The effect of melting-induced volumetric expansion on initiation of laser-induced forward transfer

A numerical model was developed to investigate thermal processes that initiate laser-induced forward transfer (LIFT). The model included laser absorption, conduction, melting, and volumetric expansion in a thin film. The model was used to investigate the role of volumetric expansion associated with the melting process and was used to help explain surface deformations observed in previous studies of LIFT. The results of the model indicated that volumetric expansion initiated fluid motion that was directed away from the substrate, and the fluid motion was sufficient to induce surface deformations that remained after solidification. The resulting textured surface was similar to that observed experimentally below the droplet expulsion threshold. The fluid motion away from the substrate may explain the mechanism by which droplet formation occurs.