Rheological Microscopy: Local Mechanical Properties from Microrheology

D. T. Chen, E. R. Weeks, J. C. Crocker, M. F. Islam, R. Verma, J. Gruber, A. J. Levine, T. C. Lubensky, and A. G. Yodh

Phys. Rev. Lett. 90, 108301 – Published 14 March 2003

Abstract

We demonstrate how tracer microrheology methods can be extended to study submicron scale variations in the viscoelastic response of soft materials; in particular, a semidilute solution of $λ$ -DNA. The polymer concentration is depleted near the surfaces of the tracer particles, within a distance comparable to the polymer correlation length. The rheology of this microscopic layer alters the tracers’ motion and can be precisely quantified using one- and two-point microrheology. Interestingly, we found this mechanically distinct layer to be twice as thick as the layer of depleted concentration, likely due to solvent drainage through the locally perturbed polymer structure.

Received 25 September 2002

DOI:https://doi.org/10.1103/PhysRevLett.90.108301

Authors & Affiliations

D. T. Chen¹, E. R. Weeks², J. C. Crocker³, M. F. Islam¹, R. Verma¹, J. Gruber¹, A. J. Levine⁴, T. C. Lubensky¹, and A. G. Yodh¹

¹Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, Pennsylvania 19104
²Department of Physics, Emory University, Atlanta, Georgia 30322
³Department of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104
⁴Department of Physics, University of Massachusetts, Amherst, Amherst, Massachusetts 01003

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Vol. 90, Iss. 10 — 14 March 2003

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