Superhydrophobicity vs. Ice Adhesion: The Quandary of Robust Icephobic Surface Design

The mesoscale, multitier texture of the lotus leaf has served as an inspiration to fabricate surface designs with controllable superhydrophobic properties, targeting a broad range of applications. The choice of material for such designs is directly related to surface performance, in particular under adverse and realistic conditions. Due to its importance in many applications, here aluminium is employed as a material platform and identify key porous hierarchical textures, yielding extraordinary impalement‐resistant behavior: Droplet repellency is demonstrated consistently for water impact velocities up to 12 m s−1 (extreme Weber number, We ≈ 3500). Despite impressive superhydrophobic behavior, if ice forms on such surfaces, ice adhesion is markedly stronger than on less hydrophobic alumina nanotube array structures. In a departure from the findings of the well‐accepted shear stress‐based ice adhesion criterion, a deviation between decreasing ice adhesion strength and increasing hydrophobicity is observed. This is explained with ice adhesion mechanism, depending strongly on the applied stress field orientation and the respective effective ice–substrate contact area. Our results indicate that ice adhesion criteria for the performance of icephobic surfaces should account for the simultaneous presence of shear and tensile stresses, instead of shear stresses alone. Aluminum‐based porous hierarchical nanotextures feature extremely high anti‐impalement properties (up to Weber numbers of ≈3500). However, for the same surface, where ice adhesion strength is low in the presence of shear stress alone, ice adhesion is significantly higher if normal and shear stresses co‐exist (as they frequently do in practical applications).