On the Mechanism of AC Electroosmosis

Abstract

Previously researchers considered ions in electric double layers (EDL) to analyze the phenomenon of alternating current electroosmosis (ACEO). However, they did not give a deep interpretation about the formation mechanism of ACEO and their theories cannot explain some experimentally observed phenomena. In this paper, we propose a physical model to analyze the formation mechanism of ACEO by considering ions both in EDL and in solution. It is found that the ions in solution play an important role in ACEO, and by considering the effect of ions both in EDL and in solution, we can reasonably explain some phenomena, including flow reversal at high frequency (typically 10-100 kHz) and inapplicability of ACEO at high salt concentration (above 30 μM), which existing theories cannot give convincing explanations. We also use Navier-Stokes equation to theoretically analyze the ACEO and it is found that the flow reversal can be predicted by our concepts in certain conditions.