Using oscillatory shear to tune the viscosity of shear thickening suspensions

When concentrated colloidal suspensions are under stress, their viscosity can increase by over an order of magnitude. These shear thickening suspensions have many interesting technological applications but are also extremely difficult to process in an industrial setting due to the strong dependence of the flow properties on the shear rate. Previous work has shown that the viscosity of these suspensions can be tuned by applying fast orthogonal perturbations to the system. This behavior, however, was only demonstrated for a few values of applied stress and one suspension volume fraction. We are using a custom built attachment to a standard Anton Paar rheometer, to extend these previous measurements to various volume fractions, applied stresses, and system sizes. In this talk, I will describe our results which show that dethickening due to orthogonal shear is volume dependent, and a non-monotonic dependence on the primary applied strain rate. Understanding these trends has consequences for applications involving shear thickening fluids ranging from 3D printing to the processing of cement.