The influence of surface dynamics on electric double layer forces between colloidal surfaces approaching at constant speed

This study deals with the electric double layer repulsive force between two colloidal flat plates, approaching at constant velocity and undergoing surface charge relaxation. In particular, closed form solutions are obtained for the case of low surface potential and ion exchange between surface and Stern layer. A closed form solution is also presented for the case of low potential and finite rate of surface charge dissociation using a perturbation expansion. In the former case, the force between the surfaces upon contact depends on the approach velocity through a relation derived in the present work, whereas in the latter the force at contact always diverges to infinity. Asymptotic results for the force upon contact are also obtained for the general nonlinear case, i.e. for any level of potential. Using these results, an optimized numerical code is developed for the solution of the nonlinear problem. The repulsive force profiles are computed for several cases and discussed.