Bioinspired photocatalytic hedgehog coating for super liquid repellency

Abstract

Super liquid repellency towards highly wetting liquids is of great interest for fundamental research and practical applications. Superomniphobic coatings have been made by forming re-entrant or doubly re-entrant morphologies that result in contact angles above 150° and contact angle hysteresis below 10°. While existing superomniphobic coatings rely on stringed nanoparticles to make re-entrant geometries, we show that a new type of superomniphobic surface is made by microscale hedgehog particles that combine the features of springtail inspired re-entrant microspheres with cicada wing inspired nanoneedles. Such a bioinspired hedgehog coating shows super liquid repellency from water to low surface tension liquids like dodecane with a surface tension of 25.3 mN m⁻¹. The hedgehog particles provide re-entrant structures and the nanoneedles minimize the local liquid–solid adhesion due to the presence of air gaps. Moreover, we use a one-step approach to make scalable titanium dioxide hedgehog coatings with photocatalytic properties. Thus, the photocatalytic hedgehog coating can be easily converted to slippery liquid-infused porous surfaces under ultraviolet illumination in one-step. Such a photocatalytically activated slippery surface shows an ultralow contact angle hysteresis (≤1°) to highly wetting fluids with surface tensions as low as 16 mN m⁻¹.