When a volatile droplet is deposited on a heated conducting substrate below the boiling temperature of the liquid, it contracts rather than spreading and moves spontaneously. Increasing substrate temperature changes the propulsion mode of the droplet from slow, uniform to fast and chaotic movements. We propose that spontaneous droplet motion results from unsteady thermo-capillary convection. Due to a larger thermal gradient along the droplet interface, the droplet is exposed to stronger contracting Marangoni flow, and spontaneous symmetric breaking of Marangoni flow induces droplet motion.
This work is licensed under the Creative Commons Attribution-NonCommercial 4.0 International License. Any reuse must credit the author(s) and provide a link back to this page.