ABSTRACT
Electro-osmosis, one of the main electrokinetic effects, is the process by which an ionized liquid moves with respect to a stationary-charged surface under the action of an external electric ‰eld. The electro-osmotic phenomenon was ‰rst observed by Reuss [1] from an experimental study on clay diaphragms. In the mid-nineteenth century, Wiedemann [2] repeated the experiment and formally introduced the mathematical theory behind it. Although the electro-osmotic phenomenon has been known for more than 200 years, the application of electro-osmotic ow was only limited to the ‰eld of analytical chemistry to transport samples in capillaries. However, recent developments in microelectromechanical systems have made a breakthrough progress toward using electro-osmotic ows in complex microuidic networks for pumping liquids [3-5]. Because of the ability of pumping a wide range of working uid, this nonmechanical pumping has become an attractive uid handling method in the emerging “lab-on-a-chip” microuidic devices for sample loading, mixing, ushing, and reagent transporting [6,7]. In the last decades, there have numerous analytic [8-12], numerical [13-16], and experimental [17-19] studies on electrokinetic microows.
