(463f) How Bulk Liquid Viscosity Shapes Capillary Suspensions

Capillary suspensions feature networks of liquid bridges between colloidal particles suspended in two immiscible liquids. The formation of this network allows the design of novel materials with exceptional and tunable mechanical properties. However, to advance in the design of new materials, it is imperative to understand the role of liquid viscosity in shaping these suspensions.

Using experiments and numerical simulations, we investigated the effect of viscosity of the bulk liquid on the structure and rheological behaviour of capillary suspension in the pendular state. To modulate the viscosity of the bulk fluid, we employed different ratios of either dodecane and diisononyl phthalate, or silicone oils with varying chain lengths as bulk liquids. Intriguingly, rheological measurements revealed that higher bulk liquid viscosity reduces strength and flexibility in capillary suspensions, which is partly attributed to a reduced inter-connectivity of the capillary-driven percolating network. This is caused by the breakup of liquid bridges occurring at shorter distances in the presence of highly viscous bulk liquids, as indicated by numerical simulations.