Superhydrophobic surface with excellent mechanical robustness, water impact resistance and hydrostatic pressure resistance by two-step spray-coating technique

Superhydrophobic surfaces (SHSs) exhibit outstanding liquid-repellent properties, attracting numerous attentions from both academia and industry. However, their weak mechanical robustness and poor water impact resistance still limit their practical applications. Herein, SHSs were fabricated by a simple and scalable two-step spray-coating technique, i.e., spray-coating micro-particles as bottom layer, followed by spray-coating nanoparticles onto the micro-particles as top layer; both micro- and nano-features were firmly affixed by low-surface-energy polymer binder. By carefully tuning the micro-particle ratio in bottom layer and mixed solvent ratio in top layer, we obtained the optimized micro/nano- hierarchical structures, which offered the SHSs super-repellence to various liquids (e.g., water, blood and honey) and excellent mechanical robustness to cloth wipe, eraser rub, multi-cycled sandpaper abrasion and tape peel-off. The SHSs withstood high-speed droplet impact and water jet impact with water impact speed of up to ~9.5 m/s (corresponding to ~3760 of Weber value). In addition, they maintained the superhydrophobicity under a hydrostatic pressure of 0.1 MPa for more than one month, or 3 MPa for more than 12 h, which is the highest record ever reported.