A study on an AC electroosmotic micropump using a square pole - Slit electrode array

The paper presents a novel AC electroosmotic micropump using a square pole - slit electrode array called the SS-ACEO-MP. The AC electroosmosis (ACEO) generates convection flows when AC voltage is applied to a liquid such as water with fixed electrodes. The ACEO flow is stable without electrolysis due to the low AC voltage; however, to realize a micropump for wide applications, a special mechanism for a unidirectional flow is required. For that purpose, conventional devices utilize asymmetric electrodes, induced-charge electroosmosis, and traveling wave voltage. For practical applications, high slip velocity due to ACEO is required. The proposed pump consists of a square pole - slit electrode array, and efficiently generates a total flow by the slip velocity mainly on the slit electrodes. The proposed pump features a simple pillar-shaped structure without moving parts, efficient flow generation, and easy improvements of the pressure and the flow rate due to the arrayed structure. First, 3D FEM (finite element method) simulation of the SS-ACEO-MPs was performed and the characteristics were clarified. The size parameters that maximize the effective slip velocity under no load were clarified. Second, the SS-ACEO-MPs were fabricated by a MEMS (micro electro mechanical systems) fabrication process that included electroforming. Third, experiments on the SS-ACEO-MPs were performed. The characteristics of the SS-ACEO-MPs were clarified. Finally, at the applied voltage of 26 Vpp, the maximum effective slip velocity of 1.6 mm/s was realized with a unit size of 0.2 × 0.2 × 0.05 mm3.