Tuning hydrophobicity of TiO₂ layers with silanization and self-assembled nanopatterning

The wettability of TiO₂ layers is controlled by forming highly ordered arrays of nanocones using nanopatterning, based on self-assembly and dry etching. Nanopatterning of TiO₂ layers is achieved via formation of self-assembled monolayers of SiO₂ spheres fabricated using the Langmuir-Blodgett technique, followed by dry etching. Three types of TiO ₂ layers were fabricated using the sol-gel technique, sputtering, and thermal process in order to address the relationship between the wettability and the structure of TiO₂ nanostructures. Compared to a thin film TiO₂ layer, the nanopatterned TiO₂ samples show a smaller static water contact angle (i.e., where the water contact angle decreases as the etching time increases), which is attributed to the Wenzel equation. When TiO₂ layers are coated by 1H,1H,2H,2H-perfluorooctyltrichlorosilane, we observed the opposite behavior, exhibiting superhydrophobicity (up to contact angle of 155) on the nanopatterned TiO₂ layers. Self-assembled nanopatterning of the TiO₂ layer may provide an advanced method for producing multifunctional transparent layers with self-cleaning properties.