Double-functionalization of water repellence and anti-reflectance by multiple-laser-based fabrication of triple-scale hierarchical surface structures

A novel strategy of laser ablation followed by tungsten-based pulsed laser deposition was proposed and experimentally verified for available surface functionalization with superhydrophobicity and anti-reflectance on 316L stainless steel. Three surface patterns, crater, parallel lines (PL), and grid, were manufactured by nanosecond laser ablation, while the surface morphology was controlled by the transverse traverse index. After the pulsed laser deposition treatment, tungsten particles and clusters were densely coated on the laser-ablated surfaces. The fabricated substrates were characterized by triple-scaled hierarchical structures having different patterns, corrugated structures, and broccoli-like nano-protrusions. An aging treatment was performed to improve wettability. The results verified that the proposed multiple laser treatments in combination with the aging treatment allow the quick implementation of superhydrophobicity while maintaining good reflectance over the spectral range. Moreover, the topology was characterized using an optical profiler and through scanning electron microscopy, while a video-based optical contact angle measuring device and spectrophotometer were used to measure the contact angle and optical reflectance, respectively. X-ray photoelectron spectroscopy was performed to analyze the chemical components. This method can prepare water-repellent anti-reflectance hybrid substrates for industrial and academic applications.