Critical Casimir forces in soft matter

TL;DR

This review discusses recent progress in understanding critical Casimir forces in soft matter, highlighting their controllability, influence on colloidal structures, and potential applications in micro-mechanical systems.

Contribution

It synthesizes recent theoretical, numerical, and experimental findings on critical Casimir forces, emphasizing their unique controllability and relevance for soft matter applications.

Findings

Critical Casimir forces can be reversibly controlled by temperature.

Surface treatments influence the attractive or repulsive nature of these forces.

They have potential applications in micro-mechanical systems.

Abstract

We review recent advances in the theoretical, numerical, and experimental studies of critical Casimir forces in soft matter, with particular emphasis on their relevance for the structures of colloidal suspensions and on their dynamics. Distinct from other interactions which act in soft matter, such as electrostatic and van der Waals forces, critical Casimir forces are effective interactions characterised by the possibility to control reversibly their strength via minute temperature changes, while their attractive or repulsive character is conveniently determined via surface treatments or by structuring the involved surfaces. These features make critical Casimir forces excellent candidates for controlling the equilibrium and dynamical properties of individual colloids or colloidal dispersions as well as for possible applications in micro-mechanical systems. In the past 25 years a number of theoretical and experimental studies have been devoted to investigate these forces primarily under thermal equilibrium conditions, while their dynamical and non-equilibrium behaviour is a largely unexplored subject open for future investigations.