Seminars

The MRSEC holds seminars presenting research at the frontier of Bioinspired Soft Materials. The seminars are targeted towards grad students and other researchers in the field, although everyone is invited to attend. As the topic is highly interdisciplinary, seminars are designed to be accessible to a wide range of backgrounds. 

John Berezney, Dogic Lab Postdoc, Organizer MRSEC Seminars

Thursday, May 24, 2018
MRSEC Seminar: Amoeba-like Living Crystallites in Active Colloids
Paddy Royall, University of Bristol
Abstract: Many kinds of swimmers and self-propelled particles constitute physical models to describe collective behaviour and motility of a wide variety of living systems, such as the cytoskeleton, bacteria colonies. bird flocks and fish schools. Here study colloidal particles in an external DC electric field. Our experimental model system consists of quasi-two-dimensional arrays of electrically- driven particles and exhibits a rich phase behaviour. At low field strength, the particles undergo Brownian motion, yet electrohydrodynamic flows lead to long-ranged non-reciprocal? attractions and self-organisation into hexagonal crystallites. With an increase in field strength, we observe self-propulsion of the particles due to the electrohydrodynamic phenomenon known as Quincke rotation, i.e. the particles behave as active matter. This activity leads to surface melting resulting in an ordered phase of active matter where crystallites move and constantly change shape and collide with one another in a manner reminiscent of ameobae. At higher field strengths, we reveal an activity-mediated gas-solid transition, with an intermediate phase possessing orientational order. We combine our experiments with computer simulations, which reproduce the phase behaviour and moreover at higher field strengths than we reach in the experiments exhibit an activity-driven demixing to form a banded structure.
Abelson 229, 4PM

Thursday, May 31, 2018
MRSEC Seminar: Slimming down through frustration

Martin Lenz, Université Paris-Sud
Abstract: Controlling the self-assembly of supramolecular structures is vital for living cells, and a central challenge for engineering at the nano- and microscales. Nevertheless, even particles without optimized shapes can robustly form well-defined morphologies. This is the case in numerous medical conditions where normally soluble proteins aggregate into fibers. Beyond the diversity of molecular mechanisms involved, we propose that fibers generically arise from the aggregation of irregular particles with short-range interactions. Using minimal models of frustrated aggregating particles, we demonstrate robust fiber formation for a variety of particle shapes and aggregation conditions. Geometrical frustration plays a crucial role in this process, and accounts for the range of parameters in which fibers form as well as for their metastable, yet long-lived character.
Abelson 229, 4PM


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