated temperatures through the proton conductive channels. The resultant proton exchange membranes showed lower conduction dependency to relative humidity, which is highly desirable for hydrogen fuel cells. The fuel cell performance tests were performed on the designed polyelectrolyte membrane by hydrogen-oxygen single cells at elevated temperature (120 °C) and low relative humidity. © 2014 American Chemical Society.
Mastrangeli M.,Distributed Intelligent Systems |
Mastrangeli M.,Institute of Microengineering |
Schill F.,Distributed Intelligent Systems |
Goldowsky J.,Swiss Center for Electronics and Microtechnology |
And 3 more authors.
Proceedings - IEEE International Conference on Robotics and Automation | Year: 2014
Self-Assembly is a key coordination mechanism for large multi-unit systems and a powerful bottom-up Technology for micro/nanofabrication. Controlled self-Assembly and dynamic reconfiguration of large ensembles of microscopic particles can effectively bridge These domains To build innovative systems. In This perspective, we present SelfSys, a novel platform for The automated control of The fluidic self-Assembly of microparticles. SelfSys centers around a water-filled microfluidic chamber whose agitation modes, induced by a coupled ultrasonic actuator, drive The assembly. Microparticle dynamics is imaged, Tracked and analyzed in real-time by an integrated software framework, which in Turn algorithmically controls The agitation modes of The microchamber. The closed control loop is fully automated and can direct The stochastic assembly of microparticle clusters of preset dimension. Control issues specific To SelfSys implementation are discussed, and its potential applications presented. The SelfSys platform embodies at microscale The automated self-Assembly control paradigm we first demonstrated in an earlier platform. © 2014 IEEE.
Kirschbaum M.,Fraunhofer Institute for Biomedical Engineering |
Guernth-Marschner C.R.,Saarland University |
Cherre S.,Fraunhofer Institute for Biomedical Engineering |
De Pablo Pena A.,Institute of Microengineering |
And 8 more authors.
Lab on a Chip - Miniaturisation for Chemistry and Biology | Year: 2012
The prospect of novel therapeutic approaches has renewed the current interest in the fusion of rare cells, like stem cells or primary immune cells. While conventional techniques are only capable of mass fusion, lab-on-a-chip systems often still lack an acceptable method for making the cells available after processing. Here, we present a microfluidic approach for electrofusion on the single-cell level that offers high control over the cells both before and after fusion. For cell pairing and fusion, we employed dielectrophoresis and AC voltage pulses, respectively. Each cell has been characterized and selected before they were paired, fused and released from the fluidic system for subsequent analysis and cultivation. The successful experimental evaluation of our system was further corroborated by numerical simulations. We obtained fusion efficiencies of more than 30% for individual pairs of mouse myeloma and B cell blasts and showed the proliferating ability of the hybrid cells 3 d after fusion. Since aggregates of more than two cells can be fused, the technique could also be developed further for generating giant cells for low-noise electrophysiology in the context of semi-automated pharmaceutical screening procedures. © 2012 The Royal Society of Chemistry.
Mastrangeli M.,Institute of Microengineering |
Mastrangeli M.,Ecole Polytechnique Federale de Lausanne |
Mastrangeli M.,Roosevelt University |
Martinoli A.,Ecole Polytechnique Federale de Lausanne |
Brugger J.,Institute of Microengineering
Microelectronic Engineering | Year: 2014
Self-assembly (SA) is a bio-inspired key coordination mechanism for swarms of intelligent agents as well as a pervasive bottom-up methodology for the fabrication of heterogeneous micro- and nanosystems. Analytical studies of SA at small scales are therefore highly relevant for many technological applications. In this paper we present an innovative design and fabrication process for three-dimensional polymeric microtiles conceived as passive vehicles to investigate the dynamics of fluidic SA at sub-millimeter scale. The microtiles are fabricated out of the superposition of two structural SU-8 layers featuring chiral copies of the same centro-symmetric pattern. They can coordinate laterally in water independently of their vertical orientation to form close-packed square lattice clusters. The microtiles embed a central marker enabling the real-time optical tracking and automated closed-loop control of their fluidic SA. The fabrication process makes use of a thick sacrificial copper layer and allows the wafer-level batch production of tens of thousands of microtiles, in line with the massively parallel nature of SA. © 2014 Elsevier B.V. All rights reserved.
