Active fluidization in dense glassy systems

TL;DR

This study uses molecular dynamics simulations to show that activity in dense glassy systems can induce fluidization, cage breaking, and a transition from fragile to strong glass behavior, relevant to active colloids and cellular dynamics.

Contribution

It demonstrates how self-propulsion can fluidize dense glasses and induce a fragile-to-strong transition, a novel insight into active glassy matter.

Findings

Activity induces cage breaking and fluidization.

Diffusion coefficient becomes less temperature-dependent with activity.

Active particles tend to cluster and exhibit a fragile-to-strong glass transition.

Abstract

Dense soft glasses show strong collective caging behavior at sufficiently low temperatures. Using molecular dynamics simulations of a model glass former, we show that the incorporation of activity or self-propulsion, f0, can induce cage breaking and fluidization, resulting in a disappearance of the glassy phase beyond a critical f0 . The diffusion coefficient crosses over from being strongly to weakly temperature dependent as f0 is increased. In addition, we demonstrate that activity induces a crossover from a fragile to a strong glass and a tendency for clustering of active particles. Our results are of direct relevance to the collective dynamics of dense active colloidal glasses and to recent experiments on tagged particle diffusion in living cells.