The role of fluid flow and convective steering during the assembly of colloidal crystals

Three-dimensional computations of steady flows directed toward the (1 1 1) plane of a face-centered cubic (fcc) packing of spheres are carried out to assess the convective steering hypothesis, which posits that solvent flow could play a role in the assembly of colloidal crystals. The computations clearly show the kinematics of flows into and through the packing and clarify the influences of fluid inertia and particle arrangement. Results from the computations accurately describe the outcome of macroscopic experiments and are consistent with a network model applied to the microscopic, colloidal system. For the geometry considered here, flows are predicted to direct over 20% more fluid into selected positions along the surface of the packing and reinforce the tendency for ordering newly growing layers with fcc symmetry.