Hyper-anti-freezing bionic functional surface to -90°C

Freezing phenomenon has troubled people for centuries, and efforts have been made to lower the liquid freezing temperature, raise the surface temperature, or mechanical deicing. Inspired by the elytra of beetle, we demonstrate a novel functional surface for directional penetration of liquid to reduce icing. The bionic functional surface is fabricated by projection microstereolithography (PµSL) based three dimensional printing technique with the wettability on its two sides tailored by TiO2 nanoparticle sizing agent. A water droplet penetrates from the hydrophobic side to the superhydrophilic side of such a bionic functional surface within 20 ms, but it is blocked in the opposite direction. Most significantly, the penetration time of a water droplet through such a bionic functional surface is much shorter than the freezing time on it, even though the temperature is as low as -90°C. This work opens a gate for the development of functional devices for liquid collection, condensation, especially for hyperantifogging/freezing.