Superhydrophobic surface with good mechanical robustness and stable Cassie-Baxter state throughout freezing and thawing processes

Constructing superhydrophobic surfaces has emerged as a promising anti-icing approach in recent years. However, the water droplets on the superhydrophobic surfaces are readily able to transition from the low-adhesion Cassie-Baxter (CB) state to the high-adhesion Wenzel state during the freezing process. Furthermore, the micro/nano structures of superhydrophobic surfaces are vulnerable to damage from mechanical loads. It remains a significant challenge to develop a robust superhydrophobic surface that can maintain the Cassie-Baxter state throughout the freezing and thawing processes. Herein, a micro-papilla/nano-particle (MPNP) structured superhydrophobic surface with good mechanical robustness and anti-icing property was prepared on aluminum substrate through laser ablation followed by spinning. The MPNP structure provides higher micro-features, denser nano-features, and a thicker hydrophobic layer, thereby endowing the surface with higher heat resistance, larger energy barrier, and Laplace pressure for water impaling in rough structures . Consequently, the MPNP surface exhibits excellent anti-icing property with a 6-fold prolongation in freezing delay time and a ∼6-fold reduction in de-icing force in comparison to the bare Al substrate, and the droplet on this surface can maintain the CB state with mere 4.6 %/4.0 % decline in contact angle and 18.7 %/7.1 % increment in contact diameter in the freezing/thawing process. Moreover, owing to the protecting effect of the micro-papillae on the nano-particles, the thicker hydrophobic layer, and the interlock effect between the hydrophobic layer and rough structure, the MPNP surface can maintain super-hydrophobicity after a seize of mechanically robustness tests.