Deposition-on-contact regime and the effect of donor-acceptor distance during laser-induced forward transfer of viscoelastic liquids

Optimizing the direct-writing of viscoelastic liquids requires an understanding of the governing physics during jet and droplet formation. In this article, we study the effect of the distance between the donor and acceptor surfaces and identify a unique deposition-on-contact regime associated with viscoelasticity. For a given laser pulse energy, depending on the liquid film thickness, rheological properties, and the distance between the liquid film and the acceptor surface, the resulting jet can result in either a rapid deposition of a small volume or the formation of a liquid bridge that delays the breakup of the liquid filament and can result in deposition of multiple droplets. By adjusting the gap distance between the donor and acceptor surfaces, we show that it is possible to obtain single drop depositions via deposition-on-contact from viscoelastic liquids. Using dimensionless parameters, we present criteria that can be used to predict the different regimes observed in the experiments.