Wide bandgap materials: from quantum to classical
Anna Ermakova, CTR
Due to the high thermal and chemical stability wide bandgap materials such as diamond and silicon carbide attract more and more attention. From one side such materials are interesting for electronics. Since they can find a lot of applications in harsh environment. From another point of view they are good matrixes to „freeze“ single atom system at room temperature, which can be used for quantum computing and not only. I am going to discuss one atom-like point center in diamond – nitrogen-vacancy (NV) defect. It is optically active center with non-zero spin. NV center can be used as an optical marker for biological systems, due to nontoxicity and high biocompatibility of diamond. Also it can be used for magnetic field detection, including high sensitive NMR measurements.
Label-free visualization and quantification of single cell activity using metal-cald waveguide (MCWG) based microscopy
Thomas Söllradl, CTR
Evanescent-field based methods such as surface plasmon resonance (SPR) have been used very effectively for label-free imaging of microscopic biological material in close proximity to a sensing surface. However, the shallow probing depth of SPR (typically less than ~200 nm) can be problematic when imaging relatively thick biological objects such as cells or bacteria. In this paper, we demonstrate how metal-clad waveguides (MCWG) can be used to achieve deeper probing depth compared to SPR while maintaining good imaging spatial resolution. Comparative numerical simulations of imaging spatial resolution versus probing depth are shown for a number of common SPR, long-range SPR, and MCWG configurations, demonstrating that MCWG offer the best compromise between resolution and depth for imaging thick biological objects. We demonstrate the potential of this approach by monitoring intracellular activity following the activation of apoptosis in individual cells exposed to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and by visualizing and quantifying extracellular changes in endothelial cell layer integrity following the activation of the proteinase-activated receptor 1 (PAR1) by thrombin.
Multiphase Chemistry and Open Access at the Interface of Earth and Life Sciences
Ulrich Pöschl, Prof. Dr., Director of Max Planck Institute for Chemistry , Mainz/Germany
Multiphase chemistry deals with chemical reactions, transport processes and transformations between solids, liquids and gases. These processes are important for Earth system science and climate research as well as for life and health sciences. In Earth system science and climate research, the focus of our department is on studying biological and organic aerosols, aerosol-cloud interactions and atmosphere-surface exchange processes. Concerning life and health sciences, we investigate how protein macromolecules are modified by air pollutants and how this affects allergic reactions and diseases. We try to elucidate the course of multiphase processes at the molecular level and its impact at the macroscopic and global scales. With regard to scientific publishing and communication, we promote open access for efficient dissemination and re-use of scientific knowledge, and multi-stage open peer review for efficient quality assurance through transparency and self-regulation. Further information:
Wafer Level Chip Scale Packaging
Ying Ma, CTR
Wafer Level Packaging (WLP) based on redistribution is the key technology which in evolving to System in Package and Heterogeneous Integration by 3D packaging using TSV. Materials and process technologies are key for a reliable WLP. It’s not only the choice for the right polymer or metal but the interfaces could be even more critical like Under Bump Metallurgy (UBM) or the adhesion of polymers. In my presentation, I would like to share my experience in the field of WLP, including UBM process, wafer level bumping and flip chip assembly.
CTR goes Quantum
Thomas Moldaschl, CTR
Over the last years it has become easier and easier to realize full Quantum mechanical systems in the lab, often without the requirement for ultra-cold and ultra-clean environments. Today there are many proposals for practical QM applications, many of which have been implemented so efficiently that they have reached an industrial level.
At the same time we are at a point where several CTR employees have a QM background. To tap this vast potential of possible future research and funding strategies, our colleague, Thomas Moldaschl, has taken it onto himself to investigate QM applications for sensing technologies. He will present his findings and ideas at the next meeting of the CJC to initiate thought and discussion aiming at the realization of a future CTR Quantum sensor.
