The dynamics of colloidal particles in a flowing suspension are determined by their fluid-mediated forces. Each particle’s motion generates long-ranged disturbance flows in the surrounding fluid that entrain both close and distant neighbors, resulting in non-negligible many-body hydrodynamic interactions (HIs). While colloidal HIs have been studied extensively in Newtonian solvents, there are few theoretical or experimental frameworks with which to quantify them in viscoelastic fluid media, such as polymeric solutions.

In this talk, I use fluid mechanical theory and simulation to study hydrodynamic interactions between colloidal particles, supported by optical tweezer experiments. First, I show that measurements of particle rotations with optical tweezers in Newtonian solvents accurately report fluid disturbances with exquisite precision, enabling sensitive quantification of many-body HIs. Experiments are then conducted in polymer solutions. For which, I develop analytical and computational models to describe the dynamics of colloidal particles in viscoelastic fluids.

This work advances understanding of colloidal transport and hydrodynamics in complex fluid media, ultimately informing the design of multiphase flows for targeted mechanical performance.