Rewritable superhydrophilic-superhydrophobic patterns on a sintered titanium dioxide substrate

This Letter describes a new fabrication process for superhydrophilic- superhydrophobic patterns on a TiO ₂ surface using a combination of an inkjet technique and the site-selective decomposition of a self-assembled monolayer (SAM) by a photocatalytic reaction under UV irradiation. To induce high surface wettability, we carried out simple calcination of a Ti substrate. The substrate was thus oxidized to titanium oxide and had a vortex-like rough morphology, which was suitable for the formation of wettability patterns. Furthermore, the substrate can be regenerated after elimination of the superhydrophilic-superhydrophobic patterns by the photocatalytic decomposition of TiO ₂ using UV irradiation, and the patterns are deposited again. The renewed surface that we created had a wettability pattern that was different from the preceding pattern. This process is based on a TiO ₂ surface and should offer a renewable, resource-saving, and environmentally friendly methodology for the formation of wettability patterns.