Determining phoretic mobilities with Onsager's reciprocal relations: electro- and thermophoresis revisited

TL;DR

This paper presents a hydrodynamic reciprocal approach to derive general expressions for electrophoretic and thermophoretic mobilities of weakly charged colloids, extending previous models by incorporating various boundary conditions.

Contribution

It introduces a unified framework based on Onsager's reciprocal relations to calculate colloid mobilities, accounting for different boundary conditions and interaction ranges.

Findings

Derived general expressions for electrophoretic and thermophoretic mobilities.

Extended existing models to include diverse hydrodynamic boundary conditions.

Provided a theoretical basis for understanding phoretic motion in electrolyte solutions.

Abstract

We use a hydrodynamic reciprocal approach to phoretic motion to derive general expressions for the electrophoretic and thermophoretic mobility of weakly charged colloids in aqueous electrolyte solutions. Our approach shows that phoretic motion can be understood in terms of the interfacial transport of thermodynamic excess quantities that arises when a colloid is kept stationary inside a bulk fluid flow. The obtained expressions for the mobilities are extensions of previously known results as they can account for different hydrodynamic boundary conditions at the colloidal surface, irrespective of how the colloid-fluid interaction range compares to the colloidal radius.