Dynamics and rheology of active glasses

TL;DR

This paper develops a mode-coupling theory-based model to study active colloidal glasses, revealing that activity shifts the glass transition to higher densities and softens the material's mechanical response, aligning with recent simulations.

Contribution

It introduces a simple theoretical model for active glasses that predicts activity effects on the glass transition and mechanical properties, extending understanding beyond passive systems.

Findings

Active particles increase the glass transition volume fraction.

Active glasses exhibit reduced yield stress and nonergodicity parameter.

The model's predictions align with recent Brownian dynamics simulations.

Abstract

Within the framework of mode-coupling theory, we present a simple model for describing dense assemblies of active (self-propelled) spherical colloidal particles. For isotropic suspensions, we demonstrate that the glass transition is shifted to higher volume fraction by the addition of activity, in agreement with recent Brownian dynamics simulations. Activity-induced changes in the static structure factor of the fluid are predicted. The mechanical response of an active glass to applied strain is shown to be softer than the corresponding passive glass; both the nonergodicity parameter and the yield stress reduce with increasing activity.