In-situ deposition of oxidized porous metal nanoparticles on the surface of picosecond laser-induced micro/nano structures: A new kind of meta-surface equipped with both super-hydrophobicity and anti-reflectivity

This paper proposes a new kind of composite micro/nano structure composed of porous nanomaterials including titanium (Ti) gradient material and titania (TiO₂) gradient material. The composite structure is fabricated via in-situ deposition of gradiently distributed and oxidized porous titanium nanoparticles on the surface of picosecond laser-induced micro/nano structures. The porous composite layer made up of Ti gradient material and TiO₂ gradient material shows the best anti-reflectivity. The ability of TiO₂ for absorbing –CH₃ hydrophobic group and the air cushion effect of nanostructure endow the TiO₂ gradient porous material with hydrophobic characteristics. Then, the period and height of the desired microstructure of the composite micro/nano structure with the best super-hydrophobicity and anti-reflectivity are confirmed to be about 10 μm and more than 10 μm, respectively. The designed composite micro/nano structures are fabricated using picosecond laser induction processing strategy with the etched depth of the materials being only about 12 μm. The reflectance of the designed composite micro/nano structure is around 2 % from the visible band to the near-infrared band and below 20 % from the ultraviolet to middle-infrared band. Moreover, its slip angle is just 4° and contact angle 167.