Superhydrophobicity of direct plasma synthesized and deposited thin films: Effect of chemical-induced and substrate roughness

Surface superhydrophobicity results from combinations of surface free energy and roughness. In this contribution, plasma-induced polymerizations are studied for the direct deposition of coatings with different surface chemistries and topographies. The formation of wrinkles in combination with textured substrates (sandpapers) leads to a transition in the water contact angle (WCA), transforming the substrate from hydrophobic to superhydrophobic (WCA > 150°). Initial correlations of pitch (P), diameter (d), and height (h) of the surface elements in the sandpaper, the chemical-induced roughness and the decrease of wettability are carried out to assist on the design of a plasma etching pre-treatment for substrate texturing. By coating plasma etched silicon wafers, superhydrophobic surfaces are produced with WCA values around 168° and hysteresis (HA) and tilting angles as low as 5°.