Effect of nano-patterning on oleophobic properties of a surface
Molecular dynamics simulations are conducted to study the effect of nano-patterning on the wettability of a surface by hexadecane (C16H34) and decane (C10H22) nano-droplets. Initially the effect of the surface lattice size on the wettability of an atomically smooth surface is studied showing it becomes more oil repelling (oleophobic) as the lattice constant is increased. Subsequently the surfaces are roughened by 2D patterns of various geometrical dimensions; the contact angle of the nano-droplet is then calculated as a function of surface roughness. The results are then compared with theoretical predictions based on Wenzel and Cassie–Baxter models. The MD simulations show that the contact angle diverges from the theoretical prediction in some cases especially when the surface is oleophilic and the size of the nano-patterns approaches the size of molecules. For most oleophobic surfaces the results from MD simulations agree with predictions from the models. Here, surfaces with superoleophobic properties are achieved with contact angles in excess of 169° by using nano-patterning.