Explosive bouncing on heated silicon surfaces under low ambient pressure.

Abstract

Droplet impingement on heated surfaces has been investigated by varying the surface textures, temperature, and droplet properties with demonstration of various phenomenological behaviors, such as evaporation, boiling, splashing, and Leidenfrost bouncing. However, the ambient pressure dependence has not been well explored, especially for ambient pressures lower than 5 kPa. By examining the ambient pressure (from 0.2 to 20 kPa) and surface temperature (from 20 to 200 °C) simultaneously, we found a novel explosive bouncing behavior which is different from Leidenfrost bouncing and only occurs at extremely low ambient pressure (≤6 kPa). Through experimental validation and mechanical analysis, we found that the explosive bouncing is caused by the dramatic explosion of the local vapor bubble and reducing the ambient pressure benefits the formation and explosion of the vapor bubble.