Microrheology is a tool that is seeing increasing interest in fields involving complex and biological materials. The various methods that are collected under the microrheology umbrella have shown themselves to be useful in studying heterogeneous systems at the microscopic level, providing both average and local property information. As with macroscopic measurements, microrheology measurements are dependent upon the validity of certain assumptions. For example, particle-tracking microrheology, in which the motion of a colloidal ‘tracer' particle is used to infer system properties, assumes that the tracer particle does not interact with the material being studied other than as a hard object. Thus, for example, the tracer cannot chemically react with the medium, nor should it be attracted to (or conversely, repelled by) the substance it is submerged in. The effect of such ‘extra' interactions upon microrheology measurements is therefore a matter for concern.

Results are presented from various sets of Brownian Dynamics simulations used to simulate particle-tracking microrheology experiments in a dilute polymer solution. The effects of including tracer-medium interactions are also addressed.