Original Entry: Ian Burgess, Fall 2009 (currently under construction)
Microrheology is a form of rheology in which the properties of a complex fluid are measured with microscopic spatial precision by tracking the movement of a small, micron-sized, particle embedded in the fluid.
In passive microrheology, Brownian motion of the particle due to thermal energy is observed. The viscoelastic modulus of a complex fluid <math>G(\omega)</math> can be determined from the mean square displacement <math>\<\delta r^2\></math> of the tracer particle undergoing thermal motion. Mason and Weitz showed that