Regensburg 2016 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 35: Active Matter (joint session DY/BP)

DY 35.11: Vortrag

Mittwoch, 9. März 2016, 12:30–12:45, H46

Pattern Formation and Clustering in Chemorepulsive Active Colloids — •Benno Liebchen¹, Davide Marenduzzo¹, Ignacio Pagonabarraga², and Michael E Cates³ — ¹SUPA, School of Physics and Astronomy, University of Edinburgh, Edinburgh EH9 3FD, United Kingdom — ²Departament de Fisica Fonamental, Universitat de Barcelona-Carrer Marti i Franques 1, 08028-Barcelona, Spain — ³DAMTP, Centre for Mathematical Sciences, University of Cambridge, Cambridge CB3 0WA, United Kingdom

Chemotaxis is the directed motion of particles in response to a gradient in a chemical signal. It allows micro-organisms, like bacteria, to find food and to escape from toxins. Some micro-organisms can produce the species to which they respond themselves and use chemotaxis for signalling. This can, in the case of chemoattraction where particles migrate up chemical gradients, induce a clustering-instability of the uniform state. This instability currently attracts renewed attention in artificial Janus colloids that swim by catalysing reactions in a chemical bath and show a similar signalling behaviour as micro-organisms.

Here, we demonstrate that also the previously underappreciated case of chemorepulsion (where particles migrate away from high chemical density) can induce clustering. The underlying instability may either rely on anisotropy in the chemical production at the particle surface or on delay effects. In contrast to chemoattractive clustering our chemorepulsive route predicts clusters of self-limiting size. This size increases with self-propulsion velocity which agrees qualitatively with recent experimental observations of dynamic clustering in active Janus colloids.