Turbulence-induced fluctuating interfaces in heterogeneously active suspensions

separating spatially localized turbulence from jammed frictional surroundings. We characterize the intermittent and multiscale fluctuations of this interface and also investigate how heterogeneity influences mixing via the residence times of Lagrangian tracers. This work reveals how naturally occurring heterogeneities could decisively steer active flows into more complex configurations than those typically studied. Apart from curious parallels to droplet dynamics, front propagation and turbulent mixing layers, activity heterogeneities also present a viable route to locally controlling active flows.