Unfolding the rheology and microstructure of bidisperse soft jammed suspensions under shear flow

Soft particle glasses (SPGs) are yield stress fluids that consist of deformable particles that are jammed at volume fractions above the random close packing of equivalent hard sphere suspensions. SPGs flow when they are under stresses that are larger than their dynamic yield stress. These features allow them to be used in various applications such as cosmetic products, coatings, and pastes. However, these suspensions show a glassy structure at low shear rates and transform into a layered phase at high shear rates when the particle size distribution is narrow. In this study, a series of bidisperse suspensions are considered, and the relationship between the microstructure and macroscopic rheology is probed using particle dynamics simulations. Results show that at high shear rates, bidisperse suspensions exhibit a glassy structure when the number ratio of big to small particles is between 0.1 and 0.2, and the ratio of big to small radii is between 1.60 and 1.70. In this regard, a comprehensive phase diagram based on the applied shear rate, particle size ratio, and the ratio of the radii in shear flow is provided. These results provide an alternative method to control the phase behavior of the soft suspensions compared to the conventional understanding which requires a broad particle size distribution.