Optimized Cross-Slot Flow Geometry for Microfluidic Extensional Rheometry
Author(s)Haward, Simon J.; Alves, Manuel A.; McKinley, Gareth H.; Oliveira, Monica S. N.
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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 of a strong and uniform birefringent strand when the dimensionless flow strength exceeds a critical Weissenberg number Wi[subscript crit]≈0.5. Birefringence and bulk pressure drop measurements provide self-consistent estimates of the planar extensional viscosity of the fluid over a wide range of deformation rates (26 s[superscript -1]≤ε˙≤435 s[superscript -1]) and are also in close agreement with numerical simulations performed by using a finitely extensible nonlinear elastic dumbbell model.
DepartmentMassachusetts Institute of Technology. Department of Mechanical Engineering
Physical Review Letters
American Physical Society
Haward, Simon J. et al. “Optimized Cross-Slot Flow Geometry for Microfluidic Extensional Rheometry.” Physical Review Letters 109.12 (2012). © 2012 American Physical Society
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