Effects of Flight Distance on Metal Microdroplet Depositing Behaviors in Laser-Induced Forward Transfer

Laser-induced forward transfer (LIFT) presents promising perspectives towards high precision three-dimensional metal microstructure fabrication. However, the positional deviation of deposits produced in LIFT reduces the printing resolution. In this study, we experimentally investigate the effects of flight distance on the depositing behaviors of the metal droplets in LIFT. A series of droplet deposition experiments with different flight distances were performed, printing a large number of particles in each set of parameters to avoid random errors. Morphology of deposited particles under different conditions was compared. Positional information was extracted by the image matching algorithm. The flight distance was optimized by analyzing the positional deviation and the morphology of particles. The results demonstrate that the positional deviation of particles increases linearly with the flight distance, while the average size of particles is constant. Excessive flight distance increases the oxidation of copper droplets. For the distance less than 20 μm, a portion of particles disappears in the array. There is a flat surface on the top of particles, indicating that droplets have been squashed by the carrier substrate. This conjecture is confirmed by the observation of residual metal particles on the carrier substrate. This study will advance the understanding of droplet generation and the application of LIFT in the industry.