Cake formation in the filtration of associative microgel suspensions

In this work, we investigate the jamming behavior of associative microgel suspensions used as fluid loss additives in model porous media. We first construct a phase diagram using drying experiments, followed by characterization of the suspensions' rheology and the permeability of the filter cakes at maximum microgel concentration. Microfluidic devices are designed for frontal and lateral flow filtration with pore sizes comparable to or slightly larger than the microgel particles. Microscopic observations reveal irreversible aggregation as the particles pass through pores, leading to cake formation inside and at the exit of the pores-contrary to the classical view of cake formation. Flow in linear channels of similar pore size, however, does not cause jamming, suggesting that extensional shear plays a crucial role. We hypothesize that extensional flows promote the association of hydrophobic groups by unfolding dangling chains, resulting in low-permeability filter cakes with self-adaptive properties for larger pore networks.