Bionic Mushroom Structures for Robust Super-Repellent of Low Surface Tension Liquids

Abstract Rough micro-nano structures and low surface energy chemical compositions are two essential conditions for constructing superhydrophobic surfaces. However, for low surface tension liquids, which are extremely easy to spread and wet on solid surfaces, the design of cantilever structures with internal concavity is the third important parameter to achieve their superomniphobic, whose negative geometrical inflections can effectively lock the solid-liquid-gas three phase contact line, maximize the upward component of capillary force of the suspended droplets, and provide a larger breakthrough pressure for the structured surfaces to avoid the low surface tension liquids from collapsing on the solid surfaces. Based on this, microfabrication was used to prepare mushroom structured surfaces. By precisely controlling the etching parameters, mushroom structures with diameter of 3 μm and circular centre distance of 8 μm were prepared. The mushroom structure not only achieves super-repellent from high surface tension water (72.8 mN/m) to ultra-low surface tension perfluorohexane (10 mN/m), but also achieves complete rebound even to the high-speed impact of liquid droplets, including water droplets with an impact height of 7.9 cm and perfluorohexane with a height of 3 mm. This fabrication technology helps to build a robust superomniphobic surface for use in harsh environments such as high-speed droplet impacts.