Superhydrophobic alumina surface with high adhesive force and long-term stability

This work presents a novel alumina surface with both superhydrophobicity and strong adhesion to water. The superhydrophobic alumina surface takes on the roughened and porous morphology with the hierarchical micro- and nano-structure. The water droplet cannot enter into the larger scale of grooves while it can impregnate and wet the nipple-shaped protrusions along with the solid plateaus among protrusions. As a result, the alumina surface shows super water-repellence, and meanwhile, water droplet does not slide or roll off even while the surface is tilted vertically and turned upside down. The system accords with the transitional state between Wenzelʹs model and Cassie-Baxterʹs model. Moreover, the alumina surface remains the strong water-repellence and adhesive property in a wide pH range from 1 to 11 after being in the atmosphere for a year, indicating that the superhydrophobic alumina surface has excellent durability and stability.