Investigating the microenvironments of inhomogeneous soft materials with multiple particle tracking

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(under construction) Original entry: Ian Burgess, Fall 2009


M. T. Valentine, P. D. Kaplan, D. Thota, J. C. Crocker, T. Gisler, R. K. Prud'homme, M. Beck, D. A. Weitz, "Investigating the microenvironments of inhomogeneous soft materials with multiple particle tracking," Phys. Rev. E, 64, 061506(9) (2001).


Microrheology, mean-square displacement, Brownian motion


This article describes a new particle tracking technique that allows localized probing of individual microenvironments in inhomogeneous soft materials. Their technique applies passive microrheology to a large ensemble (~100) of fluorescent-labeled particles. They simultaneously track the motion of each particle using video microscopy. The parallelism of this technique allows them to collect much data about several different types of microenvironments in the system in a short amount of time. The limitation of this technique is that the measured particle trajectories are too short to make statistically meaningful comparisons between individual particles, due to the fixed field of view. To overcome this obstacle, the authors group particles whose mean-square displacements are statistically indistinguishable and then combine the data within each group to gain more accurate statistics about each environment. To demonstrate the effectiveness of their technique, the authors apply it to three different types of media. First, a glycerol/water mixture, which should behave as a homogeneous viscous fluid, is used as a standard. The other media studies are agarose, which is an inhomogeneous and porous gel, and F actin, a component of cellular cytoplasm.