A Unified Description of Colloidal Thermophoresis

TL;DR

This paper develops a comprehensive theoretical framework for colloidal thermophoresis, clarifying the physical mechanisms and providing explicit expressions for transport coefficients, emphasizing the hydrodynamic nature of the phenomenon.

Contribution

It introduces a unified, thermodynamics-based description of colloidal thermophoresis that clarifies underlying mechanisms and generalizes previous models.

Findings

Derives an expression for interfacial force density driving thermophoresis.

Shows thermophoresis has a hydrodynamic origin, not purely thermodynamic.

Provides explicit relations for transport coefficients.

Abstract

We use the dynamic length and time scale separation in suspensions to formulate a general description of colloidal thermophoresis. Our approach allows an unambiguous definition of separate contributions to the colloidal flux and clarifies the physical mechanisms behind non-equilibrium motion of colloids. In particular, we derive an expression for the interfacial force density that drives single-particle thermophoresis in non-ideal fluids. The issuing relations for the transport coefficients explicitly show that interfacial thermophoresis has a hydrodynamic character that cannot be explained by a purely thermodynamic consideration. Our treatment generalises the results from other existing approaches, giving them a clear interpretation within the framework of non-equilibrium thermodynamics.