Water droplet dynamics on a heated nanowire surface

Abstract

When a liquid droplet is deposited onto a heated surface, evaporation occurs. If the temperature of the surface is sufficiently high, bubbles are released from activated nucleation sites, making the heat transfer more efficient. However, if the temperature of the surface is further increased above the Leidenfrost point, a vapour cushion will form underneath the droplet, deteriorating the heat transfer between the surface and the droplet. In this work, we show that patterned Si nanowires can allow shifting the Leidenfrost temperature while maintaining a minimum droplet evaporation lifetime. In particular, it is observed that the Leidenfrost point is reached when the phase-change time scale compared to the wicking time scale becomes dominant. In this situation, the energy of the lift-off process is not sufficient for allowing the droplet to reach a sufficient height from where the droplet can penetrate in the porous surface.