Hierarchical composite structure to simultaneously realize superior superhydrophobicity and anti-reflection

Superhydrophobicity and anti-reflection of metallic surfaces have potential applications, and obtaining superhydrophobicity on metallic surfaces by simple methods is still a challenge. The composite microstructure consisting of micro-protrusions, micro-lumps and particles was fabricated on aluminum surface by laser ablation. A layer of hydrophobic species that can prevent the surface from being wetted formed on the microstructure through organic adsorption. In particular, laser ablation parameters were optimized to achieve better superhydrophobicity and anti-reflection. The fabricated superhydrophobic surfaces showed contact angles > 165° for water and contact angles > 160° for high-concentration solutions and high-viscosity solutions. Conventional bounce contact time < 10 ms was exhibited for water droplets impacting on fabricated surfaces, especially, the shortest contact time reaching 9.4 ms. anti-reflection was also realized on the laser-ablated aluminum surface, and specular reflections were almost completely avoided by laser ablation structures. The mechanism of the transition from superhydrophilic to superhydrophobic on fabricated surfaces was discussed. Superhydrophobic aluminum surfaces with anti-reflection could be efficiently manufactured in a few hours without special equipment and harsh condition through the proposed two-step method.