Alternating Current Electroosmotic Micropumping Using A Square Spiral Microelectrode Array

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Moore, Thomas Allen
MEMS , micropump , ACEO , microfluidics , electrokinetics , electrohydrodynamics
An alternating current electroosmotic micro pumping device has been designed, experimentally tested and theoretically analyzed using an electrohydrodynamic theoretical model applied to a computer simulation model. The device SP-1 is a microelectrode array which uses the principal of AC electroosmosis (EO), ions driven along microelectrode surfaces by coulomb forces produced by tangential electric fields. These ions, when driven, induce a net fluid motion due to viscous drag forces. Three submerged microelectrode wires were deposited on a substrate using microfabrication techniques such that a square spiral geometry was formed. Device SP-1 received asymmetrically applied AC signals creating a travelling wave of potential and resulted in a net fluid flow across the microelectrode array. Microsphere tracer particles were suspended in ethanol to measure the fluid velocity to determine pumping performance and the experimental operating frequency at which maximum fluid velocity is achieved. The experimental results were reviewed and at an AC signal frequency of 125 Hz, device SP-1 was capable of pumping ethanol at a fluid velocity of approximately 270 μm/s. The experimental results were in good agreement with the theoretical predictions produced using the computer simulation model. In addition, the computer simulation model predicted a similar flow profile to those previously predicted and experimentally observed. Overall, novel micropumping device SP-1 was found to produce a net flow comparable to previously tested devices and a computer simulation framework capable of analyzing future micropump design concepts was developed.
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