Eur. Phys. J. E (2018) 41: 7
https://doi.org/10.1140/epje/i2018-11610-3

Colloquium

A unified description of colloidal thermophoresis

¹ Cavendish Laboratory, University of Cambridge, CB3 0HE, Cambridge, UK
² Department of Chemistry, University of Cambridge, CB2 1EW, Cambridge, UK
³ Departament de Física de la Matèria Condensada, Universitat de Barcelona, C. Martí i Franquès 1, 08028, Barcelona, Spain
⁴ Institute of Complex Systems (UBICS), Universitat de Barcelona, Barcelona, Spain
⁵ CECAM Centre Européen de Calcul Atomique et Moléculaire, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015, Lausanne, Switzerland

^* e-mail: jb920@cam.ac.uk
^** e-mail: df246@cam.ac.uk
^*** e-mail: ee247@cam.ac.uk

Received: 29 June 2017
Accepted: 21 December 2017
Published online: 16 January 2018

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.