SHEAR-INDUCED DEPOSITION OF COLLOIDAL PARTICLES ON SPHEROIDS

The capture of small spheres by large spheroids in a simple shear flow, due to van der Waals attractive forces, was studied theoretically. In the Smoluchowski limit (for which van der Waals attraction cancels hydrodynamic interactions) it was found that for all practical purposes the deposition rate is independent of the orbit constant of the spheroid and becomes independent of axis ratio for axis ratios larger than about 3. For small spheres the deposition rate on spheroids is identical to that on large spheres, with the radius of the sphere replaced by an equivalent radius of the spheroid, based on its volume. Exact calculations, taking hydrodynamic interactions and van der Waals forces into account, show that under these conditions the deposition rate is also independent of orbit constant and, for slender bodies, of axis ratio. The trends in capture efficiency with shear rate and particle size are similar to those for unequalsized spheres. © 1992.