Shivakote Village

Pattern formation in active biological matter typically arises from the feedback between chemical concentration fields and mechanical stresses. The actomyosin cortex of cells is an archetypal example of an active thin film that displays such patterns. Here, we show how pulsatory patterns emerge in a minimal model of the actomyosin cortex with a single stress-regulating chemical species that exchanges material with the cytoplasm via a linear turnover reaction.

Our experiments on a sphere falling from rest under gravity in Stokes flow show the development of unsteady flow structures and significant history effects. Unlike in steady Stokes flow, we observe a vortex ring forming around the sphere and drifting away, which is captured by our unsteady Stokes theory.