Three-dimensional AC electroosmotic micropump with high power density

Abstract

This paper presents a novel three-dimensional alternating current electroosmosis (ACEO) micropump with high power density. ACEO is a phenomenon to generate a flow of a liquid such as water by applying an AC voltage to the liquid. Using a specific configuration, a net flow due to ACEO becomes unidirectional and an ACEO micropump can be constructed. Many ACEO micropumps have been proposed; however, most of them are of the planar type, and their output power per device volume is not sufficiently high for applications such as micro fluid power sources for micro total analysis systems, lab-on-a-chips, biomedical microelectromechanical systems (bio-MEMSs), soft microactuators, and soft microrobots. To achieve a higher output power density, in this study, we proposed an ACEO micropump using an array of plate-cylinder electrodes, which is called PC-ACEO-MP. To induce unidirectional flow efficiently, a square pole-slit electrodes ACEO micropump called SS-ACEO-MP has been proposed using asymmetrical pillar-shaped electrodes. PC-ACEO-MP is an extension of SS-ACEO-MP with a three-dimensional structure. First, the finite element method simulations were performed and the results showed that PC-ACEO-MP has the potential to realize high output power with a 1 cm3 effective pump volume using large numbers of plate-cylinder electrodes connected in parallel and in series. Second, a fabrication method using MEMS fabrication process, including electroplating, was proposed and developed for a micro-holed electrode plate that forms parallel cylinder electrodes. The validity of the proposed process was confirmed by fabricating large models and micro-models of the micro-holed electrode plate. The diameter and number of microholes were 10 μm and 36 100, respectively, for the large models and 3 μm and 65 500, respectively, for the micro models. Finally, PC-ACEO-MPs were constructed and their promising pumping characteristics were clarified through experiments using deionized water. The estimated power density was approximately 400 times higher than that of the former high output power ACEO micropump.