Normal and lateral critical Casimir forces between colloids and patterned substrates

Max-Planck-Institut für Metallforschung - Heisenbergstr. 3, D-70569 Stuttgart, Germany, EU Institut für Theoretische und Angewandte Physik, Universität Stuttgart - Pfaffenwaldring 57, D-70569 Stuttgart, Germany, EU

Received: 6 August 2009
Accepted: 28 October 2009

Abstract

We study the normal and lateral effective critical Casimir forces acting on a spherical colloid immersed in a critical binary solvent and close to a chemically structured substrate with alternating adsorption preference. We calculate the universal scaling function for the corresponding potential and compare our results with recent experimental data (Soyka F., Zvyagolskaya O., Hertlein C., Helden L. and Bechinger C., Phys. Rev. Lett.,101 (2008) 208301). The experimental potentials are properly captured by our predictions only by accounting for geometrical details of the substrate pattern for which, according to our theory, critical Casimir forces turn out to be a sensitive probe.