(320d) Numerical Simulations of Traveling Wave Electroosmosis At Nanoscale

We developed a mathematical model describing traveling-wave electroosmotic micropumps to explain their rather poor ability to work against pressure loads. Unlike most of the authors, we use the combination of the Poisson-Nernst-Planck and the Navier-Stokes equations, without common simplifications (e.g., the slip boundary condition for velocity and the thin double layer approximation). The dynamical simulations allow a detail study of the energy transformations and the charging of the electric double layers. Using Matlab and COMSOL Multiphysics, we performed series of extensive parametric studies to determine the dependence of generated electroosmotic flow on the arrangement of the pump and on the characteristics of the driving ac-voltages. The results are consistent with our belief that all ac electroosmotic pumps tested so far were simply too large. According to our findings, the ac electroosmosis is likely to be suitable only at sub-micrometer scale, as the pump's ability to work against pressure loads diminishes rapidly when increasing the channel diameter.