Surfing the hot spot

The characteristic features of Leidenfrost drops, which are very mobile, do not boil, and if confined in a hot ring, last very long, despite the very high temperature of the substrates are discussed. If these drops sit on a cushion of its own vapor, they prevent contact with the solid. The amplitudes of the motion is limited to the size of the drop or the lateral extent of the gradient on the surface. Drops are found to move spontaneously on substrates, whatever the nature of the liquid, provided they are in a Leidenfrost situation. The drops move quite fast perpendicularly to the steps, climbing the steps and sliding down the slope. The heat-induced evaporation of the Leidenfrost drops provides both the energy for their motion and the air cushioning that increases their mobility.