Two-step approach for the fabrication of transparent and superhydrophobic surfaces using a stable fluoride-free nanosilica solution

We present a new method to fabricate transparent superhydrophobic surfaces by a facile two-step approach using low-cost and environmentally friendly materials. First, a highly stable and fluorine-free nanosilica solution was synthesized by a simple sol-gel method. Subsequently, the nanosilica solution was sprayed on the surface of transparent glass or poly (ethyleneterephthalate) (PET) substrates to obtain the special coating with a transparent and superhydrophobic surface. The as-prepared nanosilica solution exhibited long-term room-temperature stability. The average size of the nanosilica particles was approximately 30 nm and the particles’ surface was covered with a large number of hydrophobic functional groups. In addition, the superhydrophobic surface exhibited a visible light transmittance above 50% at 600 nm, which was dependent on the coating thickness. The water contact angle (WCA) exceeded 150°, and the sliding angle was less than 10°. Furthermore, the superhydrophobic surface exhibited self-cleaning properties owing to its water repellency. In addition, the superhydrophobic surface exhibited good durability, and the water jet experiment had no significant effect on its anti-wetting and self-cleaning properties. Moreover, short-term water jet testing did not noticeably affect the anti-wetting and self-cleaning properties of the superhydrophobic surface. In contrast, sustained water jet treatment led to nanosilica detachment from the coating, resulting in diminished hydrophobic performance.