Two-Point Microrheology of Inhomogeneous Soft Materials

John C. Crocker; M. T. Valentine; Eric R. Weeks; T. Gisler; P. D. Kaplan; A. G. Yodh; D. A. Weitz

doi:10.1103/PhysRevLett.85.888

Two-Point Microrheology of Inhomogeneous Soft Materials

John C. Crocker, M. T. Valentine, Eric R. Weeks, T. Gisler, P. D. Kaplan, A. G. Yodh, and D. A. Weitz

Phys. Rev. Lett. 85, 888 – Published 24 July 2000

Abstract

We demonstrate a novel method for measuring the microrheology of soft viscoelastic media, based on cross correlating the thermal motion of pairs of embedded tracer particles. The method does not depend on the exact nature of the coupling between the tracers and the medium, and yields accurate rheological data for highly inhomogeneous materials. We demonstrate the accuracy of this method with a guar solution, for which other microscopic methods fail due to the polymer's mesoscopic inhomogeneity. Measurements in an F-actin solution suggest conventional microrheology measurements may not reflect the true bulk behavior.

Received 10 November 1999

DOI:https://doi.org/10.1103/PhysRevLett.85.888

Authors & Affiliations

John C. Crocker^1,*, M. T. Valentine^1,†, Eric R. Weeks^1,‡, T. Gisler², P. D. Kaplan³, A. G. Yodh¹, and D. A. Weitz^1,§

¹The Department of Physics and Astronomy, The University of Pennsylvania, 209 S. 33rd Street, Philadelphia, Pennsylvania 19104
²Universität Konstanz, Fakultät für Physik, P.O. Box 5560, 78457 Konstanz, Germany
³Unilever Research, 45 River Road, Edgewater, New Jersey 07020

^*Present address: Applied Physics, Caltech, Mail Code 128-95, Pasadena, CA 91125.
^†Present address: Physics Department and DEAS, Harvard University, Cambridge, MA 02138.
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