Dresden 2017 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 44: Aktive Matter I (joint session DY/BP/CPP, organized by DY)

CPP 44.3: Talk

Wednesday, March 22, 2017, 15:30–15:45, HÜL 186

Motility-Induced Phase-Separation of Microswimmers: Hydrodynamics and Phase-Equilibria — •Johannes Blaschke and Holger Stark — Institut für Theoretische Physik, Technische Universität Berlin, Hardenberg Str. 36, 10623 Berlin, Germany

Active motion of microorganisms and artificial microswimmers is relevant both to real world applications as well as for posing fundamental questions in non-equilibrium statistical physics. Microswimmers are often modelled as active Brownian particles, neglecting hydrodynamic interactions between them. However, real microswimmers, such as ciliated microorganisms, catalytic Janus particles, or active emulsion droplets, employ propulsion mechanisms reliant on hydrodynamics. Therefore, we use multi-particle collision dynamics to explore the influence of hydrodynamics on the collective behavior of spherical microswimmers in quasi-two-dimensional geometry [1].

A striking feature of the collective motion of microswimmers is that for sufficiently strong self-propulsion they phase-separate into dense clusters coexisting with a low-density gas phase. Here we examine the influence of hydrodynamic interactions on this motility-induced phase separation. The most striking difference with the phase diagram of active Brownian particles is that a larger mean density results in a lower density of the coexisting dilute phase, which is a clear signature of hydrodynamics. Furthermore, we find that pushers or pullers suppress phase separation by increasing the critical Péclet number.

[1] J. Blaschke, M. Maurer, K. Menon, A. Zöttl, and H. Stark, Soft Matter (2016), DOI:10.1039/C6SM02042A.