Aufbau und Verbindungstechnik: Lehrstuhlpräsentation
Prof. Jürgen Wilde, IMTEK, Albert-Ludwigs-Universität Freiburg
Die Aufbau- und Verbindungstechnik (AVT) verbindet die "Siliziumwelt" des Mikrosystems mit der Systemebene. Die AVT als Lehr- und Forschungsgebiet umfasst die Methoden, Verfahren und Technologien zur Herstellung der Hardware auf den Systemebenen oberhalb des eigentlichen Funktionselementes. Sie hat dabei folgende Aufgaben:
- Schutz des Bauelementes vor der Umgebung
- Versorgung mit elektrischer Energie und mit Daten
- Abführung von Verlustwärme
- optische, mechanische oder fluidische Schnittstelle zu externen Systemen
AVT hat insgesamt maßgeblichen Anteil an Kosten und Wertschöpfung elektronischer Systeme, und beeinflusst in hohem Maße Baugröße, Gewicht, elektrisches und thermisches Verhalten sowie die Zuverlässigkeit eines Gesamtsystems. Die Lebensdauer kann durch das Aufbaukonzept, durch optimierte thermische und thermomechanische Auslegung sowie durch eine geeignete Werkstoffauswahl und angepasste Herstellungsprozesse entscheidend verbessert werden.
Die AVT stellt somit in der MST ein sehr breites und vielfältiges Feld dar, mit Aktivitäten in Forschung und Lehre auf den folgenden Teilgebieten:
- Konzepte zur Integration von Mikrosystemen
- Neue Gehäusetechniken und Werkstoffe
- Montage- und Kontaktierungstechniken
- Methoden für Auslegung und Design
- Qualität und Zuverlässigkeit in der AVT
Applications of integrated optics and surface acoustic waves in sensor and actuator technology
Prof. Dr. Maria Kufner, Coburg University for applied sciences
The institute of sensor and actuator technology (ISAT) of Coburg University of Applied Sciences and Arts in Coburg was founded in 2006. Its research and development activities primarily have been focused on surface acoustic waves, meanwhile supplemented with integrated optics and microfluidics. The topics cover a variety of application areas, such touch sensitivity, non-invasive detection of depositions, coatings or biofilms, non-contact detection of material properties, intelligent condition monitoring, data monitoring. The actuator developments comprise haptic feedback, spray generation, coagulation and mixing of fluids, as well as the acceleration of microscopic transport processes via surface acoustic waves, for example in electro-polishing or charging batteries.
Characterization of Photonic MEMS Sensor in the Mid Infra-Red Spectral Region
Kumar Nithin, CTR / Coburg University of applied sciences
In order to develop a fully CMOS compatible CO2 micro gas sensor based on evanescent field absorption in the mid-infrared, it is essential to first characterize separately the various components of the sensor: the optical waveguide structures, the light source and the detector. The experimental results provide a feedback for the design and fabrication steps, and can be used for the design of improved structures. First, the presentation will give a short introduction about the sensing principle and the experimental methods employed for the optical and electrical characterization of the sensor components. Second, the results of the characterization will be presented, with focus on: (1) Optical characterization of losses in slab waveguide structures. (2) Electrical characterization of the on-chip light source and detector. Finally, a first proof-of-principle measurement of CO2 from structures containing both electrical and optical elements will be presented.
Auch Forschungsprojekte kann man planen – am Beispiel Philips Headquarter Programm
Dr. Roland Waldner, PHILIPS Health Tech
Roland Waldner studied plastics engineering and innovation management at the university of Klagenfurt. He is currently the head of “Advanced Development and Patents” at PHILIPS Health Tech working on innovation management, i.e. invention disclosures, patent applications as well as with project funding application.
Plasmonic Nanoantennas in Visible Regime from Concept to Realization
Abasahl Banafsheh, CTR
Plasmonic nanoantennas are a versatile group of plasmonic structures with a peculiarity of being the interplay between the far-field and the near-field. As the properties of the nanoantennas are firmly tangled to their shape and dimensions, they can be engineer in order to achieve desired functionalities. In my presentation, I will give a short introduction to surface plasmon polaritons and plasmonic nanoantennas, then I will represent an equivalent circuit model in order to conceptualize the functionality of these structures. At the end, I will introduce new families of plasmonic antennas such as circularly polarized antennas, multi-layered antennas, gap-loaded antennas and horn antennas in the visible regime.
