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.