A numerical study of AC electroosmosis

Abstract

AC electroosmosis is the process in which fluid flows are induced by oscillating electric fields. When the ions in the fluid have different sizes or valencies, applying an oscillating field can give rise to non-zero average fields called Asymmetric Rectified Electric Fields(AREFs). We study the properties of AREFs in a one dimensional system of two planar electrodes. We use Numerical methods to solve the Poisson-Nernst-Planck equations and measure the average electric potential as a function of system size, driving frequency, driving amplitude, and the valencies and diffusivities of the ions. If diffusivities are unequal but valencies are not, we find that the average potential scales with the square of the driving frequency in the low frequency regime. We also find that the potential changes sign at a particular frequency related to the system size. If valencies are unequal but diffusivities are not, the sign change persists, but the potential stays constant at low frequencies. The constant value taken increases with the driving amplitude and valency difference.