Normal and lateral critical Casimir forces between colloids and patterned substrates

TL;DR

This paper investigates the critical Casimir forces between a colloid and a chemically patterned substrate, providing a universal scaling function and demonstrating the importance of geometrical details in experimental predictions.

Contribution

The study introduces a universal scaling function for critical Casimir forces involving patterned substrates and compares theoretical predictions with experimental data.

Findings

Critical Casimir forces are highly sensitive to substrate geometry.

Theoretical predictions accurately match experimental data when substrate patterns are considered.

Critical Casimir forces serve as a sensitive probe for surface patterning effects.

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, 208301 (2008)]. 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.