A mobile drop-on-demand laser-assisted printing head integrated with a robotic arm and a target tracking system

We present a mobile drop-on-demand (DoD) printing system based on laser-induced side transfer (LIST). By replacing the bulky free-space optics used in previous LIST configurations with a fiber-based laser delivery system, we developed a compact printing head and integrated it as an end-effector onto a robotic arm. Using model inks with viscosities up to 165 cP and time-resolved imaging, we investigated printability, printing dynamics, and the effect of printing head-to-substrate distance on key printing quality metrics. We found that printing quality deteriorates significantly beyond a 3 mm standoff distance. To address motion-induced printing quality loss on dynamic substrates, we integrated a custom-built fiber-optic distance sensor that actively maintains a constant standoff distance in real time. This enabled high-quality printing on moving targets simulating physiological motion. Additionally, we characterized the influence of ink viscosity and laser energy on droplet formation dynamics and ejected volume. Our results demonstrate the feasibility of motion-compensated, laser-assisted DoD printing in dynamic environments, with potential applications in intraoperative tissue engineering.