Rapid erasing of wettability patterns based on TiO2-PDMS composite films

TiO2-polydimethylsiloxane (TiO2-PDMS) composite films are prepared using the sol–gel method from a Ti(OBu)4–benzoylacetone solution containing PDMS. The prepared films are cured by irradiation with ultraviolet (UV) light. Structural changes in the films after UV irradiation are confirmed by UV–vis absorption experiments, which show that an absorption band characteristic of the benzoylacetonate chelate rings disappears. This finding is ascribed to structural changes associated with the dissociation of the chelate rings. The IR spectra of the thin films exhibit a broad absorption band after UV irradiation, indicating that a Ti–O–Ti network forms in the thin film. Contact angles are measured for the TiO2-PDMS thin films, showing wettability conversion from hydrophobic to superhydrophilic states by irradiation with oxygen plasma for 1 s. This phenomenon is explained by XPS experiments which reveal that the number of carbon atoms decreases, whereas the number of oxygen atoms increases on the surface of the TiO2-PDMS composite films. Finally, hydrophobic–superhydrophilic patterns are fabricated based on a patterned TiO2-PDMS composite film. The film displays a rapid change to superhydrophilicity over the whole film surface upon plasma irradiation for 1 s, which means that the wettability patterns are rapidly erasable.