Ultrafast Processing of Hierarchical Nanotexture for a Transparent Superamphiphobic Coating with Extremely Low Roll-Off Angle and High Impalement Pressure

Abstract

Low roll-off angle, high impalement pressure, and mechanical robustness are key requirements for super-liquid-repellent surfaces to realize their potential in applications ranging from gas exchange membranes to protective and self-cleaning materials. Achieving these properties is still a challenge with superamphiphobic surfaces, which can repel both water and low-surface-tension liquids. In addition, fabrication procedures of superamphiphobic surfaces are typically slow and expensive. Here, by making use of liquid flame spray, a silicon dioxide–titanium dioxide nanostructured coating is fabricated at a high velocity up to 0.8 m s⁻¹. After fluorosilanization, the coating is superamphiphobic with excellent transparency and an extremely low roll-off angle; 10 µL drops of n-hexadecane roll off the surface at inclination angles even below 1°. Falling drops bounce off when impacting from a height of 50 cm, demonstrating the high impalement pressure of the coating. The extraordinary properties are due to a pronounced hierarchical nanotexture of the coating.

Superamphiphobic surfaces can repel both water and oils. Impalement pressure and mechanical stability are still challenges. Fabrication is typically slow or expensive. Using liquid flame spraying, an up-scalable method is demonstrated for fabricating SiO₂/TiO₂ nanostructured coatings at a velocity of 0.8 m s⁻¹. After fluorosilanization, the coating shows extremely low roll-off angles even toward n-hexadecane, high impalement pressure, and good transparency.

http://ift.tt/2t1Bma2