Orthogonal Wettability of Hierarchically Textured Metal Meshes as a Means of Separating Water/Oil Emulsions

The removal of submicrometer‐sized oil droplets from water remains a key challenge in engineering the separation of emulsions and has emerged as an urgent imperative given the increasing use of unconventional extractive processes. In this work, the authors demonstrate that a substrate with hierarchical texturation shows pronounced differences in the wettability of water and hexadecane, thereby, facilitating the separation of these two disparate liquids at room temperature and pressure. The multiscale textured substrates are assembled using a facile and readily scalable process, wherein ZnO nanotetrapods are spray‐deposited onto a steel mesh with micron‐sized features. Separation efficiencies well over 99% are accessible by simply flowing emulsions across these hierarchically textured surfaces.