X-ray diffraction microscopy for nanoscale imaging of biological samples
Dr. Jan Steinbrener, CTR
X-ray Diffraction Microscopy (XDM) has been gaining in popularity for nanoscale imaging of biological and material science samples. Its high penetration depth (compared to electron microscopy) and its good dose efficiency (compared to its lens-based X-ray alternative) make it uniquely suited for imaging whole biological specimens, where radiation damage is a concern. From a recorded diffraction pattern, the complex exit wave of the object can be recovered using an iterative reconstruction algorithm. In addition to structural information, the resulting data contains depth information of the object along the 2D projection and quantitative phase information. The extension to 3D imaging is straightforward and allows for element-specific reconstruction of the complex object function.
With the advent of X-ray lasers with high power pulses in the femtosecond regime, the technique can be extended to even the most radiation sensitive samples (such as micro-crystals), as the diffraction pattern can be recorded before any structural changes due to radiation damage occur (diffract then destroy). Results of the imaging of yeast cells (freeze-dried and frozen-hydrated) as well as structure determination of micro-crystals using a free-electron laser will be presented.
Porousification of Monocrystalline Silicon Carbide: Methods and Benefit for Novel MEMS Designs
Markus Leitgeb, TU Vienna
The preparation of porous silicon carbide (SiC) layers with wet chemical etching methods from single crystalline SiC wafers is presented. In particular, photochemical and photoelectrochemical etching techniques are studied and evaluated for SiC.
Photochemical etching is achieved with the deposition of platinum electrodes on the surface of SiC and the subsequent exposure of the wafer to an etching solution. Both UV irradiation as well as an oxidant are necessary for etching. The resulting porous layers show light interference effects when investigated optically as well as a reorganization of the porous structure when exposed to high temperatures. Therefore, application scenarios of this approach could be in the field of pressure or optical sensors and are discussed.
Photoelectrochemical etching utilizes an external power source to initiate the formation of a porous layer. The homogeneity of the porous layers is increased by combining photoelectrochemical with photochemical etching. A possible application scenario of porous SiC multilayers in optical sensors is presented.
Ultrafast Spectroscopy of Self-Assembled Quantum Dots
Thomas Moldaschl, CTR
The increasing interest in low dimensional semiconductor nanostructures hosting excitonic or spin qubit carriers leads to the investigation of decoherence mechanisms that are a direct or indirect consequence of light-matter and matter-matter interactions in the semiconductor matrix. Mechanisms are portrayed and possible solutions are presented.
Acoustic Losses Visualization in High-Frequency SAW RF-Filters
Claude Humbert, Supméca Paris
In the frame of telecommunication, surface acoustic waves (SAW) are used to transport information in Radio-Frequency filters (microsystems able to filter an antenna signal). As such filters deal with very low energy (less than 1 mW), it is preferable to prevent any energy leakage during the SAW propagation. Dr Pascal Nicolay and Hugo Chambon wish to understand the causes of such losses in order to optimize these filters. That’s why I had to design and set up an optic device (interferometry) able to measure, with high accuracy and resolution, the amplitude of small wavelength SAW. Of course the CTR could also use it in the future for any other application involving a surface vibration amplitude measurement.
ADVANCED FINITE ELEMENT MODELLING OF A MEMS TRANSDUCER
Antoine Caillard, Ecole Nationale Supérieure d´Ingénieurs du Mans (ENSIM)
Nowadays, a lot of consumer products include microelectromechanical systems (MEMS) in order to answer the constant need to reduce the size of products. For example, cellphones include many MEMS like microphones, accelerometers or gyroscopes. The market is principally focused on pressure sensors and microphones and so, the challenge is to improve the quality while reducing the size of these sensors. When it comes to microphones, the classical way to deal with acoustics, based on the wave propagation equation, is no more accurate because the thermal and viscous effects that appear on the boundaries are not taken into account. This presentation will demonstrate why it is primordial to use the Navier-Stokes equations to accurately describe the phenomena that are appearing when the thermoviscous boundary layers size is of the same magnitude order than the characteristic lengths of such sensors (millimeters). A simple analytical solution will be confronted to the simulation results obtained with COMSOL, with and without taking into account these diffusive effects and, finally, the study of a MEMS microphone will be presented.
