Femtosecond laser-induced hierarchical micro/nanostructures of stainless-steel mesh for oil–water separation and detection of high concentration hydrogen

A common method to control the surface wettability of materials is to construct various hierarchical micro/nanostructures followed by surface modification. The femtosecond (fs) laser-induced nanostructures with different morphologies combined with surface modification techniques can be used to adjust the wettability of stainless-steel mesh (SSM). Different micro/nanostructures can be induced by adjusting the fs laser processing parameters, such as laser energy density and scanning interval, transforming the intrinsic slightly hydrophobicity of SSM to hydrophilicity. The hydrophilic surface of fs laser treated-SSM (Fs-SSM) can be used for light oil–water separation with a separation rate of up to 99.64%. Without complex processes and toxic modifiers, the combination of polydimethylsiloxane (PDMS) vapor deposition technology can transform the hydrophilic surface into a hydrophobic surface, achieving the heavy oil–water separation with an average separation efficiency of 99.82%. Moreover, the surface of Fs-SSM coated with palladium (Pd) nanoparticles can be converted from hydrophobic to hydrophilic in hydrogen environment using Pd thermal evaporation coating technology. Upon re-exposure to air, the hydrophobicity of the surface can be restored. This work introduces inventive method to fabricate low-cost, energy-efficient and eco-friendly oil–water separation mesh, while also providing a visual means of detecting higher concentrations of hydrogen.