Fluctuating chemohydrodynamics and the stochastic motion of self-diffusiophoretic particles

TL;DR

This paper develops a thermodynamically consistent stochastic framework for modeling the motion of self-diffusiophoretic particles, incorporating fluctuations and mechanochemical couplings derived from fluctuating chemohydrodynamics.

Contribution

It introduces coupled Langevin equations based on fluctuating chemohydrodynamics that accurately describe active particle dynamics with thermodynamic consistency.

Findings

Langevin equations incorporate fluctuations and mechanochemical coupling.

Equations satisfy microreversibility and Onsager-Casimir relations.

Provides a thermodynamic basis for active particle motion analysis.

Abstract

The propulsion of active particles by self-diffusiophoresis is driven by asymmetric catalytic reactions on the particle surface that generate a mechanochemical coupling between the fluid velocity and the concentration fields of fuel and product in the surrounding solution. Because of thermal and molecular fluctuations in the solution, the motion of micrometric or submicrometric active particles is stochastic. Coupled Langevin equations describing the translation, rotation, and reaction of such active particles are deduced from fluctuating chemohydrodynamics and fluctuating boundary conditions at the interface between the fluid and the particle. These equations are consistent with microreversibility and the Onsager-Casimir reciprocal relations between affinities and currents, and provide a thermodynamically consistent basis for the investigation of the dynamics of active particles propelled by diffusiophoretic mechanisms.