A study on the impact of liquid metal droplets onto metal and elastomer substrates

The diffusion and dynamic behaviors of liquid metal droplet during impact significantly affect its application in 3D printing and painting processes. To obtain a better understanding of the impact process of liquid metal droplets, we analyze the influence of different initial conditions and substrate materials on droplet spreading, impact force, and elastic wave propagation on the substrate. It is found that an agglomeration phenomenon can be observed when the liquid metal droplets impact onto a soft elastomer substrate, which is not observed as a metal substrate is employed. Regardless of the substrate material, when surface tension dominates the diffusion, the diffusion factor of droplets is proportional to \(\sqrt{We}\) (Weber number). It is also observed that the self-similarity of liquid metal droplet impact force on copper substrates, which is not the case for soft elastomer substrates. Using smoothed particle hydrodynamics (SPH) simulations, the time-domain curve and peak point of the droplet can be well predicted for a metal substrate. Furthermore, by recording the acceleration signal on the substrates, we further obtain the energy radiated by elastic waves, providing an explanation for energy conversion during the impact process with varying parameters. The results provide an additional understanding on the complex impact behaviors of liquid metal droplets.