Droplet migration during condensation on chemically patterned micropillars

Abstract

We demonstrate the migration of small water droplets from the side wall of a micropillar onto its top surface during dropwise condensation without application of an external force. The observed droplet migration occurs due to the difference in wettability between the hydrophobic sides and hydrophilic top surfaces of the micropillars imposed by a novel fabrication process. The movement of condensate from the pillars' side walls onto their tops is suggested as a method for shifting condensate from a Wenzel to a Cassie-Baxter state to promote droplet detachment. In this communication, we also emphasize the use of combined surface texturing and wettability patterning to prompt the migration of condensate on pillars for the effective design of surfaces for high condensation heat transfer performance.