Photo-induced in situ switching of surface wettability of Titania films under air and oil environment

We present a facile method for fabrication of Titania (TiO₂) based superhydrophobic surfaces by silanization with wettability switching from superhydrophobic to superhydrophilic under ultraviolet (UV) light irradiation. The dynamic of surface wettability under UV irradiation was tested under ambient environment as well as in oily environment. We synthesized TiO₂ based superhydrophobic surface with contact angle as high as 154° for advancing angle and 152° for receding angle in air. A dramatic decrease of the contact angle to 0° was observed when the TiO₂ sample was irradiated with UV light. No appreciable change in contact angle was observed when sample was tested under oily medium. However, a switching from Cassie state to Wenzel state was occurred, resulting in a sticky superhydrophobic surface. Photocatalyic activity induced in organic degradation was probably the major cause of the wettability switching.