Berlin 2015 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 33: P5: Microswimmers, Active Liquids

CPP 33.3: Poster

Tuesday, March 17, 2015, 14:00–16:00, Poster C

Active microrheology in colloidal soft-matter — •Robert Wulfert¹, Udo Seifert¹, and Thomas Speck² — ¹II. Institut für Theoretische Physik, Universität Stuttgart, Germany — ²Institut für Physik, Johannes Gutenberg-Universität Mainz, Germany

Tracking the microscopic motion of a driven colloidal probe through a complex host medium delivers valuable insight regarding the system’s dissipative behaviour in the non-linear response regime. The active forcing disturbs the equilibrium microstructure around the probe causing an excess of particles in front and a depopulated wake trailing it. This anisotropy in the pair-distribution corresponds to a frictional drag on the probe due to colloidal interactions, which can be interpreted in terms of an effective viscosity on the micron-scale. We calculate the pair-distribution function from the pair-Smoluchowski equation for hard-sphere colloids with additional long-range interactions. Furthermore, we discuss how the resulting velocity-force relations generalize in the case of dense and hence strongly interacting host suspensions and compare our results to Brownian dynamics simulations.