Interfacial Dynamics in the Spontaneous Motion of an Aqueous Droplet.

Self-propelled droplets can spontaneously move using chemical energy. In several reports of self-propelled droplets, interfacial chemical reactions occur at the oil/aqueous interface to induce the Marangoni flow. While the dynamics of interfacial tension is essential to the droplet motion, there are few reports that quantitatively discuss the moving mechanism based on interfacial tension measurements. In this study, we focused on the self-propelled motion of an aqueous droplet in the oil phase, where the surfactant monoolein reacts with bromine at the interface, and estimated the physicochemical parameters related to the droplet motion based on the time series of interfacial tension. These results may reveal the general mechanism for the self-propelled motion of aqueous/oil droplets driven by the interfacial chemical reaction.