Local phase transitions in driven colloidal suspensions

TL;DR

This study explores how a moving tracer particle induces local phase changes in a colloidal suspension, revealing cavitation bubbles and bridges influenced by flow and boundaries, using theoretical and simulation methods.

Contribution

It introduces a combined theoretical and simulation approach to analyze local phase transitions caused by a driven tracer in colloids near the liquid binodal.

Findings

Formation of cavitation bubbles behind moving tracers.

Interaction between substrate and tracer affects local phase structures.

Shear flow can distort and disconnect colloid-poor bridges.

Abstract

Using dynamical density functional theory and Brownian dynamics simulations we investigate the influence of a driven tracer particle on the density distribution of a colloidal suspension at a thermodynamic statepoint close to the liquid side of the binodal. In bulk systems we find that a localized region of the colloid-poor phase, a 'cavitation bubble', forms behind the moving tracer. The extent of the cavitation bubble is investigated as a function of both the size and velocity of the tracer. The addition of a confining boundary enables us to investigate the interaction between the local phase instability at the substrate and that at the particle surface. When both the substrate and tracer interact repulsively with the colloids we observe the formation of a colloid-poor bridge between the substrate and the tracer. When a shear flow is applied parallel to the substrate the bridge becomes distorted and, at sufficiently high shear-rates, disconnects from the substrate to form a cavitation bubble.