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DY: Fachverband Dynamik und Statistische Physik
DY 29: Particulate Matter: From microscopic interactions to collective motion (joint session DY/CPP)
DY 29.2: Vortrag
Dienstag, 13. März 2018, 14:15–14:30, EB 107
Microrheology in hard colloids with large tracers — •Antonio M. Puertas1, Francisco Orts2, Gloria Ortega2, and Ester M. Garzon2 — 1Dpt. of Applied Physics, Univ. of Almeria, Almeria, Spain — 2Dept. of Informatics, Univ. of Almeria, Agrifood Campus of Int. Excell., ceiA3, Almeria, Spain
Microrheology has become recently in a powerful technique to study the dynamics of a system in microscopic scales. A colloidal tracer is introduced in the host system, and its dynamics is monitored. When an external force acts on the tracer, the system goes out of equilibrium probing the linear regime for small forces, and entering the non-linear regime for large ones. A colloidal bath of hard spheres is probably the simplest example. Several theory models have been developed, tested by simulations, but typically these restrict to tracers of the same size as the bath particles.
Here, we present simulation results of the dynamics of a tracer pulled with a constant force in a colloidal bath. The tracer size, at, is larger than the bath particles, size a, up to at=5a. Important finite size effects appear, particularly for large tracers, which have been studied and compared with predictions from hydrodynamics for the bath. Due to the massive computational demand, the simulations were computed on a multiGPU cluster and a genetic algorithm was designed to optimize the performance. The dynamics of the tracer, providing the friction coefficient with the bath and the effects of the bath (density fluctuations, and strain field) are studied for small forces. The theoretical limit of an infinite tracer, a/at → 0, and small forces, is checked.