Paviet-Salomon B.,PV Center |
Tomasi A.,Institute of Microengineering |
Descoeudres A.,PV Center |
Barraud L.,PV Center |
And 4 more authors.
IEEE Journal of Photovoltaics | Year: 2015
We analyze the optical losses that occur in interdigitated back-contacted amorphous/crystalline silicon heterojunction solar cells. We show that in our devices, the main loss mechanisms are similar to those of two-side contacted heterojunction solar cells. These include reflection and escape-light losses, as well as parasitic absorption in the front passivation layers and rear contact stacks. We then provide practical guidelines to mitigate such reflection and parasitic absorption losses at the front side of our solar cells, aiming at increasing the short-circuit current density in actual devices. Applying these rules, we processed a back-contacted silicon heterojunction solar cell featuring a short-circuit current density of 40.9 mA/cm2 and a conversion efficiency of 22.0%. Finally, we show that further progress will require addressing the optical losses occurring at the rear electrodes of the back-contacted devices. © 2011-2012 IEEE.
Ruan J.J.,Institute of Microengineering |
Lockhart R.A.,Institute of Microengineering |
Janphuang P.,Institute of Microengineering |
Quintero A.V.,Institute of Microengineering |
And 2 more authors.
IEEE Transactions on Instrumentation and Measurement | Year: 2013
This paper presents an automated test bench, based on a rigorous measurement procedure, used to fully characterize vibration energy harvesters including determination of the resonance frequency, impedance, optimal load, and output power as a function of both frequency and acceleration. The potential of this method and the performance of the automated test bench allows systematic data acquisition which is essential for a good comparison of all harvesters. A dedicated automation circuit was designed and fabricated. It uses stepper motors to mechanically control trimmers to vary the resistive load and reed relays to switch between the measurement sequences. With this, the setup is able to determine the optimal load of the device-under-test at its resonant frequency for a given acceleration. The test bench was used to fully characterize several types of vibration harvesters fabricated on both silicon and polymeric substrates. A comparison of the characterized devices is discussed using a figure of merit proposed here. A survey and compilation of current practices used to benchmark vibration harvesters is also reported. © 2013 IEEE.
Ayyalasomayajula P.,Institute of Microengineering |
Grassi S.,Institute of Microengineering |
Farine P.-A.,Institute of Microengineering
European Signal Processing Conference | Year: 2011
In this paper we propose a low complexity method for Rotation, Scale and Translation (RST) invariant content-based image retrieval, suitable for a handheld image recognition device. The RST compensation method is based on Fourier-Mellin Transform (FMT) which we implement efficiently using log-polar grid interpolation. This RST compensation method is used in conjunction with an image recognition algorithm-based on Discrete Cosine Transform (DCT) phase matching. A pre-selection algorithm is also added for de-creasing the complexity. This algorithm is based on color proportions within concentric circular zones encompassing the edge pixels. The resulting RST invariant image recognition system was tested on 1500 pictograms and 1000 pictures with different RST conditions, showing an average recognition accuracy of 95.2% for pictograms and 96.9% for pictures. © 2011 EURASIP.
Gijs M.A.M.,Ecole Polytechnique Federale de Lausanne |
Gijs M.A.M.,Institute of Microengineering |
Lacharme F.,Ecole Polytechnique Federale de Lausanne |
Lehmann U.,Ecole Polytechnique Federale de Lausanne
Chemical Reviews | Year: 2010
Advances in the fabrication, manipulation, detection, and application of magnetic particles in microfluidic systems were studied. Nearly all important functions in a bioassay can be realized using magnetic beads, raw sample purification, providing a solid substrate to the sample, mixing, labeling, manipulation, transport, and separation. Magnetic labeling permits one to select or deplete certain cell types from a complex matrix, because of the combination of magnetic labeling with magnetic separation principles. When introducing a raw cell sample on a microfluidic chip or cartridge, it is possible to capture the DNA, purify and process it, and detect a specific DNA sequence on-chip. Microfluidic chips for nucleic acid detection will be playing an important role for point-of-care diagnosis and infield testing. Optimized chemical reaction/washing protocols have been developed for magnetoresistive sensors, where the magnetic particles need to be immobilized specifically over the most sensitive part of the sensor area.