A density-independent glass transition in designer active granular matter

Dense assemblies of active particles are thought to undergo dynamical arrest akin to supercooled equilibrium liquids. However, how activity modifies the approach to a glassy state continues to be debated. Addressing this question is essential even as a growing body of evidence suggests that dense assemblies of biological cells share hallmark traits of equilibrium glass physics. By designing synthetic active matter systems that capture certain key features of living ones, we systematically investigate active glassy dynamics in this model system. This allowed us to explore the interplay of nature and the degree of activity, shape and topological defects on glassy slowing down. We observed non-trivial relaxation mechanisms unique to active glasses. We anticipate that our experimental strategy will help prune theoretical predictions of active glasses.