Dresden 2009 – wissenschaftliches Programm
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DY: Fachverband Dynamik und Statistische Physik
DY 28: Pattern formation in colloidal and granular systems II
DY 28.3: Vortrag
Freitag, 27. März 2009, 10:45–11:00, HÜL 386
Critical Casimir forces between colloids and chemically patterned substrates — •Matthias Tröndle1,2, Svyatoslav Kondrat1,2, Andrea Gambassi1,2, Ludger Harnau1,2, and Siegfried Dietrich1,2 — 1Max-Planck-Institut für Metallforschung, Heisenbergstr. 3, D-70569 Stuttgart — 2Institut für Theoretische und Angewandte Physik Universität Stuttgart, Pfaffenwaldring 57, D-70569 Stuttgart
We study the effective critical Casimir forces acting on colloids immersed in a binary liquid mixture in the presence of a chemically structured substrate with laterally varying adsorption preference. Close to the critical point of the fluid, long-ranged correlations in the mixture cause pronounced normal and lateral critical Casimir forces between the colloids and the confining wall. The sign and the magnitude of these forces depend on the surface properties so that the colloids tend to align with the substrate pattern. This allows, for example, the formation of highly ordered colloidal monolayers. Recently, the measurement of critical Casimir interactions in such a system has been reported [F. Soyka, O. Zvyagolskaya, C. Hertlein, L. Helden, and C. Bechinger, PRL 101, 208301 (2008)]. Based on general renormalization group arguments, we calculate the universal scaling functions for the critical Casimir forces acting on a spherical colloid close to a chemically patterned substrate as well as for the corresponding interaction potential and compare our results with experimental data.