Does Fluid Flow Impact the Stability of a Colloidal Gel?
Many industrial systems require micron-sized particles (colloids) to remain suspended in a liquid medium, e.g., pesticides, beauty products, and paints. It is undesirable to have these suspensions phase separate or to have the colloids sediment to the bottom/cream to the top. Phase-separation and sedimentation may be arrested by introducing strong, short-ranged attractions through the addition of polymers. The interactions cause the colloids to become "stuck" to each other and form a space-spanning network structure that offers some protection against gravitational and shear stresses.
In this presentation, we introduce an experimental and numerical model system, by which we can study colloidal gel collapse –– the eventual break-down of the suspension's stability under the influence of gravity. The detailed microscopy analysis performed in the group of Prof. Wilson Poon at the University of Edinburgh makes it clear that fluid flow plays an important role in determining the stability of colloidal gels. This inspired us to perform detailed simulations accounting for hydrodynamic interactions between the colloids via the lattice-Boltzmann algorithm to gain a better understanding of the physics. We will show that fluid flow impacts the stability of the gel and that we can capture many of the experimental observations using our simulations, but that there is also a lot of subtlety that requires further analysis.