Durable Organic Coating-Free Superhydrophobic Metal Surface by Paracrystalline State Formation

Abstract

The chemical instability of traditional organically-decorated superhydrophobic metal surfaces is a significant issue, severely limiting practical applications. This is due to the susceptibility of low surface energy coatings to ion permeation, decomposition, and exfoliation, especially in harsh environments. Here, organic coating-free, durable superhydrophobic surfaces on Al alloys by developing the paracrystalline state of a bionic anthill tribe structure is successfully achieved, using femtosecond laser element-doping microstructuring followed by repetitive annealing processes. Remarkably, the inherent superhydrophobic properties of the sample are maintained for ≈2000 h in a corrosive 3.5 wt.% NaCl aqueous solution, significantly surpassing the performance of traditional organic coatings. Moreover, this inherent superhydrophobicity remains nearly unchanged, even after rigorous electrochemical reaction measurements. Additional tests involving UV irradiation (>100 h), freezing cycles (>100 cycles), and acid/alkali resistance (>65 h) further demonstrate that the environmental adaptability of the surface far exceeds that of silane-coated surfaces. Ab initio calculations reveal that the formation of the paracrystalline state reduces surface energy and enhances chemical stability, thereby extending the durability of the superhydrophobic metal. These findings offer a powerful strategy for utilizing atomic-level structural rearrangements to design inherent superhydrophobic surfaces without the need for organic coatings.