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Optical coherence tomography velocimetry in controlled shear flow.
1Biological Physics, School of Physics and Astronomy, University of Manchester, Oxford Rd., Manchester M139PL, United Kingdom.
Summary
Doppler-shift optical coherence tomography (OCT) precisely maps fluid flow, revealing wall slip in margarine and shear banding in polyacrylamide solutions. This technique probes tiny volumes of complex fluids, even opaque ones.
Area of Science:
- Rheology
- Fluid Dynamics
- Optical Physics
Background:
- Complex fluids exhibit unique flow behaviors like wall slip and shear banding.
- Understanding these behaviors is crucial for material science and industrial applications.
- Traditional methods struggle to probe the microscale velocity profiles of opaque or concentrated fluids.
Purpose of the Study:
- To develop and validate a Doppler-shift optical coherence tomography (OCT) technique for mapping velocity profiles in complex fluids.
- To investigate the flow behavior of concentrated solutions and opaque materials under shear.
- To observe phenomena such as wall slip and shear banding at a microscale level.
Main Methods:
- Utilized Doppler-shift OCT with a 1300-nm infrared source for non-invasive velocity profiling.
- Integrated the OCT system with a plate-plate rheometer for controlled shear flow experiments.
- Probed small sample volumes (3.4 picoliters) to generate 2D velocity flow field maps.
Main Results:
- Successfully measured velocity profiles in concentrated colloidal suspensions and margarine.
- Observed distinct wall slip phenomenon in margarine samples.
- Detected shear banding in polyacrylamide solutions, indicating non-uniform flow.
Conclusions:
- Doppler-shift OCT is a powerful tool for characterizing complex fluid rheology at the microscale.
- The technique enables visualization of intricate flow behaviors like wall slip and shear banding in opaque materials.
- This advancement offers new possibilities for studying material properties and optimizing formulations.
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