Sessile droplet wetting & evaporating on patterned surfaces

Abstract

The wetting and evaporation behaviour of sessile droplets on micro patterned surfaces have been studied extensively due to their potential applications in various fields. In this study, we investigated the wetting and evaporation processes of cetyltrimethylammonium bromide (CTAB) sessile droplets on a micro pyramid substrate using optical microscopy. Three different concentrations of CTAB, 0.4mM, 0.7mM, and 1.0mM and 1.0mM with Polystyrene Particles were examined to understand the effects of surfactant concentration on the droplet behaviour. The droplet contact angles were measured on both horizontal (line of sight: 0°) and inclined planes (line of sight: 45°) of the micro pyramid substrate. The results showed that the contact angles on the inclined plane were lower than those on the horizontal plane, and all three concentrations of CTAB exhibited hydrophilic behaviour on the inclined plane. The drying patterns of the droplets also showed interesting features, such as the coffee ring effect and crystallization of CTAB. This study provides valuable insights into the wetting and drying behaviour of sessile droplets on patterned substrates and can lead to further investigations on the design and development of microfluidic devices and other related applications.