Ultrafast transients dictate droplet self-propulsion on heated surfaces

Self-propulsion of condensed matter has conventionally been controlled by surface geometries, interfacial energies, temperature, and electro-magnetic fields without considering the importance of the substrate’s thermal properties. Here, we vary the thermal effusivity of the substrate over one order of magnitude to control rapid droplet propulsion (~1-10cm/s) on lubricated surfaces. Using insights from high-speed infrared thermography, we establish a transient, analytical model that predicts whether a droplet will boil, propel, or Leidenfrost at steady state based on the substrate material and initial temperature. We demonstrate, that the model allows for the precise control of phase change phenomena beyond propulsion on various materials and surfaces across a large range of temperatures up to 200°C.