Fig. 1.

Schematic drawing of a droplet swimmer moving in surfactant solution. Due to the micellar solubilization of the oil phase, filled micelles disperse from the droplet into the solution, as shown by the yellowish shadow. Close to the droplet the free surfactant molecules are depleted, as shown by the white circle. When the droplet moves, it encounters more empty micelles in the front and leaves more filled micelles behind. The inhomogeneous interfacial surfactant coverage on the droplet then starts the Marangoni flow and sustains the motion. Drawing is not to scale.