Self-assembly of diverse alumina architectures and their morphology-dependent wettability

This work reports the fabrication of diverse nanostructured alumina films under high-field anodization in oxalic-acid electrolytes. Different surface morphologies of these alumina films can be obtained by adjusting reaction parameters, which was ascribed to the anisotropic chemical etching induced by the reaction heat and the concentration gradient of the oxalic-acid solution along the nanopore channels during the high-field anodization process. These alumina surfaces without coating low energy materials show remarkable morphology-dependent wettability. Specially, the alumina surface consisting of porous underlayer and nanowire pyramids with no chemical modification reveals excellent super water-repellent behavior for the first time. This study could provide a new approach for designing functional surfaces with tunable wettability.