Molecular Dynamics of Ionic Transport and Electrokinetic Effects in Realistic Silica Channels

Abstract

Silica is one of the most widely used inorganic materials in experiments and applications involving aqueous solutions of biomolecules, nanoparticles, etc. In this paper, we construct a detailed atomistic model of a silica interface that captures the essential experimentally known properties of a silica interface. We then perform all-atom molecular dynamics simulations of a silica nanochannel subjected to either an external pressure or an electric field and provide an atomistic description of ionic transport and both electro-osmotic flow and streaming currents for a solution of monovalent (0.4 M NaCl) as well as divalent (0.2 and 1.0 M CaCl 2) salts. Our results allow a detailed investigation of ζ-potentials, Stern layer conductance, charge inversion, ionic mobilities, as well as continuum theories and Onsager relations. We conclude with a discussion on the implications of our results for silica nanopore experiments and micro- and nanofluidic devices.