A dual-functional surface with hierarchical micro/nanostructure arrays for self-cleaning and antireflection

Surfaces with hierarchical micro/nanostructures have been widely fabricated for their extensive applications in self-cleaning, antireflection, etc. However, a flexible and highly efficient method for obtaining such surfaces remains a great challenge, especially for metals. In this paper, we propose a simple and tunable approach for fabricating a dual-functional surface with patterned hierarchical micro/nanostructure arrays. A femtosecond laser was used to remove the SiO₂ thin film, coated on the Cu substrate, masklessly and selectively. Then the arrays of micro-protrusions decorated with nanoneedles were synthesized successfully through thermal oxidation. We demonstrate that the morphology of the micro-protrusions remarkably affects the surface properties, which can be flexibly tuned by controlling femtosecond laser parameters. By optimizing the laser parameters (e.g. scanning mode and laser fluence), we can achieve high performances with respect to superhydrophobicity, with a maximum contact angle of 161° and extremely low adhesion with a minimum sliding angle of less than 1.7°, thus demonstrating its self-cleaning function. In addition, antireflection properties with a minimum reflectance of less than 1% at a wavelength range of 700-800 nm can be achieved and the total reflectance can be steadily below 6% over a broad wavelength range of 600-1150 nm.