Complete wetting characteristics of micro/nano dual-scale surface by plasma etching to give nanohoneycomb structure

A variety of flat superhydrophilic surfaces have been fabricated for biological and industrial applications. We report here the preparation of a simple and inexpensive non-polar curved superhydrophilic surface. This surface has dual-scale surface roughness, on both micro- and nanoscales. Curved surfaces with a near-zero water contact angle and ‘complete wetting’ are demonstrated. By using a conventional plasma etching process, which creates microscale irregularity on an aluminum surface, followed by an anodization process which further modifies the plasma etched surface by creating nanoscale structures, we generate a surface having irregularities on two-scales. This surface displays a semi-permanent superhydrophilic property (if the surface has no damage by the exterior failure), having a near-zero contact angle with water drops. We further report a simple and inexpensive curved (i.e., non-planar) superhydrophilic structure with a near-zero contact angle. The dual-scale character of the surface increases the capillary force effect and reduces the energy barriers of the nanostructures.