Droplet wetting and evaporation on hydrophilic and hydrophobic surfaces

Abstract

The study is to investigate the behaviour of droplet wetting and evaporation on hydrophilic and hydrophobic surfaces. There are many related industrial applications of wetting and evaporation such as in DNA mapping and surface patterning. In particular, droplets will be from solutions of deionized water and Isopropyl alcohol and the surfaces are soda lime glass, Polytetrafluoroethylene and Indium Tin Oxide. Polytetrafluoroethylene coating will act as the hydrophobic surface while Indium Tin Oxide coating will act as the hydrophilic surfaces. The wetting of the droplet will be determined by the contact radius of the droplet and hence the size and spreading of droplet on the surface. The evaporation of the droplet will be seen from the different modes of evaporation such as constant contact angle or constant contact radius modes and the rate of evaporation. The experiments using Isopropyl alcohol and heating will change the surface tension properties of the droplet and investigate the effects of surface tension on wetting and evaporation of the droplet. On the other hand, the experiments using patterned surface Indium Tin Oxide film will investigate the effects on patterned surfaces compared to smooth surfaces. Through the studying of the droplet behaviour, potential application of droplet interaction with different surface types can be applied to microfluidic devices that explore properties of fluid at a microscale. Potential future studies may include the pinning effect onto the edge of the patterned surface by droplets and usage of other solutions and substrate with different surface tension and properties.