Regensburg 2016 – wissenschaftliches Programm

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BP: Fachverband Biologische Physik

BP 39: Active Matter (Joint Session with DY)

BP 39.5: Vortrag

Mittwoch, 9. März 2016, 10:45–11:00, H46

Active Brownian particles at interfaces: An effective equilibrium approach — •René Wittmann and Joseph Brader — Departement für Physik, Universität Fribourg, 1700 Fribourg, Schweiz

Understanding self-organization in active Brownian systems is a subject of increasing theoretical interest. Recently, a microscopic equilibrium theory was developed from first principles [1], which accounts for the motility-induced phase separation (MIPS) observed in numerous experiments. This is achieved by mapping the active system onto an effective (static) interaction potential.

So far, experimental studies of active systems have focused on bulk properties. We apply our effective equilibrium theory [1] to inhomogeneous systems using density functional theory (DFT) with a simple perturbative treatment of the (effective) attractive interaction. In this case, the activity induces an effective external (wall) potential [2,3].

For a passively repulsive active fluid at a passively repulsive wall, the theory predicts motility-induced wetting as the MIPS transition is approached. For a Lennard-Jones interparticle potential the wall first dries with increasing activity, followed by a re-entrant wetting phenomenon. In a slit pore we observe motility-induced capillary condensation or evaporation, depending on the passive potential. These findings [3] constitute a compelling motivation to study such systems experimentally or using Brownian dynamics simulations.

[1] T. F. F. Farage, P. Krinninger and J. M. Brader, Phys. Rev. E 91, 042310 (2015). [2] A. Pototsky and H. Stark, Europhys. Lett. 98 50004 (2012). [3] R. Wittmann and J. M. Brader, in preparation.