Regensburg 2013 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 20: Poster: Colloids and Complex Liquids

CPP 20.26: Poster

Dienstag, 12. März 2013, 18:15–20:15, Poster C

Clustering and chemotactic collapse in a system of self-phoretic active particles — •Oliver Pohl and Holger Stark — Institut für Theoretische Physik, Technische Universität Berlin, D-10623 Berlin, Germany

Recent experiments of active colloids show a coexistence of single particles and clusters [1]. In such a "hot-cluster state" the clusters are themselves active and their sizes vary in time. In our model we separate two phoretic effects where the first accounts for activity and the second for interactions between the particles. Each colloid produces a gradient of a chemical which generates phoretic motion of nearby colloids; similar to bacteria moving along gradients of chemicals.

A hot-cluster state is reproduced which, depending on two parameters controlling interaction and activity, may exhibit a collapse to a single-cluster state. Such a collapse as well as the hot-cluster state have experimentally been observed in colonies of self-propelling bacteria [2,3]. The hot-cluster state is characterized by a power-law cluster distribution. Using a theory for nucleation and growth of clusters, we explain how clustering initiated by chemotaxis may be distinguished from clustering of particles with purely steric interactions.

[1] I. Theurkauff, C. Cottin-Bizonne, J. Palacci, C. Ybert, and L. Bocquet, Phys. Rev. Lett. 108, 268303 (2012).

[2] F. Peruani, J. Starrus, V. Jakovljevic, L. Søgaard-Andersen, A. Deutsch, and M. Bär, Phys. Rev. Lett. 108, 098102 (2012).

[3] E. Budrene, and H. Berg, Nature 349, 630 (1991).