Laser Ablation of Metal Substrates for Super-hydrophobic Effect

Pulsed UV laser ablation is applied to fabricate super-hydrophobic surfaces on metal substrates. The spike shape micro-structure arrays achieved by the laser ablation on the brass substrates increase the surface roughness (R-a) from similar to 400 nm to similar to 5 mu m. Meanwhile, plenty of nano-structures (200 similar to 600 nm) are also formed and scattered on the surface of the micro-structures. It is found that the water contact angle of the brass substrate increases from 110 degrees to 161 degrees. Super-hydrophobic property of the metal surfaces with both the micro- & nano-roughness is explained by water repellent model for double roughness structures. High speed camera imaging is used to analyze water droplet dynamics during its rolling down along the slanted super-hydrophobic brass surface. It shows that the pulsed laser ablation is a versatile approach to create large area super-hydrophobic surfaces for industrial applications.