Self-propulsion of nematic drops: novel phase separation dynamics in impurity-doped nematogens

We report a novel phase separation dynamics, mediated by self-propelled motion of the nucleated drops, in a mixture of a nematogen and an isotropic dopant. We show that surface flow, induced by the gradient in the concentration of the dopant expelled by the growing drops, provides the driving force for the propulsion of nematic droplets. While the liquid crystal-isotropic transition is used here to demonstrate the phenomenon, self-propulsion should be observable in many other systems in which the dynamics of a conserved order parameter is coupled to a nonconserved order parameter.