Precursor Film Mediated Spontaneous Migration of Condensed Microdroplets

Abstract

In this paper, we investigated the microdroplet condensation of a low surface tension liquid on flat surfaces by using reflection interference confocal microscopy. It was found that the microdroplets nucleated on the hydrophilic quartz surface, which showed very low contact angles of ~5°, spontaneously migrate toward relatively larger droplets, while those on the hydrophobic polydimethylsiloxane surface did not move. We attribute this migration to the combined effect of thermocapillary motion induced by latent heat and the reduction of a resistive force to migration by the ultrathin precursor film formed only on the hydrophilic surface.