Hydrodynamics in bridging and aggregation of two colloidal particles in a near-critical binary mixture

TL;DR

This study explores how near-critical binary mixtures induce bridging and aggregation of colloidal particles through enhanced adsorption interactions, with dynamics governed by hydrodynamic flow and critical fluctuation effects.

Contribution

It demonstrates the role of temperature and particle movement in bridging and aggregation, incorporating critical fluctuation effects via a local functional theory.

Findings

Bridging significantly increases interparticle attraction.

Hydrodynamic flow influences the aggregation dynamics.

Critical fluctuations are incorporated into the interaction model.

Abstract

We investigate bridging and aggregation of two colloidal particles in a near-critical binary mixture when the fluid far from the particles is outside the coexistence (CX) curve and is rich in the component disfavored by the colloid surfaces. In such situations, the adsorption-induced interaction is enhanced, leading to bridging and aggregation of the particles. We realize bridging firstly by changing the temperature with a fixed interparticle separation and secondly by letting the two particles aggregate. The interparticle attractive force dramatically increases upon bridging. The dynamics is governed by hydrodynamic flow around the colloid surfaces. In aggregation, the adsorption layers move with the particles and squeezing occurs at narrow separation. We take into account the renormalization effect due to the critical fluctuations using the recent local functional theory [J. Chem. Phys. 136, 114704 (2012)].