ELECTROKINETIC LIFT FORCE FOR A CHARGED-PARTICLE MOVING NEAR A CHARGED WALL - A MODIFIED THEORY AND EXPERIMENT

We present the refined theory of the electrokinetic lift force for a c harged particle moving at a charged wall at the distance much larger t han the double layer thickness. The theory is based on the lubrication approximation for the solution of the Stokes equation for the flow ar ound a long cylinder moving near a solid wall. The ''thin double layer '' approximation is used to solve the ionic balance and electro-osmoti c flow equations. The electrokinetic lift force is then obtained by in tegration of the viscous stress tensor as well as the Maxwell stress t ensor over the particle surface. The resulting lift force for the cyli nder translating, rotating at the wall as well as for the stationary c ylinder in the wall shear how, is considered. Following this, we apply the Derjaguin approximation to transform the obtained results to the sphere-wall geometry and we compare our theoretical predictions with t he measurements of the electrokinetic lift force performed in the ''co lloidal particle collider'' apparatus for the latex particles suspende d in the glycerol-water solutions. Our theoretical results for the ele ctrokinetic lift force exceeds by several orders of magnitude one obta ined from the previously developed theory and are in a good agreement with experimental findings. (C) 1998 Elsevier Science B.V. All rights reserved.