Nonequilibrium Casimir-like Forces in Liquid Mixtures.

Area of Science:

• Thermodynamics
• Fluid Dynamics
• Soft Matter Physics

Background:

• Non-equilibrium fluctuations in liquids can generate forces.
• The Soret effect describes concentration changes due to temperature gradients in mixtures.
• Casimir forces typically arise from quantum fluctuations.

Purpose of the Study:

• To investigate non-equilibrium fluctuation forces in liquid mixtures confined by walls.
• To analyze the induction of a Casimir-like force by a temperature gradient.
• To understand the role of the Soret effect in generating these forces.

Main Methods:

• Theoretical analysis of a liquid mixture confined between two walls.
• Subjecting the system to a stationary temperature gradient.
• Investigating non-equilibrium concentration fluctuations and their impact.

Main Results:

• Non-equilibrium fluctuations in mixtures induce a Casimir-like force on walls.
• The Soret effect is the physical mechanism driving large concentration fluctuations.
• These fluctuations persist even near perfectly thermally conducting walls.

Conclusions:

• A novel Casimir-like force arises in liquid mixtures under a temperature gradient.
• The force magnitude is linked to the Soret coefficient and mixing thermodynamics.
• This phenomenon differs from forces observed in one-component liquids.