Multi-jets formation using laser forward transfer

•A silver-nanoparticles ink is transferred by laser using LIFT at high speed.•Multi-jet formation is investigated with a time-resolved imaging technique.•Laser pulses separated by 2μs and 25μm lead to stable jets.•Well-defined, 16μm droplets are printed at a rate of 500,000 droplets/s. The dynamics of multi-jets formation in liquid films has been investigated using the laser-induced forward transfer (LIFT) technique. This technique allows the deposition of micrometer-sized droplets with a high spatial resolution from a donor substrate to a receiver substrate. The donor was a silver nanoparticles ink-coated substrate. The interaction of the laser pulse with the donor ink layer generates an expanding bubble in the liquid which propels a jet towards the receiver. Silver lines have already been printed by depositing overlapping droplets in a “low speed” process. In order to increase the throughput, it is necessary to decrease the time between the depositions of two droplets. By scanning the beam of a high repetition rate UV picosecond laser (343nm; 30ps; 500kHz) with a galvanometric mirror, successive pulses are focused on the silver nanoparticles ink-coated donor substrate. The shape and dynamics of single jets and adjacent jets have been investigated by means of a time-resolved imaging technique. By varying the distance between the laser spots, different behaviours were observed and compared to the printed droplets. A spacing of 25μm between laser spots was found to generate both stable jets and well-controlled, reproducible droplets at high speed.