Femtosecond laser processing for multi-functional hierarchical micro/nano structures on curved surfaces

• Multifunctional multi-scale micro/nano composite structures (exhibiting superhydrophobic and anti-reflective properties) were successfully fabricated on curved surfaces using a 3D femtosecond laser processing system. • The processed area of the Al cylinder appeared deep black, displaying an average diffuse and specular reflectance of 6.90 % and 0.31 %, respectively, in the spectrum band from 400 nm to 2500 nm, demonstrating excellent anti-reflective properties. • The average of the contact angle measured in the raw area of the Al cylinder was 78.9°, while the processed area was 164.2°, the material underwent a transition from hydrophilic to superhydrophobic after laser irradiation . In this study, we developed a three-dimensional (3D) femtosecond laser processing platform to fabricate micro/nano structures with both anti-reflective and superhydrophobic functions on curved components. The experimental findings demonstrate the fabrication of hierarchical structures, comprising micro-scale structures, subwavelength structures, and nanoparticles, on metal surfaces following femtosecond laser ablation. Particularly, the average diffuse and specular reflectance of the processed surface in the spectrum band (400 nm to 2500 nm) was quantified at 6.90 % and 0.31 %, respectively, markedly lower than the 83.44 % and 64.66 % values observed on the pristine smooth surface. Moreover, the average contact angles measured on the pristine and processed areas were found to be 78.9° and 164.2°, respectively, and the sliding angle of processed areas was 4.8°. The wettability of laser-processed samples changed from hydrophilic to superhydrophobic with the duration of placement, which was related to carbon adsorption on the surface. The anti-reflective and superhydrophobic properties of the micro/ nano structures showed minimal alteration following abrasion tests, demonstrating excellent mechanical durability. These findings highlight the precise fabrication of multifunctional hierarchical micro/nano composite structures on curved components using the 3D laser processing methods and parameters detailed herein.