Tuning hydrophobicity with honeycomb surface structure and hydrophilicity with CF ₄ plasma etching for aerosol-deposited titania films

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 TiO ₂ films between 1 and 18 μm thick are produced by directly depositing dry, 1-μm 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.