Non-equilibrium Casimir-like Forces in Liquid Mixtures

TL;DR

This paper investigates how non-equilibrium concentration fluctuations in liquid mixtures under a temperature gradient induce Casimir-like forces on confining walls, driven by the Soret effect and concentration-dependent properties.

Contribution

It introduces the concept of non-equilibrium Casimir-like forces in liquid mixtures, highlighting the role of concentration fluctuations and the Soret effect in force generation.

Findings

Fluctuation-induced forces are proportional to the square of the Soret coefficient.

These forces are present near thermally conducting walls due to concentration fluctuations.

The magnitude relates to the concentration dependence of heat and mixing volume.

Abstract

In this Letter we consider a liquid mixture confined between two thermally conducting walls subjected to a stationary temperature gradient. While in a one-component liquid non-equilibrium fluctuation forces appear inside the liquid layer only, non-equilibrium fluctuations in a mixture induce a Casimir-like force on the walls. The physical reason is that the temperature gradient induces large concentration fluctuations through the Soret effect. Unlike temperature fluctuations, non-equilibrium concentration fluctuations are also present near a perfectly thermally conducting wall. The magnitude of the fluctuation-induced Casimir force is proportional to the square of the Soret coefficient and is related to the concentration dependence of the heat and volume of mixing.