Fluctuation interactions of colloidal particles

TL;DR

This paper investigates multiple mechanisms of attraction between like-charged colloidal particles at distances beyond the Debye length, highlighting the roles of van der Waals forces, fluctuation-mediated effects, and fluid density fluctuations.

Contribution

It identifies and analyzes three distinct attraction mechanisms in colloidal systems, including a newly emphasized fluctuation-mediated interaction influenced by fluid density.

Findings

Fluctuation-mediated attraction can be significant at large distances.

Uncharged particles with large Debye length exhibit the strongest attraction.

Thermal fluctuations of fluid density contribute to colloidal interactions.

Abstract

For like charged colloidal particles two mechanisms of attraction between them survive when the interparticle distance is larger than the Debye screening length. One of them is the conventional van der Waals attraction and the second one is the attraction mechanism mediated by thermal fluctuations of particle positions. The latter is related to an effective variable mass (Euler mass) of the particle produced by a fluid motion. The most stronger attraction potential (up to the value of temperature T) corresponds to a situation of uncharged particles and a relatively large Debye screening length. In this case the third mechanism of attraction enters the game. It is mediated by thermal fluctuations of a fluid density.