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http://hdl.handle.net/1721.1/35772
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| Title: | The Flexure-based Microgap Rheometer (FMR) |
| Authors: | Clasen, Christian
Gearing, Brian P.
McKinley, Gareth H. |
| Keywords: | Shear rheometry
Yield stress
Emulsion
Microrheometry
Microrheology
Wall slip
Mayonnaise
Complex fluid
Gap-dependent rheology |
| Issue Date: | 23-Jan-2007 |
| Series/Report no.: | 06-P-10 |
| Abstract: | We describe the design and construction of a new microrheometer designed to facilitate the viscometric study of complex fluids with very small sample volumes (1-10 μl)and gaps of micrometer dimensions. The Flexure-based Microgap Rheometer (FMR) is a
shear-rate-controlled device capable of measuring the shear stress in a plane Couette
configuration with directly-controlled gaps between 1 μm and 200 μm. White light
interferometry and a three-point nanopositioning stage using piezo-stepping motors are used to control the parallelism of the upper and lower shearing surfaces which are constructed from glass optical flats. A compound flexure system is used to hold the fluid sample testing unit between a drive spring connected to an ‘inchworm’ motor and an independent sensor spring. Displacements in the sensing flexure are detected using an inductive proximity sensor. Ready optical access to the transparent shearing surfaces enables monitoring of the structural evolution in the gap with a long working-distance video-microscope. This configuration then allows us to determine the microgap-dependent flow behavior of complex fluids over 5 decades of shear rate. We demonstrate the capability of the FMR by characterizing the complex stress and gap dependent flow behavior of a typical microstructured food product (mayonnaise) over the range of gaps from 8 to 100 μm and stresses from 10 to 1500 Pa. We correlate the gap-dependent rheological response to the microstructure of the emulsion and changes induced in the material by prolonged shearing. |
| Description: | Submitted to J. Rheol. |
| URI: | http://hdl.handle.net/1721.1/35772 |
| Appears in Collections: | HML Preprints (for all years)
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| 06-P-10.pdf | | 1111Kb | Adobe PDF | View/Open |
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