When measuring small magnetic fields as they appear in medical or biological applications, both, very small and very large signal amplitudes are observed at the same time. Small amplitudes stem, e.g., from human sources such as the human heart (magnetocardiography) or brain (magnetoencephalography). Low frequency signals (0.5 to 40 Hz) can be measured here with peak amplitudes of about 100 pT (heart) or even less than 1 pT (brain). Superposed to these small signals are usually large signal components that stem either from artificial sources, such as excitation signals utilized for modulation techniques, or from natural sources such as the magnetic field of the earth. Creating digital signals that can be used for detailed (medical) analyses is an interesting challenge for both, material scientists and engineers. Methods for improving the signal quality (mainly in terms of signal-to-noise ratio) can be grouped into analog and digital approaches, indicating whether they are performed prior or after the analog-to-digital (AD) conversion.
After the AD conversion so-called reference sensors can be used for recording signals that show a strong correlation with the disturbing but not with the desired signal component. Again, adaptive filtering techniques can be used to enhance the signal quality. However, such approaches are only successful if the analog amplifier followed by the AD converter are not saturated. Furthermore, often magnetoelectic sensors can be read out in a multitude of modes. This allows for adaptive combination of the individual signals, leading to improved robustness and better signal-to-noise ratio. In addition, several sensors can be combined and postprocessing such as digital noise suppression can be applied finally.
As a consequence, more “ingredients” than just the sensor are required for an entire sensor system. This leads to very interesting multidisciplinary research approaches. From sensors to sensor systems: it’s a rocky road.
Short CV of Gerhard Schmidt:
Gerhard Schmidt received the Dipl.Ing. degree in 1996 and the Dr.Ing. degree in 2001, both from Darmstadt, University of Technology, Germany. After his Ph.D., he worked in the research groups of the acoustic signal processing departments at Harman/Becker Automotive Systems and at SVOX, both in Ulm, Germany. Parallel to his time at SVOX he was a part-time professor at Darmstadt, University of Technology. Since 2010 he has been a full professor at Kiel University, Germany. His main research interests include adaptive methods for audio, SONAR, and medical signal processing.
by Asimina Kiourti, Ohio State University
10.12.2020, 16:00 h, Online Meeting
Rapid advances in bio-electromagnetics and materials are opening new and unexplored opportunities in body area sensing. This talk will discuss next-generation wearables and implants that break the state-of the-art boundaries in terms of seamlessness, capabilities, and performance. Focus will be on research efforts carried out in our group towards: a) functionalized garments that monitor body motion in real-world settings, b) wearable antennas for into-body radiation with unprecedented bandwidth and efficiency, c) portable sensors for capturing the naturally emanated magnetic fields by the human body as a predictor of abnormalities, and d) wireless and batteryless implants for deep-brain sensing. Enabling technologies will also be discussed, with a special focus on embroidered e-textiles. Flexibility and mechanical/thermal robustness associated with such conductive surfaces makes them highly attractive for numerous applications besides garments (e.g., efficient antenna folding and packaging; reconfigurable antenna surfaces; conformal airborne antennas). Our ultimate vision entails unobtrusive wearables and implants employed “in-the-wild” for applications as diverse as healthcare, sports, defense, space, emergency, consumer electronics, and beyond.
Thin film technology has pushed fascinating break through applications like microchip fabrication, medical technology or anti-reflection coatings. The presentation seeks to introduce the idea to bring the 2D thin film technology into 3D: Rolling up a thin film of nanoscopic thickness into a tube with a few micrometers in diameter, that is in space interconnected after a few tens of micrometers with other tubes pointing in different directions, will give you a relatively robust 3D tube network but with a weight in the scale of the ambient air and unusual physical properties. The talk will show that a simple sacrificial template approach can be used to realize these "aero structures". Properties of this class of materials will be illustrated but not limited to aero carbon structures from graphene or carbon nanotubes , for applications like conductive silicone, energy materials and cell templates as well as the fabrication of aero hexagonal boron nitride  that can be employed in optics as "artificial solid fog".
 Nature Communications 8, 1215 (2017)
 Nature Communications 11, 1437 (2020)
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by Dr. Allard Schnabel, Physikalisch-Technische Bundesanstalt (PTB) Berlin
13.02.2020, 17:00 h, TF, Seminar Room C-SR 1
Environments where the magnetic field is far below the earth magnetic field of 50 µT are a prerequisite for many modern precision experiments. Active magnetic field compensation with coil systems can reduce the external fields by up to two orders of magnitude. Passive magnetic shielding enclosures out of highly permeable material (µr >> 1) can provide volumes of up to 1 m3 with less than 1 nT static magnetic field. In combination with very sensitive magnetic field detectors like SQUIDs and OPMs, numerous basic physics experiments as well as biological studies have been carried out. In the past the driving force for the development of magnetically shielded rooms was brain research due to the spatial and temporal resolution of the neuronal activity. Today the strongest requirements are from basic physics experiments e.g. the search for a finite electric dipole moment of the neutron. These experiments need a homogeneous field of a few µT which should not change by more than 10 fT within 100 s.
Starting from the basic principles of magnetic shielding, commercially available shields will be discussed before the limits of the strongest existing magnetically shielded rooms, like BMSR-2 at PTB, are presented. In praxis, a larger shielding factor is associated with several restrictions which limit the usage of such shields. The demagnetization process (degaussing), necessary to achieve a low static magnetic field inside the shield, will be discussed in detail. It will also be explained why an “equilibration” of the shielding material is needed to obtain a field stable in time when an additional magnetic field is switched on or used inside the chamber.
by Prof. Dr. Richard D. James, University of Minnesota
16.01.2020, 13:15 h, TF, Aquarium
World population is growing approximately linearly at about 80 million per year. As time goes by, there is necessarily less space per person. Perhaps this is why the scientific community seems to be obsessed with folding things.
We present a mathematical approach to “rigid folding” inspired by the way atomistic structures form naturally. Their characteristic features in molecular science imply desirable features for macroscopic structures, especially 4D structures that deform.
Origami structures, in turn, suggest an unusual way to look at the Periodic Table.