Spraying pressure-tuning for the fabrication of the tunable adhesion superhydrophobic coatings between Lotus effect and Petal effect and their anti-icing performance

Abstract

The tunable adhesion behavior of superhydrophobic surfaces has received much attention due to its unique properties to control the wetting state of water droplets. Herein, we report a facile and scalable spraying pressure-tuning method to control surface morphology by adjusting the spraying pressure to fabricate the tunable adhesion superhydrophobic coating (TASC). The superhydrophobic suspension prepared by fluorinated epoxy resin and polytetrafluoroethylene particles is sprayed on the glass substrate by altering the spraying pressure between 0.25 bar and 2.0 bar to control surface morphology, line profile, and surface roughness of TASCs. The water contact angles of TASCs are greater than 150°, while the water sliding angles of these surfaces are found from 2.6° (Lotus effect) to 180° (Petal effect) with the decrease of spraying pressure, which are attributed to the transformation of the wetting state on their surface from Cassie-Baxter state to Cassie impregnating state caused by the change of line profile and the decrease of surface roughness. We have proved that TASCs with different spraying pressure can be used in the droplet transportation, selection, and microreaction platform. Furthermore, the anti-icing performance of TASCs with different surface morphology and roughness was investigated by the freezing time and the ice adhesion strength. TASC-2.0 exhibited excellent anti-icing performance with freezing time at 392 s and the ice adhesion strength at 51 kPa than TASC-0.25 exhibited relatively flat surface, which is attributed to the air pocket captured by rough structure to reduce the solid/liquid contact area and has great potential for anti-icing applications.