Generic model for tunable colloidal aggregation in multidirectional fields

TL;DR

This study uses Brownian Dynamics simulations to explore how colloidal particle aggregation can be tuned from point-dipole to patchy interactions, revealing transitions in aggregation behavior and lattice structures.

Contribution

It introduces a continuous model for colloidal interactions that bridges point-dipole and patchy particles, demonstrating how aggregation mechanisms and structures change accordingly.

Findings

Transition from DLCA to slippery DLCA with rotating bonds

Change in aggregate lattice from square to hexagonal

Temperature induces a phase transition to fluid state

Abstract

Based on Brownian Dynamics computer simulations in two dimensions we investigate aggregation scenarios of colloidal particles with directional interactions induced by multiple external fields. To this end we propose a model which allows continuous change in the particle interactions from point-dipole-like to patchy-like (with four patches). We show that, as a result of this change, the non-equilibrium aggregation occurring at low densities and temperatures transforms from conventional diffusion-limited cluster aggregation (DLCA) to slippery DLCA involving rotating bonds; this is accompanied by a pronounced change of the underlying lattice structure of the aggregates from square-like to hexagonal ordering. Increasing the temperature we find a transformation to a fluid phase, consistent with results of a simple mean-field density functional theory.