Phototunable underwater oil adhesion of micro/nanoscale hierarchical-structured ZnO mesh films with switchable contact mode

Controllable surface adhesion of solid substrates has aroused great interest both in air and underwater in solving many challenging interfacial science problems such as robust antifouling, oil-repellent, and highly efficient oil/water separation materials. Recently, responsive surface adhesion, especially switchable adhesion, under external stimulus in air has been paid more and more attention in fundamental research and industrial applications. However, phototunable underwater oil adhesion is still a challenge. Here, an approach to realize phototunable underwater oil adhesion on aligned ZnO nanorod array-coated films is reported, via a special switchable contact mode between an unstable liquid/gas/solid tri-phase contact mode and stable liquid/liquid/solid tri-phase contact mode. The photo-induced wettability transition to water and air exists (or does not) in the micro/nanoscale hierarchical structure of the mesh films, playing important role in controlling the underwater oil adhesion behavior. This work is promising in the design of novel interfacial materials and functional devices for practical applications such as photo-induced underwater oil manipulation and release, with loss-free oil droplet transportation.