Light driven colloidal micro swimmers Seminar by Juliane Simmchen
from TU Dresden, Germany
In the last decade the generation of motion on the microscale has evolved into a fascinating field of modern science. We have learned to activate and control Janus particles in a regime dominated by low Reynolds numbers, where motion is not influenced by inertia. This implements several principles to take into account for the engineering of artificial microswimmers and often meant that toxic fuels had to be used to achieve propulsion. To move one step further towards possible applications in the environmental or biomedical field, we are now using light sensitive materials to explore new propulsion strategies.
Place: Soliden 3rd floor Time: 11 June 2019, 10:00
Reinforcement Learning in a Large Scale Photonic Network
Seminar by Daniel Brunner from FEMTO-ST Institute/Optics Department, CNRS & University Bourgogne Franche-Comté, Besançon Cedex, France
We experimentally create a neural network via a spatial light modulator, implementing connections between 2025 in parallel based on diffractive coupling. We numerically validate the scheme for at least 34.000 photonic neurons. Based on a digital micro-mirror array we demonstrate photonic reinforcement learning and predict a chaotic time-series via our optical neural network. The prediction error efficiently converges. Finally, we give insight based on the first investigation of effects to be encountered in neural networks physically implemented in analogue substrates.
Meltem Elitas is visiting from Sabanci University in Istanbul from 1st May until 28th June 2019.
Meltem Elitas is a faculty member at the Mechatronics Program at Sabanci University in Istanbul, Turkey. Her background is Electrical and Mechatronics Engineering; she obtained her doctorate from Bioengineerieng and Biotechnology Department at École Polytechnique Fédérale de Lausanne. She performed her postdoctoral studies at Yale University Biomedical Engineering Department. She has published more than 25 papers and conference proceedings in reputed journals. Her research interests are biomechatronics, cellular heterogeneity, cellular interactions, tumor microenvironment, live cell imaging and development of microfabricated tools for quantitative biology. She is visiting the Soft Matter Lab as part of her ongoing Marie Skłodowska-Curie project.
Sandra Heckel is visiting from the Technical University of Dresden from 26th March until 12th April 2019.
Sandra has a Bachelor degree in chemistry from TU Dresden and a Master degree in chemistry from TU Dresden and MIT, where she worked on a Master thesis about near-infrared bioimaging with semiconductor quantum dots.
In her PhD, she is working in the group of Juliane Simmchen on visible light-driven microswimmers and communication mechanisms among them.
If you would like to know more about Sandra Heckel and Juliane Simmchen’s research please visit their webpage.
Fast volumetric light-sheet microscopy
Seminar by Omar E. Olarte
from Universidad ECCI, Colombia (and ICFO, Barcelona, Spain)
Light sheet fluorescence microscopy (LSFM) is a convenient tool for bio-imaging as it efficiently collects the generated fluorescence while at the same time minimizes photobleaching. For these reasons LSFM, being based on an intrinsic 2D illumination strategy, has been put forward as an interesting candidate for fast volumetric imaging.
We report on a LSFM microscope, combined with the use of wavefront coding (WFC) techniques, for fast volumetric imaging. This provides intrinsic 3D imaging capabilities as it extends the depth of field (DOF) of the microscope. In addition, because of the extended DOF, the light sheet can be axially scanned at fast speeds. As only the light sheet is moved, fast 3D imaging can be achieved without the need of any sample or objective movement. Since typical light scanning devices can run at KHz rates, 3D volumetric acquisition speeds will only be limited by the reading speed of the camera or the required signal to noise ratio.
WFC works at the expenses of introducing a controlled aberration to the system which blurs the resulting images. Then it requires a final deconvolution step to recover the image sharpness that would impose a limitation on the application. Here we present computational tools to perform real-time deconvolution and visualization of the images obtained with WFC-LSFM. To speed up such deconvolution processes, a routine directly developed in a GPUs has been developed. We present preliminary results on realistic computer generated images showing that real-time deconvolution and visualization is possible.
Effective Drifts in Generalized Langevin Systems
Seminar by Soon Hoe Lim
from Nordita, Stockholm, Sweden, EU
Generalized Langevin equations (GLEs) are stochastic integro-differential equations commonly used as models in non-equilibrium statistical mechanics to describe the dynamics of a particle coupled to a heat bath. From modeling point of view, it is often desirable to derive effective mathematical models, in the form of stochastic differential equations (SDEs), to capture the essential dynamics of the systems. In this talk, we consider effective SDEs describing the behavior of a large class of generalized Langevin systems in the limits when natural time scales become very small. It turns out that additional drift terms, called noise-induced drifts, appear in the effective SDEs. We discuss recent progress on the phenomena of noise-induced drift in these systems. This is joint work with Jan Wehr and Maciej Lowenstein.
Place: Soliden 3rd floor Time: 12 December 2018, 13:00
Information Controlled Structure Formation in Artificial Microswimmer Systems General Physics Colloquium by Frank Cichos, University of Leipzig, Germany
Abstract: Self-organization is the generation of order out of local interactions in non-equilibrium. It is deeply connected to all fields of science from physics, chemistry to biology where functional living structures self-assemble and constantly evolve all based on physical interactions. The emergence of collective animal behavior, of society or language are the result of self-organization processes as well though they involve abstract interactions arising from sensory inputs, information processing, storage and feedback resulting in collective behaviors as found, for example, in crowds of people, flocks of birds, schools of fish or swarms of bacteria.
We introduce such information based interactions to the behavior of self-thermophoretic microswimmers. A real-time feedback of swimmer positions is used as the information to control the swimming direction and speed of other swimmers. The emerging structures reveal frustrated geometries due to confinement to two dimensions. They diffuse like passive clusters of colloids, but posses internal dynamical degrees of freedom that are determined by the feedback delay and the noise in the system. As the information processing in the feedback loops can be designed almost arbitrarily complex systems with mixed feedback delays and noise will give rise to new emergent dynamics of the self-organized structures. The presented control schemes further allow the integration of machine learning algorithms to introduce an adaptive behavior of swimmers.
Ripples in Thin Films
Seminar by Mazi Jalaal
from the Physics of Fluids laboratory
at the University of Twente, the Netherlands, EU
We present experimental observations of capillary ripples at the contact line of a droplet, spreading on a pre-wetted surface.
We use Digital Holographic Microscopy to measure the micro-scale undulation of the thin film. By raising the capillary number, the amplitude of the undulations increases at first and subsequently decreases.
At critical values of the capillary number, the ripples disappear. Using linear stability analysis, we further provide theoretical counterparts for the experimental observations, explaining the non-monotonic dependency on the capillary number
Place: PJ Lecture Hall Time: 9 October, 2018, 11:00
Cell differentiation and pattern formation in the transition to multicellularity: lessons from the microbial world Seminar by Mariana Benitez Keinrad
from the Laboratorio Nacional de Ciencias de la Sostenibilidad,
Universidad Nacional Autónoma de México (UNAM), Mexico.
Multicellular development occurs in plants, animals and other lineages, and involves the complex interaction among biochemical, physical and ecological factors. Our group has focused on the study of microbial multicellular organisms, which have been considered useful models to study the evolutionary transition to multicelullarity. I present some of our theoretical and experimental work, and discuss the physical and chemical processes that, in coordination with molecular regulatory networks, appear to be relevant for cell differentiation, patterning and morphogenesis in microbial aggregates.