A strategy of fast reversible wettability changes of WO3 surfaces between superhydrophilicity and superhydrophobicity

As-prepared WO(3) nanostructure films on alumina or tungsten substrates by a facile hydrothermal method exhibit a superhydrophilic property. An effective strategy is proposed to control the wettability of WO(3) films in a reversible manner between superhydrophilicity and superhydrophobicity with a rapid response. By controlling the process of adsorption/desorption of n-dodecanethiol associated with the light-induced plating Ag nano-grains on WO(3) nanostructures, it only takes about 25 min to fulfill the wettability change from superhydrophilicity to superhydrophobicity, and only 30 s to finish the reversed change. Moreover, the contact angles of WO(3) surface can be tuned by controlling the etching time of superhydrophobic WO(3) surfaces in a solution of nitric acid containing 5 mM sodium dodecyl benzene sulfonate. Electrowetting process is successfully demonstrated to trap a water drop onto the superhydrophobic WO(3) surfaces. Considering WO(3) is one of typical electrochromic materials, researches on the effect of coupling between electrowetting and electrochromic properties would be more promising.