Directional motion of water droplets enhances anti-icing failure of structural superhydrophobic surfaces

Abstract

Preventing ice formation on solid surfaces is a crucial concern in various applications, such as aircraft de-icing and protecting electrical transmission cables. One approach to combat ice or frost formation involves the fabrication of superhydrophobic surfaces with micro- or nanostructures. However, some research suggests that the effectiveness of these superhydrophobic surfaces in preventing ice formation may be compromised under conditions of high humidity and low temperatures. Many researchers attribute the resistance of the wetting transition from the Cassie-Baxter state to the Wenzel state on superhydrophobic surfaces to Laplace pressure difference. However, according to molecular dynamics simulations and physical experiments, we find that the impact of Laplace pressure difference depends on the relative size of water droplets and air pockets on the structure. If the size of water droplets is smaller than the characteristic length of the air pockets, directional motion due to Laplace pressure difference and van der Waals force leads to water droplet aggregation and accelerates the ice formation and failure of anti-icing measures. Therefore, our research offers significant insights into the mechanical mechanisms that contribute to the failure of anti-icing techniques on structural superhydrophobic surfaces. This understanding is critical for the design of effective anti-icing or icephobic surfaces.