Hierarchical structures for superhydrophobic and superoleophobic surfaces.

Many surfaces possessing robust super liquid repellency, are hierarchically structured on the nano- and micrometer scale. Several examples are found in nature such as the self-cleaning leaves of lotus plants and anisotropic, water guiding rice leaves. Each surface design has unique properties optimized for specific wetting conditions. In this article, we review both natural and artificial hierarchical surface structures and their function in repelling liquids. We discuss different types of structures needed in various wetting situations and draw some general conclusions as a guideline for designing robust superhydrophobic and superoleophobic surfaces.