Fabrication of Micro-/Submicro-/Nanostructured Polypropylene/Graphene Superhydrophobic Surfaces with Extreme Dynamic Pressure Resistance Assisted by Single Hierarchically Porous Anodic Aluminum Oxide Template

By applying a three-step anodic oxidation method followed by etching and pore widening treatment, etched micro-/submicroscale pits of similar to 2 mu m and similar to 230 nm as well as anodized nanopores of similar to 70 nm are combined to form hierarchically porous anodic aluminum oxide (HP-AAO) templates. Hierarchical micro-/submicro-/nanostructured polypropylene/graphene (HMSNS-PP/GP) superhydrophobic surfaces are laminated by a single HP-AAO template, exhibiting the similar arrangement, size, and shape with hierarchical papillae on lotus leaf surfaces. As expected, such a lotus-inspired HMSNS-PP/GP surface has an extremely small roll-off angle of similar to 0.5 degrees and a large contact angle of 155.0 degrees, exhibiting high-efficiency self-cleaning characteristics. The HMSNS-PP/GP surface is endowed with static and dynamic wetting stabilities, which are reflected in immersion and impacting tests. After immersion, the HMSNS-PP/GP replica remains fully spotless accompanied with the ability to work under a hydrostatic pressure of similar to 3626 Pa for at least 60 min. After impact, the maximum height of bounced droplets is up to 12.4 mm (i.e., 5.3 times the diameter of the droplet) at a Weber number of similar to 32.12.