Multifunctional surfaces with reversible characteristics have gained great attention due to their various envisioned applications. We report on the development of surfaces exhibiting both photocatalytic activity and reversible wettability. Initially, irradiation of silicon wafers with femtosecond laser pulses produces a surface with dual-scale roughness in the micro-and nanoscale. Subsequently, the hierarchically roughened silicon surfaces are coated with ZnO following a simple sol− gel process. The manufactured artificial surfaces exhibit reversible wettability from superhydrophilic (upon UV irradiation) to superhydrophobic (upon heating), while the specimens reveal high photocatalytic activity as illustrated by the decolorization of methylene blue utilized as a model dye. The surfaces exhibit reproducibility and stability over a number of cycles.

Multifunctional surfaces with reversible wetting characteristics are fabricated utilizing end-anchored polymer chains on hierarchically roughened surfaces. Temperature- and/or pH-responsive surfaces are developed that exhibit reversible and controllable wettability, from the "parahydrophobic" behavior of natural plant leaves all the way to superhydrophilic properties in response to the external stimuli. For this purpose, dual scale micro/nanoroughened surfaces were prepared by laser irradiation of inorganic surfaces (Si wafers) utilizing ultrafast (femtosecond) laser pulses under a reactive gas atmosphere. End-functionalized polymer chains were anchored onto those surfaces utilizing the "grafting to" method; poly(N-isopropylacrylamide), PNIPAM, and poly(2-vinylpyridine), P2VP, were used for the formation of monofunctional as well as mixed brushes. The surfaces exhibit "parahydrophobic" behavior in the hydrophobic state (high temperature and/or high pH), with high static contact angles (∼120°) and high water adhesion (∼30° contact angle hysteresis), whereas they show superhydrophilic behavior in the hydrophilic state (low temperature and/or low pH). The surfaces were tested for their wettability under repetitive cycles and found to be stable and reproducible.

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