(102f) A Quantitative Study of Bulk Stresses in Nonlinear Microrheology

We investigate the nonlinear microrheology of a simple model system - a spherical probe translating through a dilute suspension of rigid rods - to elucidate a variety of issues inherent in the interpretation of nonlinear microrheology. We have developed a computational system to quantitatively examine the issues present when examining bulk stresses in nonlinear microrheology, as originally discussed by Squires (Langmuir, 2008). Previous nonlinear microrheology theory has concentrated on the dramatic direct microstructural deformation, but recent work has emphasized the importance of the microstructural behavior in the bulk (Sriram et. al, 2009). Following this work, we focus our attention on the bulk microstructural deformation, and examine the significance of its (Lagrangian) transient nature, as well as the consequences of the mixed and inhomogeneous flows inherent to nonlinear microrheology. From this quantitative study, we pose solutions for the current theoretical issues facing nonlinear microrheology in interpretation and comparison of the microviscosity and the shear viscosity obtained from traditional bulk rheometry.