Beyond Micro-/Nanostructures: Close-Packed Nanostructure Enables Superior Superhydrophobic Anti-Icing Coatings

Hierarchical micro-/nanostructures have long been regarded as the optimal architecture for superhydrophobic anti-icing surfaces. Here, by constructing superhydrophobic coatings with identical surface chemistry but distinct microscopic architectures, we directly compare the anti-icing performance of a close-packed nanostructure and a hierarchical micro-/nanostructure. Surprisingly, the close-packed nanostructure consistently outperforms its hierarchical counterpart in static/dynamic superhydrophobicity at room temperature and icing environments, freezing delay, ice adhesion reduction, and freeze/de-icing cycling stability, etc. Mechanistic investigations reveal that the close-packed nanostructure generates a higher Laplace-pressure barrier against water penetration, suppresses contact-line pinning, and minimizes interfacial energy dissipation during droplet impact. In contrast, micro-grooves within the hierarchical micro-/nanostructure act as preferential pathways for water infiltration, promoting Cassie-to-Wenzel transitions and interfacial adhesion in icing environments. Moreover, the nanostructured coating maintains robust superhydrophobicity and low ice adhesion after mechanical abrasion, tape-peeling and long-term outdoor exposure, etc. These findings challenge the long-standing "hierarchical-is-better" paradigm and identify the close-packed nanostructure as a more effective structural strategy for durable superhydrophobic anti-icing surfaces, providing new design guidelines for next-generation passive icephobic materials.