Generation of Liquid Metal Microdroplets for Extreme Ultraviolet Source Target using Eccentric Droplet Collision

To meet the requirements of applications such as extreme ultraviolet (EUV) sources for droplet trains with small diameters, large spacing, and high sphericity, this work proposes a method to generate micron-scale droplet trains by precisely controlling the eccentric collisions of liquid-metal droplets in a two-dimensional plane. The formation of monodisperse satellite droplet trains resulting from eccentric binary collisions of Ga–In–Sn alloy droplets is systematically investigated. A critical eccentricity model applicable to low Ohnesorge number (Oh) conditions is developed, which enables accurate prediction of the stretching-separation threshold. A non-monotonic, single-peak dependence of ligament volume and length on eccentricity is revealed, and a unified scaling relationship is established. Consequently, stable monodisperse satellite droplet trains are achieved with small diameters (～20 ± 2 μm), large spacing (～200 ± 5 μm), and high repetition rates (～18–43 kHz), satisfying the specifications for EUV droplet targets.