Wettability of Liquid Mixtures on Porous Silica and Black Soot Layers

Sophisticated manipulation of surface roughness and solid surface energy are widely used to design super-hydrophobic layers. In this work, we designed highly porous silica layer with contact angle (CA) of 145°, and its robustness was promoted with thermal treatment. Wettability of coated layer is studied with CA measurement for different liquid surface tensions using diluted organic solvents (ethanol, acetone or ethylene glycol) with distilled water. Zisman plot is also used to estimate the surface energy of the porous silica. The results are compared with coated black soot as a hydrophobic layer. Moreover, thin layer of Au (~10 nm) was coated on the porous silica layers to study the effects of chemical properties on the wetting behavior. The thickness of the Au thin layer is negligible compared to the surface roughness, so the drastic decrease in CA rates can be related to the layers' porosity and the affinity of solvents to liquid/air and liquid/solid interfaces.