Self-propulsion Suppression and Cyclic Levitation of Vaporizing Glycerol-Water Droplets

During recalescence at low pressures, sessile water droplets exhibit rapid self-propulsion driven by asymmetric vaporization flux on the freezing droplet surface. This dynamic behavior prompts reevaluation of the physics of multiphase transitions and challenges fluid control in extreme environments. Here, we demonstrate that adding a small amount of glycerol to water significantly reduces the propulsive vaporization during recalescence by lowering the freezing temperature, thereby suppressing self-propulsion. Instead, the glycerol-water droplets display gentle, intermittent levitation, cycling through distinct phases of "dwelling, liftoff, flight, and impact". Using high-speed imaging and theoretical modeling, we show that this cyclic levitation arises from self-sustaining thermal oscillations. Localized heating from a micro-structured substrate generates vapor overpressure to initiate liftoff, while vaporization cooling during flight resets the droplet for the subsequent cycle. Our findings reveal a tunable regime of vaporization-driven droplet dynamics controlled by composition, offering novel approaches for applications in advanced material processing and insights into processes such as extraterrestrial particle transport.