Diffusion of colloidal particles in stationary and moving inhomogeneous environments

Stefan Egelhaaf
University of Düsseldorf, Germany

Abstract:
A colloidal particle dispersed in a liquid undergoes random motion. This motion is significantly changed if, e.g., the particle concentration is increased, obstacles are added or an external potential is imposed. We experimentally create external potentials using extended laser light fields, ranging from periodic patterns (laser fringes) to random patterns (speckle patterns) that might or might not depend on time. The dynamics of colloidal particles in these potential energy landscapes or in the presence of other particles are followed by video microscopy and quantitatively analysed. Diffusive as well as sub- and super-diffusive behaviour can be observed with the extent of the different regimes depending on the specific situation, such as the shape and modulation amplitude of the external potential but also the particle concentration and the composition of particle mixtures.