Multiparticle tracking to study the local environment of heterogeneous media

Microrheology has been successfully applied to study the local viscous and elastic properties of numerous polymer systems, but fails to accurately measure bulk properties for heterogeneous media. Many techniques, by using only ensemble-averaged quantities or data from a single probe, fail to provide even local information. We use a multi-particle tracking technique to study a highly elastic agarose gel and an F-actin solution. We find that by retaining both ensemble-averaged and individual probe particle statistics, we can extract information about the local visco-elasticity and the details of the heterogeneity.