Wettability/anti-icing properties of hierarchical Micro/nanostructured copper surface prepared by Micro milling and chemical etching

Ice accumulation on the metallic surface usually results in seriously economic losses, resource wastes and even hazard accidents. Superhydrophobic surfaces (SHSs) are recognized as one of the most promising candidates for water repellence and anti-icing, offering both environmental and economic advantages over the traditional methods. The ordered microstructure arrays with controllable parameters play an essential role in mechanism analysis, rational design and reproducible construction of SHSs. However, the efficient fabrication of ordered microarrays on metal substrates with high resolution and high accuracy is still fraught with significant challenges. Here, a multilevel micro/nano surface with rectangular micropillars was fabricated on copper substrate by the integration of micro milling and chemical etching, which exhibits superior superhydrophobicity with water contact angle of 171.1 ± 1.5° and sliding angle of 2.2 ± 0.7°. The developed deburring scheme makes an outstanding contribution to the in-situ removal of milling burrs generated on the top of micropillars. The variation in surface wettability with microarray geometry and etching conditions indicates that a favorable surface morphology is crucial for improving the water repellency of the surface. The results of the durability experiment and the self-cleaning test demonstrate the robust comprehensive stability of the prepared SHSs against moisture, high temperature and mechanical wear, as well as the superior fouling resistance against solid and liquid contaminants, which is mainly ascribed to the hierarchical micro/nanostructures. Moreover, the present micro/nanostructures are also demonstrated to be capable of enhancing the delayed icing performance of the copper surface, with the freezing time of a 5 μL water droplet being 519.86 ± 13.53 s. Meanwhile, the superhydrophobic copper surfaces exhibit remarkable anti-icing behavior against saline solutions, as evidenced by the freezing time of 1078.42 ± 31.24 s for a 5 μL NaCl droplet. This work provides a sustainable and high-precision approach for the fabrication of metal-based SHSs, expecting to advance the theoretical research and industrial applications of anti-icing functional surfaces.