High-temperature imprinting and superhydrophobicity of micro/nano surface structures on metals using molds fabricated by ultrafast laser ablation

Abstract

Micro/nano surface structures show great significance in both fundamental research and practical applications. Imprinting technique is widely used to fabricate micro/nano surface structures on polymers at low temperature, but barely implemented on metals. In this paper, femtosecond (fs) laser was used to fabricate micro/nano surface structures on tungsten (W), which served as molds for subsequent solid state imprinting process to replicate the counter structures onto copper (Cu) surface at temperature up to 1000°C. Nano-ripples superimposed on micro-bumps array are fabricated without surface oxidation, and the height of the micro-bumps is adjustable by varying the laser energy input for W molds preparation. The as-prepared Cu surface structures are hydrophobic and turn to superhydrophobic after chemical modification. To demonstrate the feasibility and capability of this technique, similar surface structures were fabricated on A356 aluminum alloy (A356 AA) by liquid state imprinting at 740°C using M2 steel molds prepared by picosecond (ps) laser ablation. This approach combines the advantages of ultrafast laser ablation to fabricate molds with micro/nano surface structures and high-temperature imprinting process to replicate the micro/nano structures onto target metallic surfaces. It opens new possibility for the mass fabrication of functional micro/nano surface structures on metals.