Dynamics and Synchronization of Surface Active Flow Driven Droplets

Active droplets which can autonomously locomote are of both fundamental interest and practical importance. Due to the action of the active agents in the droplets, hydrodynamic flows may arise on its interface, which can drive the droplets to propel. However, our current understanding of how surface active flows determine the dynamical modes of the droplets remains elusive to date. We investigate the dynamics of droplets above a no-slip bottom wall, driven by neutral swimmers on their surfaces. Specifically, we use the rigid multiblob method to simulate the dynamic trajectory of spherical droplets. Interestingly, we find that for a single droplet, its trajectories exhibit petal-like circular motions. Synchronization phenomena are observed in the presence of multiple droplets, due to translation-rotation hydrodynamic coupling. The dynamical behaviors and synchronizations are further quantitatively analyzed and explained. Our work sheds light on understanding the surface flow mediated autonomous motion of active droplets.