A Reduced Model for Polymer Pendant Drop Formation and Thinning

Understanding non-Newtonian fluid rheological behavior is essential for both fundamental and practical applications, including lab-on-a-chip devices, inkjet printing, spray coatings, and electrospray systems. This work investigates the formation and thinning of polymer pendant droplets using a simplified model. We develop a one-dimensional numerical model coupled with the Arbitrary Lagrangian Eulerian (ALE) formulation to capture the dynamics of filament thinning and drop formation. To investigate the effects of elasticity, dilute polymeric solutions are utilized and contrasted to a viscous Newtonian fluid. After measuring viscosity and moduli in the linear viscoelastic regime, a small amount of liquid is stretched between pistons to derive elongational properties in the non-linear viscoelastic regime. Taking into account the Ohnesorge and Deborah numbers, sensitivity studies are performed to define a printing domain. The study reveals significant differences in elasto-capillary times between the linear and non-linear regimes, indicating the substantial influence of elasticity on thinning dynamics and stability, thereby paving the way for printing processes to be optimized with both Newtonian and non-Newtonian fluids.