Effective interaction between a colloid and a soft interface near criticality

TL;DR

This study uses mean-field theory to derive the universal scaling function for the critical Casimir force on a colloid near a soft liquid-liquid interface close to criticality, highlighting differences from rigid wall scenarios.

Contribution

First to analyze critical Casimir forces involving a deformable soft interface near criticality using semi-analytical mean-field calculations.

Findings

Universal scaling function for the force was determined.

Interface deformation significantly affects the interaction potential.

Force behavior differs from that with rigid walls.

Abstract

Within mean-field theory we determine the universal scaling function for the effective force acting on a single colloid located near the interface between two coexisting liquid phases of a binary liquid mixture close to its critical consolute point. This is the first study of critical Casimir forces emerging from the confinement of a fluctuating medium by at least one soft interface, instead by rigid walls only as studied previously. For this specific system, our semi-analytical calculation illustrates that knowledge of the colloid-induced, deformed shape of the interface allows one to accurately describe the effective interaction potential between the colloid and the interface. Moreover, our analysis demonstrates that the critical Casimir force involving a deformable interface is accurately described by a universal scaling function, the shape of which differs from that one for rigid walls.