Pattern formation in colloidal explosions

TL;DR

This paper investigates the non-equilibrium pattern formation in colloidal systems during explosions caused by magnetic repulsion, combining experiments, theory, and simulations to understand the resulting structures and dynamics.

Contribution

It introduces a comprehensive analysis of colloidal explosion patterns, linking experimental observations with theoretical and simulation models to characterize non-equilibrium behaviors.

Findings

Formation of concentric rings during multi-colloid explosions

Persistence of zigzag patterns even with weak magnetic interactions

Quantitative description of non-harmonic optical traps through mode analysis

Abstract

We study the non-equilibrium pattern formation that emerges when magnetically repelling colloids, trapped by optical tweezers, are abruptly released, forming colloidal explosions. For multiple colloids in a single trap we observe a pattern of expanding concentric rings. For colloids individually trapped in a line, we observe explosions with a zigzag pattern that persists even when magnetic interactions are much weaker than those that break the linear symmetry in equilibrium. Theory and computer simulations quantitatively describe these phenomena both in and out of equilibrium. An analysis of the mode spectrum allows us to accurately quantify the non-harmonic nature of the optical traps. Colloidal explosions provide a new way to generate well-characterized non-equilibrium behaviour in colloidal systems.