Numerical investigation on the effect of the in-situ photopolymerization of coalescence behavior of non-Newtonian polymer drops*

The post-deposition kinetics of the drops play a crucial role in the morphology and hence the quality of the printed structure created using any of the droplet-based printing processes such as inkjet printing, aerosol jet printing (AJP), electrohydrodynamic jet printing (EHD), etc. For 3D printing of photo-curable materials, such post-deposition kinetics include the interplay between impact, spreading, coalescence, and photo-induced curing of the deposited drops. In this study, we employ direct numerical simulations to probe the coalescence behavior, of two non-Newtonian, polymeric drops in the presence of photocuring UV radiation. Coalescence dynamics, which is quantified by the time evolution of the height (h) and width (W) of the growing bridge formed by coalescing drops, is investigated for different photo-curing conditions seen in the aerosol jet printing (AJP) process. Further, we compare this complex thermo- fluid-solutal behavior of the coalescing drops by tracking the evolution of the curing front inside the photocuring drops.