Design of a Microfluidic Device for a Smart Enzymatic Biosensor
Margret Leibinger, IMTEK, Universität Freiburg
The broad field of personalized medicine has been becoming more and more important in recent years, but as it is still in its infancy many challenges are to be mastered. One goal of personalized medicine is to determine the exact amount needed of a drug, which varies amongst individuals because metabolism of drugs happens at a different pace in each individual due to different amounts of enzymes present in our liver. For this application a microfluidic measurement chamber was developed that enables a continuous fluid flow as well as the integration of electrodes for electrochemical detection of the concentration of a substrate in a sample fluid. The design of the biosensor was evolved allowing a maximum amount of the sample fluid to get in direct contact with the enzymes immobilized on the working electrode while also respecting the constraints of additive manufacturing techniques at the same time. The electrodes are inkjet-printed using silver ink for the reference electrode whereas graphene ink is used for the working- and counter electrodes. The fluid flow through the measurement chamber was simulated and characterization of the electrodes is being done.
FEM Simulation of MEMS Packages
Alexander Stadler, FH Vorarlberg
One of the most important components in smartphones is the microphone. The microphones are optimized for room temperature. If the temperatures change, the quality of the sound will decrease. The main target of this work is finding a design for the compensation structure, which is able to compensate the thermal effects and, to know about the stresses in the structure. To understand the sound quality it is necessary to develop a small tool to calculate the compliance.
3D Magnetic Steering Wheel Angle and Suspension Travel Detection - A novel application of 3D magnetic sensing techniques to increase vehicle safety decreasing sensor overhead
Bruno Spricigo, Federal university of Santa Catarina
Electronics and control are continuously growing subjects in the automotive industry. The development of new technologies to reduce consumption, increase comfort and handling are the number one priority of many manufactures. Various systems that make nowadays vehicles more secure like TCS (Traction Control System) and ESP (Electronic Stability Program) rely on sensing several variables like individual wheel speed and suspension displacement to compare it to an analytical model and decide if action is needed or not. The main target of this work is to propose a smart use of a new 3D magnetic sensor to improve the quality and precision of the suspension displacement measurement and, because of the greater capabilities of the sensor, detect the steering wheel angle at the same time. The mechanical and magnetic implementations are discussed in detail.
Energy Harvesting: Experimental Determination of the Efficiency of different Energy Sources
Bettina Findenig, Fachhochschule-Kärnten, Villach (Systems Engineering)
Wireless sensor nodes are usually powered by batteries or accumulators, which have a limited operation time and need to be recharged. Energy harvesting therefore offers the possibility to supply a system with freely available energy for making it autark. This work presents current approaches of using energy extracted from the environment to power microelectronic devices. In the first part the main focus is, to determine the amount of energy produced by different energy harvesters using measurements. As a second step, the operation of a micro energy harvesting system is explained and has been tested with a laboratory demonstrator. This demonstrator has been redesigned for an internal demo system of a micro energy harvesting system which shall visualize the effectiveness of the harvesters.
Simulation of IDT-based acoustic devices
Hugo Chambon, Université technologique de Compiègne, CTR
IDT-based acoustic devices use electro mechanic coupling in piezoelectric media to excite propagating waves. Due to the sensitivity of media's wave velocity to temperature, stress and mass loading, these acoustic devices are used as sensors. Such acoustic devices enable passive and wireless detection making them especially good candidates for sensing application in harsh environment. However, the design of acoustic wave sensors is highly iterative because of the large number of parameters to be optimized in addition to the complex electro mechanic interactions.
To shorten development time, several numerical and analytical methods have been developed. The model we present here is based on Finite Element analysis. Because of the high aspect ratio of the geometry, a complete FE simulation of the device would be very time consuming, therefore using the periodicity of the structure, the model is simplified (reduced) to a single pair of fingers. This model enables to compute the harmonic admittance and extract parameters that are used afterward to simulate actual devices.
