Berlin 2005 – scientific programme

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DY: Dynamik und Statistische Physik

DY 34: Poster

DY 34.54: Poster

Monday, March 7, 2005, 15:30–18:00, Poster TU D

Depletion forces in colloidal systems — •Jules Mikhael, Laurent Helden, and Clemens Bechinger — 2. Physikalisches Institut, Universität Stuttgart, Pfaffenwaldring 57, 70550 Stuttgart, Germany.

The stability and phase behavior of colloidal suspensions containing particles of different size and shape is known to be strongly influenced by depletion forces. Various kinds of colloids as for example spheres, rod- and disc-like Particles or polymeres can serve as depletion agent. The depletion forces they induce can lead even in systems where all pair interactions are purely repulsive to attractive forces which may finally cause particle flocculation. Accordingly, the understanding of these forces is besides fundamental interest also essential for industrial processes. The technique of total internal reflection microscopy (TIRM) is capable to measure these weak depletion interactions with a force resolution in the order of 10 fN. Here we present direct measurements of depletion potentials between a sphere and a flat surface caused by various depletion agents.