(158a) Particle Tracking Techniques and Their Applications

The tracking of individual particles in a nontrivial flow is a common experimental problem. I will describe how this can be done in a variety of situations, including three-dimensional tracking of thousands of particles simultaneously (in slowly-moving microscopic flows). Free software is freely available at www.physics.emory.edu/~weeks/idl/ . I will also present a variety of applications of these techniques, including microfluidic flows, jamming in complex fluids, and characterization of novel materials using microrheology. The technique of microrheology uses the thermal motion of particles to infer the viscoelastic moduli characterizing a material. For example, by tracking tracer particles in a regular fluid, their diffusion constant can be measured which relates to the fluid's viscosity. In a more complex material, the tracer particle motion over different time scales relates to the moduli at different frequencies.