Nanoparticle collection during femtosecond laser micromachining

• Metal nanoparticle collector consisting of a rod electrode and gas suction line. • Recovery of metal nanoparticles during laser micromachining is assessed. • Pulsed laser interactions with ejected material influence recovery efficiency. • Laser fluence dependant dynamics of ejected nanoparticles affect material recovery. • Dependency of material composition on collection efficiency is observed. Femtosecond pulsed laser micromachining is a technique where material is ablated from a surface to produce desired structures. This process generates nanoparticles, which in industrial settings become trapped in a particulate air filter. This work focused on recovering nanoparticles at the point of ablation. The goal was to optimize operating settings for a nanoparticle collector consisting of a rod-shaped electrode contained in a tube that is connected to a suction line. For a fixed laser fluence, three suction flowrates and stage velocities were considered to determine optimal collection parameters. Using copper as an initial target, the collection efficiency was determined by comparing the masses of collected and ablated material. We found that the highest stage velocity led to the best collection efficiency due to reduced interaction between laser pulses and the expanding nanoparticle plume. An intermediate suction flowrate was found to be optimal, balancing attraction of the plume with effective collection. The effect of laser fluence was also investigated. Fluence-dependent dynamics of ejected material led to disparities in collection efficiency. The effect of target material composition was investigated by comparing the collection of pure metals and alloys. A dependency of the collection efficiency on the material composition was observed.