by Prof. Dr. rer. nat. habil. Ursula van Rienen, Lehrstuhl Theoretische Elektrotechnik, Universität Rostock
06.09.2018, 17:00 h, TF, Aquarium
Deep Brain Stimulation (DBS) is a widely used neuronal stimulation therapy for movement disorders like Parkinson’s disease and dystonias. Simulation studies can help for a deeper understanding of this therapy and, in future, for a patient-specific therapy planning aiming to prevent side effects as well. On the other hand, simulations can help e.g. to optimally select stimulation parameters in animal models.
The dielectric properties of biological tissue are based on experimental data and are subject to uncertainty, which arises from difficulties associated with the measuring process such as electrode polarisation at low frequencies, changes in the conditions of the tissue samples post mortem, and inter-individual variations. Based on the current state of measurement techniques for the dielectric properties of biological tissue, it can be assumed that uncertainty in these measurements and the resulting tissue properties will be a non-negligible factor, which has to be considered in computational models of bio-electrical applications.
In this contribution, we will introduce to the simulation pipeline to compute the Volume of Tissue Activated for a human model including uncertainty quantification and show some exemplary simulation results.
by Dr. Giselher Herzer, Vacuumschmelze GmbH & Co. KG, Hanau
10.07.2018, 17:00 h, TF, Aquarium
Retailers lose billions of Euros per year to shoplifters. Department store detectives and video cameras are therefore increasingly being assisted by electronic article surveillance (EAS). Hundred thousands of such systems are meanwhile installed and millions of disposable security labels are being produced on a daily base. Basically all EAS-systems operate on the same principle: Articles are affixed with security labels which, if not deactivated at the cash register, respond to electromagnetic fields generated from pedestals at the store's exits. The response is picked up by an antenna in the pedestals, thereby triggering an alarm. Today’s security labels are disposable items which are also used to secure inexpensive articles. Moreover, EAS labels are increasingly integrated directly into products or packaging during the manufacturing or packaging process. One major requirement therefore is that the labels are small and cheap. Further requirements are that the labels are reliably detectable and deactivatable and, as one of the major requests, that they cause no false alarms.
One of the most wide-spread EAS systems is based on magnetoelastic sensors which represent the latest and most sophisticated technology. The sensor element is a short magnetostrictive amorphous alloy ribbon which is housed in a small cavity such that it can vibrate freely. It is excited by magnetic field pulses to longitudinal, resonant vibrations. Once an exciting tone burst is over, the mechanical vibrations ring down exponentially over a time period of several milliseconds, hereby inducing a characteristic voltage in the receiver antenna while the exciting field is off. The detection electronics traces these echo voltages and triggers alarm if it recognizes the typical characteristics (like resonant frequency and ring-down time) of the resonator.
The talk surveys the physics behind magnetoelastic EAS labels and illustrates how to customize the sensor material by appropriate alloy design and thermal treatment.
by Prof. Dr. Nian Sun, Northeastern University, Boston, USA
18.06.2018, 17:15 h, TF, Aquarium
The coexistence of electric polarization and magnetization in multiferroic materials provides great opportunities for realizing magnetoelectric coupling, including electric field control of magnetism, or vice versa, through a strain mediated magnetoelectric coupling in layered magnetic/ferroelectric multiferroic heterostructures [1-9]. Strong magnetoelectric coupling has been the enabling factor for different multiferroic devices, which however has been elusive, particularly at RF/microwave frequencies. In this presentation, I will cover the most recent progress on new integrated magnetoelectric materials, magnetoelectric NEMS (nanoelectromechanical system) based sensors and antennas. Specifically, we will introduce magnetoelectric multiferroic materials, and their applications in different devices, including: (1) novel ultra-compact RF NEMS acoustic magnetoelectric antennas immune from ground plane effect with < l0/100 in size, self-biased operation and potentially 1~2% voltage tunable operation frequency; and (2) ultra-sensitive RF NEMS magnetoelectric magnetometers with ultra-low noise of ~1pT/Hz1/2 at 10 Hz for DC and AC magnetic fields sensing. These novel magnetoelectric devices show great promise for applications in compact, lightweight and power efficient sensors and sensing systems, ultra-compact antennas and for radars, communication systems, biomedical devices, IoT, etc.