Capacitive Sensors: From the Principle and Front End Design to Analog and Digital Signal Processing
Prof. Hubert Zangl, Institut für Intelligente Systemtechnologien, Alpen-Adria Universität, Klagenfurt
More than 100 years after the first use of capacitive sensing principles, capacitive sensors are found in billions of products for various applications. As the actual sensor elements are just (more or less) conductive areas, they are of unparalleled simplicity and they can be realized by a variety of manufacturing technologies and materials. While used to cover rather large spatial areas e.g. in touch screens in mobile phones or as replacement of mechanical switches in cars and home appliances, the principle is also used in miniaturized microelectromechanical devices, e.g. in pressure, force and acceleration sensors or for the detection of chemical substances or biological cells.
As capacitive sensor exhibit sensitivities towards many physical parameters they find wide applicability. However, the sensitivity towards many parameters also implies that cross-sensitivities to may be a major concern. Thus, in order to design robust and accurate sensors, the entire chain starting from the electrode topology over the analog measurement circuitry up to the signal processing algorithms used to determine the parameter of interest from the measured capacitances has to be considered. Consequently, the present talk will provide an overview of this entire chain and specifically address reconstruction algorithms (including Electrical Capacitance Tomography) as well as the design strategies for electrode topologies.
Electron microscopy at USTEM, TU Wien
Prof. Johannes Bernardi, USTEM, TU Wien
Biography: Prof. Bernardi studied at the technical university of Vienna. He soon became interested in analytical electron microscopy and during the following years be became engaged in the preparation and microstructure and properties of magnetic materials in the workgroup of Prof. Fidler. During the diploma study about "TEM investigations of Sm-Co 2:17 magnets" he gained experience in that field by industrial training at Treibacher Chemischen Werken and at Magnetfabrik Thyssen in Dortmund.
He was employed as research assistent at the Institute of Applied and Technical Physics, for the BRITE/EURAM project "Analysis of Coercivity and the Microstructure of High-Tech Hard Magnetic Materials" during PhD. Besides microstructural investigations, another main task was the installation of a powder metallurgical lab at the institute. The thesis entitled "Microstructure and Coercivity of Rare Earth - Iron Permanent Magnet Materials" was finished 1993.
After that he moved for two years to USA as an Erwin Schrödinger research fellow. He worked at the Department of Materials Science and Engineering, University of California, Berkeley, and the National Center for Electron Microscopy(NCEM), Lawrence Berkeley with Prof. Gareth Thomas, a pioneer in the field of transmission electron microscopy. During that research visit he investigated single-domain nanophases for GMR applications by high resolution TEM.
Returning to Europe he was employed as a guest scientist at the Institut für Festkörper- und Werkstofforschung in Dresden working on structural investigations of permanent magnet materials until he came back to Vienna University of Technologys in 1996 engaged in the BRITE/EURAM III Projektes "EMERGE".
1998 he became employed as a reasearch assistent in the electron microscopy group at the Institute of Angewandte und Technische Physik, Vienna University of Technology. He was strongly involved in the preparation for the foundation of the service centre USTEM, which was established in 2000 under the guidance of Prof. Schattschneider. 2001 he was assigned to USTEM as a university assistent.
2006 he became head of USTEM.
Reactive Nanocomposites for Bonding Applications
Mathias Kremer, PhD Student, CTR und Karlsruhe Institute of Technology (KIT), Institute of Microstructure Technology (IMT)
Highly reactive integrated material systems have recently gained attention, as they promise a feasible tool for heterogeneous integration of micro electromechanical systems (MEMS). As integrated energy sources they can be used to join heterogeneous materials without applying too much thermal stress to the whole device. Our new approach comprises a single layer of a reactive nanocomposite, made of intermixed metal nanoparticles, instead of multilayer systems. In this study we will present the development of the reactive nanocomposite from choice of materials through processing steps, handling and application methods and eventually the results of our experiments upon the reactivity of the nanocomposites and the feasibility for bonding applications.
