title: Effects of electrostatic correlations on electrokinetic phenomena.
abstract: The classical theory of electrokinetic phenomena is based on the mean-field approximation that the electric field acting on an individual ion is self-consistently determined by the local mean charge density. This paper considers situations, such as concentrated electrolytes, multivalent electrolytes, or solvent-free ionic liquids, where the mean-field approximation breaks down. A fourth-order modified Poisson equation is developed that captures the essential features in a simple continuum framework. The model is derived as a gradient approximation for nonlocal electrostatics of interacting effective charges, where the permittivity becomes a differential operator, scaled by a correlation length. The theory is able to capture subtle aspects of molecular simulations and allows for simple calculations of electrokinetic flows in correlated ionic fluids. Charge-density oscillations tend to reduce electro-osmotic flow and streaming current, and overscreening of surface charge can lead to flow reversal. These effects also help to explain the suppression of induced-charge electrokinetic phenomena at high salt concentrations.
authors.affiliation: Franklin W. Olin College of Engineering, Needham, Massachusetts 02492, USA.
authors.forename: Brian D
authors.initials: BD
authors.lastname: Storey
authors.forename: Martin Z
authors.initials: MZ
authors.lastname: Bazant
mesh_terms: D003198:Computer Simulation; D004579:Electron Transport; D052578:Ionic Liquids / Q000737:chemistry*; D007477:Ions / Q000737:chemistry*; D007700:Kinetics; D008956:Models, Chemical; D012212:Rheology / Q000379:methods*; D055672:Static Electricity
chemical_list: D052578:Ionic Liquids; D007477:Ions