Effect of Fine Structures Formed by Nanoimprinting Using Anodic Porous Alumina Mold on Surface Hydrophobicity

Abstract

A surface with a simple nanopillar array and hierarchical micro-/nano structures consisting of microconvexes and a surface with a nanopillar array were fabricated by nanoimprinting using two types of anodic porous alumina mold. On both surfaces, the height of polymer nanopillars could be controlled by adjusting the anodization time for the preparation of the anodic porous alumina mold. Regarding water-repellent properties, a higher contact angle was observed on the surface with a hierarchical structure than on the surface with a simple nanopillar array. In the measurement of the water droplet sliding angle, the surface with a hierarchical structure showed higher performance characteristics than the surface with a simple nanopillar array. This is because the surface with a hierarchical structure can more easily trap air between the substrate surface and the water droplet than the surface with a simple nanopillar array. The hierarchical micro-/nano structures could be prepared repeatedly by nanoimprinting using a single mold. The method developed here for preparing a superhydrophobic surface is used for various applications, such as those requiring superhydrophobic surfaces with sliding angles.