Direct writing of three-dimensional Cu-based sensors using femtosecond laser reduction of CuO nanoparticles

2D and 3D metal microstructures are directly written using femtosecond laser reductive sintering of metal oxide nanoparticles. CuO nanoparticle solutions including CuO nanoparticles, a reductant agent, and a dispersant, were coated on glass substrates. Then, focused femtosecond laser pulses were irradiated onto the solution film to write the microstructures in air. Finally, non-irradiated CuO nanoparticles were removed. Cu-rich and Cu₂O-rich microstructures were selectively fabricated by controlling the laser irradiation conditions. We demonstrated direct-writing of 2D and 3D Cu-based microstructures using femtosecond laser-induced reduction of CuO NPs. Using respective appropriate femtosecond laser conditions, 3D Cu-rich microstructures were obtained by a combined process of the dispensing coating and laser irradiation. The Cu-rich hot-film flow sensor which had microbridge structure, were successfully produced. This direct-writing technique is useful for fabricating various sensors on arbitral shaped substrates in air.