TiO2-based superhydrophobic–superhydrophilic pattern with an extremely high wettability contrast

Abstract

Rough nanostructured anatase TiO2 surfaces containing many pores were prepared by the hydrothermal-based method. Surface modification with self-assembled monolayers (SAMs) of octadecylphosphonic acid (ODP) resulted in the superhydrophobic surface with an extremely high static water contact angle (CA) of 173.6°±1.7°. This superhydrophobic surface could be converted into a superhydrophilic surface with a water CA of nearly 0° by irradiating it with ultraviolet (UV) light, which induced photocatalytic decomposition of the ODP SAM. A superhydrophobic–superhydrophilic pattern with an extremely high wettability contrast (a water CA difference of over 170°) could be fabricated on the ODP-modified TiO2 surface by area-selective UV irradiation through a photomask. This is the report of the TiO2-based superhydrophobic–superhydrophilic pattern with a water CA difference of over 170°, and it may be possible to use such patterns for various applications.