Photoinduced switchable underwater superoleophobicity-superoleophilicity on laser modified titanium surfaces

Switchable underwater superoleophobicity-superoleophilicity on femtosecond laser-induced rough TiO₂ surfaces by alternate UV irradiation and dark storage is achieved for the first time. Femtosecond laser ablation not only forms a micro/nanoscale hierarchical rough structure but also oxidizes the Ti materials, resulting in a rough TiO₂ layer covering on the surface. The reversible switching of underwater oil wettability is caused by photoinduced switching between superhydrophobic and superhydrophilic states in air. These rough TiO₂ surfaces can even respond to visible light. We believe this subtle switching method will be potentially applied in the biological and medical fields.