Enzymatic biosensor based on immobilized carbon nanotube transducer
Andreja Petrovic, Master Student, University of Ljubljana, Faculty of Chemistry and Chemical Technology
Although enzyme-based electro-chemical bio-sensors show significant potential towards the construction of a sensitive and selective sensor, a direct quantitative detection of the enzyme’s catalytic activity still remains challenging. Distinct properties of the enzyme are required as well as an electrode in order to enhance the direct electron transfer (DET) between the enzyme’s catalytic active site and the electrode.
Enzymes that contribute to these requirements are the cytochrome P450 enzymes (CYPs) that comprise for about 80% of the phase-I drug-metabolizing enzymes in the human liver. The isoenzyme cytochrome P450 2D6 (CYP2D6) is responsible for the metabolisation of 25% of all clinically prescribed drugs; therefore the interaction potential of xenobiotics with this isoenzyme is of utmost importance. Due to the fact that the CYP catalysed metabolisation reactions are electron dependent oxidative processes, CYPs are suitable candidates for the construction of a small-scale bio-sensor.
In our study, a screen printed working electrode with an additional carbon nanotube (CNT) layer was used for the immobilisation of the CYP2D6 enzyme. Two fundamentally different immobilisation techniques were investigated: (i) non-covalent immobilisation and (ii) covalent immobilisation, where either physical interactions or direct chemical bonds were exploited for the stable and electronically efficient connection between the enzymes and CNT electrode. The immobilisation was characterised by testing the activity of the enzymes through enzymatic demethylation of a model substrate, i.e. dextromethorphan, before and after an intensive wash of the working electrode. The concentration of the substrate and its product, i.e. dextrorphan, were determined using a high-performance liquid chromatography (HPLC). The stability, selectivity and sensitivity of the biosensor were further evaluated using a cyclic-voltammetrical processing of the induced signal.
A Review on Sensing technologies, Microfabrication and Process development with Cleanroom focus
Mohssen Moridi, MST Area manager, CTR
Mohssen Moridi obtained his master’s degree in micro engineering from École Polytechnique Fédérale de Lausanne (Switzerland), where he also received his PhD in microsystems, in 2005 and 2011, respectively. After a postdoctoral period at EPFL, in 2012 he joined the Microcity research centre in Neuchatel (Switzerland) as a senior scientist to supervise and work on several projects to develop new MEMS sensors in collaboration with industrial partners and academic institutes. He worked on developing different kind of sensors such as optical detectors, magnetic sensors, integrated silicon amorphous photodiode detectors, ASIC post processing sensing devices, biomedical devices, microfluidic, hybrid and Lab-on-a-chip sensors. His more than 10 years of working experience with microsystem technology and cleanrooms gives him a broad knowledge and expertise with many sensing technologies, microfabrication, process development, and device characterization. Recently he joined CTR as the head of the Microsystems Technologies department.
Scanning Transmission Electron Microscopy: Applications in Materials Science
Prof. Dr. Miran Čeh, Department for Nanostructured Materials, Centre for Electron Microscopy and Microanalysis, Jožef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia
Various Scanning Transmission Electron Microscopy (STEM) imaging techniques (ADF, HAADF, ABF) have become extremely useful for materials characterization at the nano- and atomic scale, particularly due to recent developments in the correction of spherical aberrations of the (S)TEMs microscope lenses. The main principle underpinning these imaging techniques is that the detectors are designed in such a way that they mostly collect high-angle scattered electrons, thus minimizing the contribution of elastically scattered electrons to the image. As a consequence, the intensity of the atom columns can be correlated to the chemical composition, or in case of annular bright-field STEM imaging, the light elements can be observed. This lecture will present an overview on the basic principles of STEM imaging techniques. The results of qualitative and quantitative STEM imaging at the nano- and atomic scale will be presented and commented on for various oxide ceramic materials.
Characterization of a sub-wavelength waveguide sensor
Franz Josef Maier, TU-Wien, Institute of Applied Physics
Since CO2 has gotten a lot of attention in the past (climate change for example), there is a lot of interest in reducing the size and cost of CO2 sensors and subsequently allow a mass production of these sensors. As semiconductor technology allows for a realization of these requirements, a project was initiated by Infineon. A team at the JKU-Linz, led by Prof. Jakoby, made the theoretical design of this sensor. The working principle of these sensors is the absorbance of the evanescent field of a sub-wavelength waveguide, as I will explain in the talk. Part of my thesis was the design of a test bench used for an optical and electrical characterization of the waveguides and measurements of the absorbance of CO2 and Chloroform with the waveguide sensors. I will also talk about advantages and disadvantages of the waveguiding technology and give a future outlook on the project.
