Dresden 2003 – scientific programme

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DY: Dynamik und Statistische Physik

DY 46: Poster

DY 46.13: Poster

Thursday, March 27, 2003, 15:30–18:00, P1

Hydrodynamic coupling of two rotating spheres — •Michael Reichert and Holger Stark — Universität Konstanz, Fachbereich Physik, D-78457 Konstanz, Germany

Colloids are widely considered as models for atomic systems. However, there is one feature specific to colloidal dispersions, which distinguishes them from atomic systems: hydrodynamic interactions. These only occur when particles move relative to each other. In recent years, microrheological experiments [1,2] have been performed where the correlation functions of optically trapped particles are measured to determine properties of the surrounding fluid.

In our presentation, we study the hydrodynamic coupling of a pair of spheres due to their translational and rotational motions. We trap the positions and orientations of the particles by harmonic potentials, which mimic optical tweezers, and determine the eigenmodes of such a system. From this analysis, one can directly calculate the correlation functions of the positions and orientations when the particles undergo thermal fluctuations. We present in detail the time- and distance-dependent behaviour of these correlations, which can be measured in experiments.

[1] J.-C. Meiners, S. R. Quake, Phys. Rev. Lett. 82 (1999), 2211

[2] S. Henderson, S. Mitchell, P. Bartlett, Phys. Rev. E 64 (2001), 061403