Jet ejection of inelastic and elastic non-Newtonian fluids by laser-induced shockwave*

Controlled ejection of fluids with relatively high viscosity or non-Newtonian properties is of great recent interest for printing-electronics, 3D-manufacturing or bioprinting applications. However, traditional nozzle printing methods are limited to low viscous fluids, otherwise problems of clogging or jamming may occur. In this contribution we investigate jet ejection of two non-Newtonian polymeric solutions with similar shear-thinning behaviour, but different inelastic (xanthan-gum 0.35 wt%) and elastic (sodium polyacrylate 0.4 wt%) properties by using a nozzle-free method based in a shockwave laser-induced technique (Tagawa et al. 2012, Delrot et al. 2016). Results of jet speed versus shockwave cavitation bubble energy, and jet speed against time of the non-Newtonian solutions are compared with similar results using a glycerin/water mixture of 100 cSt. We demonstrate that jets generated with the inelastic solution (XG) evolve into drop formation comparable to glycerin/water jets, whereas for the elastic solution (SPA) jets experience a retraction after ejection. These observations indicate a strong dependence on the different extensional flow properties of the non-Newtonian fluids under consideration.