Durable and robust transparent superhydrophobic glass surfaces fabricated by a femtosecond laser with exceptional water repellency and thermostability

Superhydrophobic self-cleaning glass surfaces with good transparency and robustness have diverse applications such as in windshields for automobiles, windows, anti-fouling mirrors, safety glasses, and solar panels. Superhydrophobicity requires high surface roughness, which inevitably results in the loss of surface transmittance. To resolve this contradiction, herein, we report a novel approach using an ultrafast laser direct-writing-dispersed micro-pit array to provide basic roughness, guarantee sufficient unprocessed surface area for high transparency, introduce multiple-laser processing within each pit to induce maximized nano-structure roughness, and then to hydrophobize the surface with a layer of fluoroalkylsilane molecules to achieve good superhydrophobicity. Moreover, distributed periodic micropits with self-organized micro-nano rods, nano-ripples, and nanoparticles were fabricated on silica glass. The glass surfaces show superhydrophobicity with a static contact angle (SCA) of 161° with a 4 μL water droplet, a sliding angle (SA) lower than 2° with a 5 μL water droplet, and transparency over 92% in the visible and near-infrared light. By various robust durability tests, we confirmed that these transparent superhydrophobic glass surfaces exhibited persistent water repellency after being soaked in water for at least 168 h, strong impact resistance of water impinging beyond 9 kg for half-an-hour, and thermal stability up to 500 °C. We report a simple and efficient approach to achieve large-area transparent superhydrophobic self-cleaning glass surfaces with excellent robustness and durability that show great application potential in related areas. Self-cleaning transparent glass surfaces with periodic micro-nano structures fabricated by a femtosecond laser exhibit exceptional water repellency and thermostability.