PACK Fellowship Seminar on August 27, 2020
PACK Fellowship Seminar on July 30, 2020
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 [1], for applications like conductive silicone, energy materials and cell templates as well as the fabrication of aero hexagonal boron nitride [2] that can be employed in optics as "artificial solid fog".
[1] Nature Communications 8, 1215 (2017)
[2] Nature Communications 11, 1437 (2020)
PACK Fellowship Seminar on June 26, 2020
PACK Fellowship Seminar on May 19, 2020
Presentation Abstract:
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Magnetic shielding
by Dr. Allard Schnabel, Physikalisch-Technische Bundesanstalt (PTB) Berlin
13.02.2020, 17:00 h, TF, Seminar Room C-SR 1
Abstract
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.
Atomistically inspired origami
by Prof. Dr. Richard D. James, University of Minnesota
16.01.2020, 13:15 h, TF, Aquarium
Abstract
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.
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