Active Glasses Mimic Cyclically Sheared Amorphous Solids

Active glasses are dense and disordered assemblies of self-propelled particles, making them relevant to many biological contexts. Using large-scale simulations, we investigate activity-induced annealing and its mechanical consequences. We find a close correspondence between fluidization under internal (active) driving and the yielding transition of amorphous solids under cyclic shear. The active system reproduces all the major hallmarks of cyclic shear: a similar yielding diagram with comparable sensitivity to initial energy, diverging timescales to reach steady states, and the crucial role of stress reversals in the annealing process. Additionally, we show that both systems can encode memories of their respective driving amplitudes, which can be retrieved using very similar readout protocols. Finally, by probing the mechanical response in activity-annealed states, we demonstrate that, given the appropriate sample geometry, a transition in failure mode from ductile (smooth stress response) to brittle (abrupt stress drop) is possible. Such tuning of failure modes by active constituents could have implications ranging from the design of smart materials to the understanding of age-related changes observed in tissues.