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by Dr. Andreas Winkler, Leibniz Institut für Festkörper- und Werkstoffforschung Dresden, Germany
14.06.2018, 17:00 h, TF, Aquarium
Since several decades, surface acoustic waves have been excited via interdigital transducers on piezoelectric chips with high accuracy and reproducibility. The first generation of such technological devices, namely radio-frequency filter elements including transversal filters and resonators, became a substantial piece for the operation of any wireless electronic device. In this field, progress is mainly related to migration-resistant materials, improved lithography techniques and advanced transducer design for increased frequency operation as well as to realize transfer functions of higher complexity. In addition, very promising SAW applications in the fields of sensors and actuators have been demonstrated in labs around the world within the last 20 years. These already include wireless, self-sufficient sensors and ID-tags, lab-on-a-chip devices for fundamental microfluidic tasks and on-chip aerosol generators. In contrast to their pure electro-mechanic ancestors, these devices interact with gases or complex (bio-)fluids or have to resist harsh environmental conditions. Thus, they require a completely different and a comprehensive scientific approach, which currently hinders their commercialization. In this presentation, promising applications of SAW devices are highlighted together with the most critical requirements related to the materials involved, energy efficiency issues and technology concepts.
by Prof. Dr. Richard Fu, University of Northumbria at Newcastle, UK
28.05.2018, 17:15 h, TF, Aquarium
Thin film acoustic wave devices especially surface acoustic waves (SAW) have been used for sample preparation (sorting, separating, mixing, nebulization and dispensing) as well as bio-sensing. This talk will focus on our recent work of flexible and wearable thin film acoustic wave lab-on-chip (mainly using ZnO and AlN films on flexible substrates) for acoustic wave based microfluidic applications. We report theoretical and experimental studies of the evolution, hybridization and decoupling of wave modes in the flexible acoustic wave devices, as well as their vibration patterns. thus providing a guide for different microfluidic applications. Thin film based flexible SAW devices have the potential to be integrated with other microfluidic and sensing technology on flexible substrates including CMOS integrated circuits to make novel lab-on-chip for bio-detection for wearable and flexible applications. SAW devices on commercial polymer and aluminum foils have been fabricated and various microfluidic functions, such as mixing, pumping, jetting have been demonstrated with bent and deformed acoustic wave devices.
Brain Signal Acquisition with Miniaturized Electronic Systems for the Investigation of Local Neural Networks
by Prof. Dr. Andreas Bahr, CAU Kiel, inaugural lecture
26.04.2018, 17:15 h, TF, Aquarium
In neuroscience research the development of the brain and the treatment of diseases like certain forms of epilepsy are analyzed with genetic mouse disease models. For the special case of the recording from neonatal mice (2-3 cm, 3-5 g) an implantable system has been developed, that enables chronic recordings. To achieve this, an application specific integrated circuit (ASIC) has been developed in an advanced 130 nm CMOS technology. Moreover, an implant and a recording system for live view of neural data have been presented. The functionality of the integrated circuit and the suitability of the implant system have been confirmed with in-vivo experiments with adult and 12 days old mice.
by Dr. Tilmann Sander-Thömmes, Physikalisch-Technische Bundesanstalt, Berlin, Germany
23.04.2018, 17:15 h, TF, Aquarium
Biomagnetische Sensor- und Auswertesysteme - Fortschritt durch einen modularen Ansatz
In the field of biomagnetism the application of mathematical algorithms has been as important as the hardware itself. Traditionally, the hardware (the sensor Array) was based on superconducting quantum interference devices (SQUIDs) and operated for decades without large modifications. In contrast to that the range of relevant mathematical algorithms increased at a steady pace. This was driven by factors such as an ever increasing PC based computing power, new physiological insights motivating the application of existing algorithms, and the development of new algorithms to test biophysical models among others.
After around three decades of SQUID based Hardware, now new magnetic field sensors with the potential to replace or complement SQUIDs are available or under development. The opportunity for new sensors is the consequence of clinical challenges unsolved by state-of-the art SQUID based systems and due to new technology allowing alternative quantum physics based sensors in a small sized housing. These new sensors often have extra capabilities compared with SQUIDs and naturally some disadvantages. I will illustrate the modular approach using the example of optically pumped magnetometers and the signal processing toolbox FieldTrip.
