Glass surface micromachining with simultaneous nanomaterial deposition by picosecond laser for wettability control

Glass surface micromachining with simultaneous redeposition of nanomaterials in the vicinity of machined microscale trenches is achieved using a picosecond laser of visible wavelength in ambient air. After investigating the spatial distribution of redeposited nanomaterials by a unit discrete laser micromachining line, multi-line patterns machined with variable interline separations are characterized using optical and scanning electron microscopes. For large interline separations, laser machined debris was redeposited in the form of web-like nanofibrous aggregates with significant spatial variation in density. Reduced separations improved spatial uniformity but the increased material density induced noticeable conversion from web-like nanofibrous to fractal-like nano-cauliflower structures. In this way, picosecond laser machining processes enabled a single-step fabrication of multi-hierarchical micro/nanostructures on arbitrary glass surface areas with tunable nanomaterial structures. Based on the wetting behavior on patterned surfaces in ambient air by using the patterned surfaces as Wilhelmy plates in force-displacement measurements and in-situ optical microscope inspection, we find that contact angle hysteresis is suppressed for surfaces patterned with sufficiently small line separations due to the water infusion in the deposited nanomaterials. The studied laser processing method can be potentially employed for fast and effective fabrication of liquid infused surfaces with complex microscale patterns combined with controllable nanofeatures.