Active Surface Flows Accelerate the Coarsening of Lipid Membrane Domains

Phase separation of multicomponent lipid membranes is characterized by the nucleation and coarsening of circular membrane domains that grow slowly in time as $\ensuremath{\sim}{t}^{1/3}$, following classical theories of coalescence and Ostwald ripening. In this Letter, we study the coarsening kinetics of phase-separating lipid membranes subjected to nonequilibrium forces and flows transmitted by motor-driven gliding actin filaments. We experimentally observe that the activity-induced surface flows trigger rapid coarsening of noncircular membrane domains that grow as $\ensuremath{\sim}{t}^{2/3}$, a $2\mathsf{x}$ acceleration in the growth exponent compared to passive coalescence and Ostwald ripening. We analyze these results by developing analytical theories based on the Smoluchowski coagulation model and the phase field model to predict the domain growth in the presence of active flows. Our Letter demonstrates that active matter forces may be used to control the growth and morphology of membrane domains driven out of equilibrium.