Extreme Satellite Miniaturization, the experience of Microspace with POPSAT and ATHENOXAT
Dr. Giulio Manzoni, Microspace Communications Cooperation, Managing Director
Spacecraft miniaturization is a popular trend since over a decade and has grown from University exercises to fully performing satellites with commercial value. Challenges and successes will be discussed in particular for the application on remote sensing. The results of the two satellites POPSAT and ATHENOXAT, developed to demonstrate micropropulsion attitude control, formation flight capability, day and night vision on medium-high resolution will be presented.
Vehicle collision detection using a “locust eye algorithm” and vision in dim-light conditions.
Assoz. Prof. Dr. Manfred Hartbauer, Institute of Zoology, Karl-Franzens-Universität Graz
Extracting the information about impending collisions from the visual scene viewed from the ego-perspective of a fast moving agent is a challenging task that is solved in an efficient way in locusts flying in swarms of million individuals. Rapid luminance changes in adjacent receptors lead to the excitation of motion-sensitive layers that are connected to neurons selectively responding to impending collisions. This was simulated in a bionic computer model where the collision risk is extracted from traffic movies exhibiting a low spatial resolution. This method relies on relative object expansion and is therefore independent of distance measurements and object recognition. Additionally, the calculation of directional motion information can be used to compute the direction and force of evasive steering. Camera shaking and quickly approaching ground shadows are partially compensated. After parameter tuning, simulation results show that this method reliably indicates impending collisions and, if possible, an evasive steering direction using various crash car movies as input.
The problem for camera sensors used in dark conditions comes with noise that is amplified after application of common image enhancement procedures. Therefore, the second part of my talk addresses the night vision capabilities of the solitary bee Megalopta genalis (Greiner et al. 2004). The way eyes of this bee cumulate photons by simultaneously maintaining spatial and temporal resolution already inspired the development of innovative night vision cameras. Recently, I developed an iterative procedure that increases grey value saturation by simultaneously reducing sensor noise. Image blur is prevented by 'adaptive spatial averaging'. Additionally, temporal summation of grey values using static images as input was made possible by modelling saccadic eye movements. In both computer models most processing steps can be performed on the sensor thus computational demands can be minimized.
FEM Simulation of the Thermo-Mechanical Behaviour of Si-Metal Composites
Wasif Kahn, M. Sc. Student, Computational Mechanics, Universität Duisburg Essen
During the manufacturing, thin slender Si wafers are coated with thin metal layers at high temperatures. When this composite is cooled down to room temperature, stresses are developed due to different thermal expansion coefficients of silicon and metal, leading to the deformation of the wafer. The aim of this master thesis is to develop and validate the appropriate modelling approaches for this classical thin-film-on-substrate problem for thin slender Si wafers using FEA program ANSYS.
Stoney's approach is modified for circular plates with anisotropic substrates subjected to thermal mismatch for the purpose of theoretical calculations. Further, considering the limitations of Stoney's approach, an analytical approach is developed based upon large deformation theory to predict the behaviour of thin slender wafers. In order to calculate the curvature from FE results, two analytical approaches based upon least square method and second order differential approximations are developed in program MATHEMATICA.
The problem is solved in two subsequent steps. In the first step, a moderately thick plate is analysed for isotropic and anisotropic substrates. Several modelling approaches based upon varying element types, element sizes, contact formulations and number of timesteps are examined in this step. In the second step, this study is extended to the thin slender wafers and studied in different regimes of in-plane film stress - curvature relationships. Bifurcation phenomenon, an important characteristic of geometrical nonlinearity is also examined.
The limitations of Stoney's approach for large deformations are mentioned. Analytical approach based upon large deformation theory is found to be serving a strong base for the purpose of comparison of FE results. The use of layered shell elements for anisotropy, large deformations and optimum calculation efforts is also examined.