(221e) Theory and Experiments of Measuring Microrheology Via Dynamic Magnetic Susceptibility

Microrheological measurements provide knowledge that conventional rheological measurements cannot, such as the mechanical properties at the microscopic length scale and the general heterogeneity of the medium. Furthermore, microrheological experiments require only microliters of samples, which is favorable with expensive materials. A typical microrheological experiment tracks the motions of probing particles and later relates the rheological properties with these motions. We introduce a novel technique, the magnetic resonance spectroscopy of Brownian relaxation (MSB), that utilizes magnetic nanoparticles as probes and relates the rheological properties with the magnetic responses. This technique is favorable with in vivo measurements of samples where the motions of particles are not easily visualizable. In this study, we build the relations between magnetic responses and simple constitutive models of viscoelastic fluids, and we use these relations to investigate the rheological properties of samples that are measured by MSB.