Simulation and experiments on colloidal particle capture in a shear field

Using a colloidal particle scattering apparatus, we have observed shear-dri ven formation of particle doublets near a wall for latex and emulsion syste ms. For the latex system, capture is in the expected stable downstream posi tion. For the emulsion system, capture occurs upstream from the fixed parti cle. Furthermore, the frequency of capture is found to depend on pH in agre ement with rheology results. Computer simulations have been performed to ex amine the criteria for capture in this case, and, of necessity, a novel pot ential is introduced. Good comparison can be obtained between simulation an d experiment when surface charge variations linked to pH are invoked as the key variable.