Printability and Extensional Rheology of Polymer Solutions

Free-surface flows – jetting, spraying, atomization during fuel injection, roller-coating, gravure printing, nanoimprint hot embossing, several microfluidic drop/particle formation techniques, and screen-printing – all involve the formation of axisymmetric fluid elements that spontaneously break into droplets by a surface-tension-driven instability.  The growth of the capillary-driven instability and pinch-off dynamics are dictated by a complex interplay of inertial, viscous and capillary stresses for simple fluids. Additional contributions by elasticity, extensibility and extensional viscosity play a role for complex fluids. Using experiments and theory,  we elucidate how polymer composition, flexibility, and molecular weight as well as  coil-stretch transition determine the thinning and pinch-off dynamics, and thus influence printability, spinnability, sprayability and jettability of polymeric complex fluids.