Effects of surface texture on wetting

Wetting is a phenomena which occurs when a droplet tends to spread out on a surface. The extreme behaviour of wetting, also known as superhydrophilicity, is found to be useful in many real life applications and has been receiving considerable attention. In general, wetting effect of a surface can be improved by treating it with special chemicals or altering its roughness; both of which aim to change the interfacial interactions among the phases of matter involved in the system. An extensive research has been conducted to seek ways to generate a superhydrophilic surface by fabricating micropillars, sometimes with nanostructures, artificially on a surface to simulate the roughness structures. One of the advantages of using this method is that it allows a study of the wetting effects in a more controlled manner through the use of most of the theoretical approaches available in this field. However, this usually incurs high costs and requires a long fabrication process. The limitations mentioned above have motivated the method used in this project – altering the surface roughness using sandpapers. It is a cheap and effective way to generate reasonably good wetting effects on a surface. In addition to roughness alteration, simple textures were also created on the surface while it is being sanded. Past research has suggested a high aspect ratio of roughness structures in creating a superhydrophilic surface. Therefore, the grit sizes of sandpapers ranging from 24 to 80 were used in this project. The types of surface texture were also varied to investigate their effects on wetting. The experimental results showed that sanding a stainless steel and an aluminium surface with unidirectional texture, using a coarse grit sandpaper reduced the contact angles of droplets to nearly half of the Young’s contact angle.Bachelor of Engineering (Aerospace Engineering