Tuning Hydrophobicity with Honeycomb Surface Structure and Hydrophilicity with CF4 Plasma Etching for Aerosol-Deposited Titania Films

Abstract

A tunable surface that promotes either hydrophobic or hydrophilic behavior of TiO2 films is produced with aerosol deposition. This process is capable of mass production by high-speed coating at room temperature without any wet chemicals, and therefore the process has the potential to be economically viable, energy efficient, and environmentally friendly. Functional TiO2 films between 1 and 18 mu m thick are produced by directly depositing dry, 1-mu m TiO2 powders accelerated through a supersonic nozzle. Tunable film morphology due to a rough honeycomb surface structure yields variable water contact angles. When plasma treated with CF4, the films exhibit superhydrophilicity despite the rough honeycomb surface structure. Superhydrophilicity is due to the incorporation of fluorine in the film as shown using XPS.