Direct Observation of Flow-Concentration Coupling in a Shear-Banding Fluid

Matthew E. Helgeson, Lionel Porcar, Carlos Lopez-Barron, and Norman J. Wagner
Phys. Rev. Lett. 105, 084501 – Published 19 August 2010
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Abstract

We present the first direct evidence of flow-concentration coupling in a shear-banding fluid using the first measurements of scanning narrow-aperture flow ultrasmall-angle neutron scattering. Transmission measurements in the flow-gradient shear plane determine the spatial concentration profile of the material. Shear banding in a model fluid composed of wormlike micelles near an equilibrium isotropic-nematic transition is shown to be concomitant with shear-induced demixing, providing new insight into the nonequilibrium phase behavior of the fluid. The new experimental approach and analysis apply generally to any fluid, and will enable more rigorous testing of theories for shear-banding and shear-induced phase separation.

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  • Received 16 May 2010

DOI:https://doi.org/10.1103/PhysRevLett.105.084501

© 2010 The American Physical Society

Authors & Affiliations

Matthew E. Helgeson1, Lionel Porcar2, Carlos Lopez-Barron3, and Norman J. Wagner3

  • 1Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge Massachusetts 02139, USA
  • 2Institut Laue-Langevin, BP 156, F-38042 Grenoble Cedex 9, France
  • 3Center for Neutron Science, Department of Chemical Engineering, University of Delaware, Newark Delaware 19716, USA

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Issue

Vol. 105, Iss. 8 — 20 August 2010

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