Dynamics of droplet impact and evaporation on the regular micro-grooved and irregular microstructured surfaces

Abstract

The dynamics of droplet impact and evaporation on the regular micro-grooved and irregular microstructured surfaces are experimentally investigated in this study. The regular micro-grooved and irregular micro structured surfaces are fabricated by a method combining ultraviolet lithography and Ni micro-electroforming process, and electrochemical etching, respectively. It is found that the surface temperature has little effect on the curves of spreading factor in the first spreading phase, as the first spreading phase is governed by the impact of the kinetic energy. At low surface temperature, the total evaporation time for three surfaces is almost same. When the surface temperature exceeds 100 °C, the total evaporation time for the three surfaces shows the differences, and in this regime the droplet mass can mainly be accelerated by the formation of bubbles. At the surface temperature of 104 °C, the micro-cavities of irregular microstructured surface provide more active nucleation sites than that of flat and regular micro-grooved surfaces, which contributes to shorten the total evaporation time. At the surface temperature of 165 °C, the large amount of secondary droplets eject outward on the flat surface, which has not been seen on the regular micro-grooved and irregular microstructured surfaces.