Optimized Cross-Slot Flow Geometry for Microfluidic Extensional Rheometry
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...
| Main Authors: | , , , |
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| Other Authors: | |
| Format: | Article |
| Language: | en_US |
| Published: |
American Physical Society
2013
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| Online Access: | http://hdl.handle.net/1721.1/79062 https://orcid.org/0000-0001-8323-2779 |
| Summary: | 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. |
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