Spatially resolved quantitative rheo-optics of complex fluids in a microfluidic device
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Mckinley_Spatially resolved.pdf
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Author(s)
Ober, Thomas Joseph
Soulages, Johannes
McKinley, Gareth H.
Date Issued
August 2011
Journal
Journal of Rheology
Publisher
Society of Rheology
Citation
Ober, Thomas J., Johannes Soulages, and Gareth H. McKinley. Spatially Resolved Quantitative Rheo-optics of Complex Fluids in a Microfluidic Device. Journal of Rheology 55, no. 5 (2011): 1127.
Version
Author's final manuscript
Abstract
In this study, we use microparticle image velocimetry (μ-PIV) and adapt a commercial birefringence microscopy system for making full-field, quantitative measurements of flow-induced birefringence (FIB) for the purpose of microfluidic, optical rheometry of two wormlike micellar solutions. In combination with conventional rheometric techniques, we use our microfluidic rheometer to study the properties of a shear-banding solution of cetylpyridinium chloride (CPyCl) with sodium salicylate (NaSal) and a nominally shear-thinning system of cetyltrimethylammonium bromide (CTAB) with NaSal across many orders of magnitude of deformation rates (10-2 ≤ math ≤ 104s-1). We use μ-PIV to quantify the local kinematics and use the birefringence microscopy system in order to obtain high-resolution measurements of the changes in molecular orientation in the wormlike fluids under strong deformations in a microchannel. The FIB measurements reveal that the CPyCl system exhibits regions of localized, high optical anisotropy indicative of shear bands near the channel walls, whereas the birefringence in the shear-thinning CTAB system varies more smoothly across the width of the channel as the volumetric flow rate is increased. We compare the experimental results to the predictions of a simple constitutive model, and we document the breakdown in the stress-optical rule as the characteristic rate of deformation is increased.
MIT Department
Massachusetts Institute of Technology. Department of Mechanical Engineering
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DOI of Published Version
https://doi.org/10.1122/1.3606593
