Fabrication of micro-patterned ZrO2/TiO2 composite surfaces with tunable super-wettability via a photosensitive sol-gel technique

A patterned ZrO2/TiO2 composite surface consisted of ZrO2 bulges and TiO2 dimples was prepared utilizing a photosensitive sol-gel technique, which has a peak-valley hierarchical structure and presents excellent non-light activated superhydrophilicity. After modification by low-surface-energy molecules of 1H,1H,2H,2H-perfluorooctyltrichlorosilane (FOTS), the wettability was consequentially changed into sliding superhydrophobicity with a water contact angle (WCA) of 158 degrees and a sliding angle of 8 degrees. Ultraviolet irradiation was finally performed to degrade the FOTS layer on TiO2 dimples of the FOTS-modified ZrO2/TiO2 surface, and the obtained pinning effect could make the surface exhibit unique sticky superhydrophobicity with WCA of 154 degrees and strong adhesion to water. It was also revealed that the formation mechanism of sticky superhydrophobicity is quite different from the reported petal model and metastable model, and it can be explained by a novel intermediate model between Wenzel and Cassie models. More interestingly, the sticky superhydrophobic surface was used as a "mechanical hand" to capture water droplets from the sliding superhydrophobic surface and transfer to the superhydrophilic surface, suggesting that it has a huge potential in water droplet transportation.