In this study, we characterize the shear and extensional rheology of dilute to semidilute solutions of cellulose in the ionic liquid 1-ethyl-3-methylimidazolium acetate (EMIAc). In steady shear flow, the semidilute solutions exhibit shear thinning, and the high-frequency complex modulus measured in small amplitude oscillatory shear flow exhibits the characteristic scaling expected for solutions...

Polymeric liquid bridges are known to fail during extension. This phenomenon of failure seemingly calls into question the operating principle filament stretching rheometers. In these devices, a polymeric sample is initially placed between two plates. The then stretched bridge by moving plates apart in specified way. We here show that steady extensional viscosity can be measured if separated suc...

We show that visualization and analysis of capillary-driven thinning and pinch-off dynamics of the columnar neck in an asymmetric liquid bridge created by dripping-onto-substrate can be used for characterizing the extensional rheology of complex fluids. Using a particular example of dilute, aqueous PEO solutions, we show the measurement of both the extensional relaxation time and extensional vi...

Numerical optimization of a “six-arm cross-slot” device yields several three-dimensional shapes fluidic channels that impose close approximations to an ideal uniaxial (biaxial) stagnation point extensional flow under the constraints having four inlets and two outlets (two outlets) for Newtonian creeping flow. One numerically designed geometries is considered suitable fabrication at microscale, ...

A precision-machined cross-slot flow geometry with a shape that has been optimized by numerical simulation of the fluid kinematics is fabricated and used to measure the extensional viscosity of a dilute polymer solution. Full-field birefringence microscopy is used to monitor the evolution and growth of macromolecular anisotropy along the stagnation point streamline, and we observe the formation...

The extensional rheological properties of dilute polymer solutions play a dominant role in many commercial processes such as air-assisted atomization. This is a high deformation rate process important in application of diverse materials such as paints, fertilizer sprays and delivery of airborne drugs. Dilute polymeric solutions which have identical values of high shear-rate viscosity (HSV) ofte...

A precision-machined cross-slot flow geometry with a shape that has been optimized by numerical simulation of the fluid kinematics is fabricated and used to measure the extensional viscosity of a dilute polymer solution. Full-field birefringence microscopy is used to monitor the evolution and growth of macromolecular anisotropy along the stagnation point streamline, and we observe the formation...

Microfluidic devices are ideally suited for the study of complex fluids undergoing large deformation rates in the absence of inertial complications. In particular, a microfluidic contraction geometry can be utilized to characterize the material response of complex fluids in an extensionally-dominated flow, but the mixed nature of the flow kinematics makes quantitative measurements of material f...