Dynamic swarms regulate the growth and morphology of membrane domains

Our experiments investigate the dynamics of cell membranes attached to the underlying cytoskeleton and molecular motors. We developed a synthetic model of a multiphase lipid bilayer coupled to purified actin and myosin proteins. In the presence of gliding actin filaments, membrane domains evolve into unique structures, a distinct deviation from circular shapes observed in coarsening. These structures frequently merge and break up, leading to arrested domain growth. In this work, we combine the Toner-Tu equation for flocking dynamics with a phase field model to study such systems of activity-mediated phase separation. Our model predicts the growth and structure of domains in the presence of swarming flows. We find that the domain structure reaches a dynamic steady state. We extend our analysis to different swarms and show that this steady-state morphology is correlated with the peak of the velocity spectra. We further analyze the domain structure by deriving an evolution equation of interfacial fluctuations and show that the nature of active stresses controls the growth of initial perturbations at the interface.