Tilmann Sander-Thömmes studied Physics at University of Freiburg and ETH Zürich and graduated there in 1992. He continued to obtain a PhD in solid-state physics at Imperial College in London. Following two post-docs in Berlin he has been working at Physikalisch-Technische Bundesanstalt since 2000 in the laboratory for Biosignals. Since 1998 he is involved with measuring and analysing magnetic brain signals. He is an expert in magnetoencephalography using both SQUIDs and more recently optically pumped magnetometers.
by Prof. Dr. Jörg Wrachtrup, Institute for Quantum Science and Technology, University of Stuttgart, Germany
19.04.2018, 17:00 h, TF, Aquarium
The accuracy of measurements is limited by quantum mechanics. Ingenious demonstrations, like measuring gravitational fields or time have explored accuracy limits and reached fundamental obstructions. Yet, precision measurements so far are restricted to dedicated environmental conditions essentially excluding “every day” applications. In the talk I will discuss spin quantum sensors comprising a single or multiple electron spins. With such a system we measure a variety of quantities including electric and magnetic fields, temperature, and force under ambient conditions. We use nuclear spins to enhance the measurement accuracy of the electron spin e.g. via quantum error correction or as ancillary quantum bits as memory or for quantum Fourier transformation [1-3]. I will present a variety of applications ranging from quantum simulations to imaging of cellular structures. I will emphasize the engineering challenges of these sensors and discuss their use to e.g. measure biomagnetic fields.
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by Prof. Dr. Oskar Paris
08.02.2018, 17:00 h, TF, Aquarium
Advanced functional materials for sensing, actuation, or energy storage are often based on highly porous materials with large surface area. They are typically organized at several length scales and their functionality critically depends on the pore geometry at the nanometre and sub-nanometre scale. The quantification of the interaction of the internal solid surface with guest atoms, -molecules, or -ions calls for non-destructive, bulk-sensitive in-situ techniques. The lecture will discuss the potential of small-angle X-ray (SAXS) and neutron scattering (SANS) in this respect. My first example will deal with the interaction of fluid guest phases with the solid pore walls of nanoporous silica, leading to a fluid-pressure dependent, non-monotonous deformation of the material. By using tailor made materials with ordered mesopores, this deformation can be monitored via the pore lattice strain from in-situ SAXS or in-situ SANS. The structural origin for the macroscopic adsorption-induced mechanical deformation of complex systems such as macroscopic monoliths with hierarchical porosity , or nanoporous thin films on non-porous substrates  will be discussed, both systems being promising model systems for actuation devices. The second example deals with structural studies of aqueous electrolytes in nanoporous carbons as a function of an applied voltage. The results from such model supercapacitors demonstrate that in-situ SAXS from disordered carbon electrodes together with new ways of data analysis allow far-reaching interpretation of ion storage mechanisms and related predictions about optimum pore geometry . Moreover, electrodes based on ordered mesoporous carbons allow assessing electrosorption induced deformation of the carbon electrodes in-situ as a function of applied voltage .
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by Prof. Dr. Sebastiaan van Dijken
11.01.2018, 17:00 h, TF, Aquarium
Spintronic devices currently rely on magnetic switching or controlled motion of magnetic domain walls by an external magnetic field or electric current. Achieving the same degree of magnetic controllability using an electric field has potential advantages including low power consumption. Here, an approach to electrically control local magnetic properties will be discussed [1-5]. The method is based on recurrent strain transfer from regular ferroelastic stripe domains in a ferroelectric BaTiO3 substrate to magnetostrictive films (e.g. CoFe, CoFeB, and Fe). Dominance of the strain-induced magnetoelastic anisotropy in these heterostructures causes full imprinting of ferroelectric domain patterns into ferromagnetic films and strong pinning of magnetic domain walls onto ferroelectric boundaries [6,7]. Optical polarization microscopy measurements of the ferromagnetic and ferroelectric domain structures indicate that domain correlations and strong inter-ferroic domain wall pinning are maintained in an applied electric field. As a result, deterministic electric-field control over the formation and erasure of ferromagnetic domains [1-3] and reversible motion of magnetic domain walls [4,5] are obtained. In addition, regular modulations of magnetic anisotropy in strain-coupled multiferroic heterostructures provide a versatile platform for the excitation and manipulation of spin waves [8,9]. These findings open up new routes towards electric-field driven spintronics and magnonics.
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