Competition after liquid droplet contact on super-cooled surfaces: spreading vs solidification

Additive manufacturing processes are based on liquid droplet solidification after their deposition on super-cooled surfaces. However, the exact processes leading to certain splat properties are yet unknown. Observing spreading hexadecane droplets on super-cooled plates by means of total internal reflection (TIR) imaging allows completely new, temporally and spatially resolved, insights into the solidification patterns and dynamics. Various regimes of solidification are observed, depending on the surface temperature. The total rate of solidification can be theoretically described, based by the Johnson-Mehl-Avrami-Kolmogorov (JMAK) equation. We also quantify the nucleation rate and dendritic growth during the solidification, to investigate the arrest behavior of spreading droplets.