Dynamics of a self-propelled compound droplet

A recent experiment by Wang et al. ( Soft Matt. , vol. 17, 2021, pp. 2985–2993) shows that a self-propelled compound drop in surfactant-laden solution can autonomously change its motion from straight line to spiraling trajectory, enhancing capability for chemical detection, catalytic reaction and pollutant removal large fluid region. To understand the underlying physics of this peculiar motion, we develop two-dimensional minimal model study swimming dynamics droplet driven self-generated Marangoni stress. We find that, depending on Péclet number $Pe$ ) viscosity volume ratios two phases, swim variety trajectories, including lines, circles, zigzag curves chaotic trajectories. The moves circles when components have comparable volumes. Otherwise, it other types motions . Our simulation results circular at small are qualitatively experiment. transition between trajectories is mainly determined orientation high-order modes with respect drop's direction. For most drops, speed decays as $Pe^{-1/3}$ high numbers does single-phase drop. equal undergoes run-and-reorient due competition even odd modes.