Design, fabrication, and testing of an electrohydrodynamic ion-drag micropump

This paper presents the design, fabrication, and testing of a novel electrohydrodynamic (EHD) ion-drag micropump. In order to maximize the electrical field gradients that are responsible for EHD pumping, we incorporated three-dimensional (3-D) triangular bumps of solder as part of the EHD electrodes. To form these bumps, Niobium was sputter-deposited onto a ceramic substrate, coated with photoresist, optically exposed and etched using a reactive ion etcher to define the electrode pattern. The substrate was then "dipped" into a molten solder pool. Since the solder adheres only to the metallic film, bumps of solder form on the electrodes, giving the electrodes a significant 3-D character. The overall dimensions of the micropump are 19 mm x 32 mm x 1.05 mm. Four different designs were fabricated and tested. Static pressure tests were performed with a 3M Thermal Fluid (HFE-7100) as the working fluid and the optimum design was identified. The results with the thermal fluid were highly promising and indicated a pumping head of up to 700 Pa at an applied voltage of 300 V. The experimental results for the four different designs show that the presence of the 3-D bump structures significantly improves the pumping performance. Also, a much better pumping performance was obtained with the micropump in which the emitter had a saw-tooth shape.