Hydrodynamic interactions of droplets ladened by active agents

Active droplets which can autonomously locomote are of both fundamental interest and practical importance. Here we consider droplets ladened by active agents and investigate the hydrodynamic interactions between these droplets. Specifically, we use multi-blob simulation to investigate the dynamics of droplets above a no-slip bottom wall, which are driven by neutral swimmers on their interfaces. For single droplets, we observe dynamical trajectories that exhibit petal-like circular motions. In systems with multiple droplets, each subjected to a restoring force and immersed in an unbounded domain, we identify several dynamic modes, including spontaneous reorientation, phase-locking, and synchronization. These phenomena result from translation-rotation hydrodynamic coupling. Furthermore, we propose to use spatial perturbation to control the synchronization dynamics of these active droplets. Taken together, our work sheds light on the active surface flow mediated autonomous motions of active droplets.