Activity-controlled Annealing of Colloidal Monolayers

TL;DR

This study demonstrates that adding self-propelled colloids to passive bead monolayers significantly accelerates annealing, revealing how internal activity can control material properties beyond equilibrium.

Contribution

It introduces a novel method of using active colloids to control and accelerate the annealing process in colloidal monolayers, supported by experiments and simulations.

Findings

Active colloids accelerate annealing of passive beads.

Active dopants either travel uniformly or co-localize at grain boundaries.

A dynamical transition in annealing mechanism was observed.

Abstract

Molecular motors are essential to the living, they generate additional fluctuations that boost transport and assist assembly. Self-propelled colloids, that consume energy to move, hold similar potential for the man-made assembly of microparticles. Yet, experiments showing their use as a powerhouse in materials science lack. Our work explores the design of man-made materials controlled by fluctuations, arising from the internal forces generated by active colloids. Here we show a massive acceleration of the annealing of a monolayer of passive beads by moderate addition of self-propelled microparticles. We rationalize our observations with a model of collisions that drive active fluctuations to overcome kinetic barriers and activate the annealing. The experiment is quantitatively compared with Brownian dynamic simulations that further unveil a dynamical transition in the mechanism of annealing. Active dopants travel uniformly in the system or co-localize at the grain boundaries as a result of the persistence of their motion. Our findings uncover the potential of man-made materials controlled by internal activity and lay the groundwork for the rise of materials science beyond equilibrium.