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 32 mm 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.

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This paper describes an ongoing research to evaluate and characterize electrohydro-dynamic (EHD) meso- and micro-pumps for spot cooling of sensors. In the proposed concept, the localized cooling is achieved by means of a flow of liquid nitrogen that is driven by an ion-drag pump towards the heat source, where heat is directly removed. First, a numerical heat transfer model will illustrate the advantages of the proposed concept of spot cooling with liquid nitrogen against a conventional conduction cooling. Next, we will present experimental results for pumping of liquid nitrogen via (EHD) a pump at the meso-scale, as well as experiments with EHD micro-pumps for pumping of HFE-7100 at room temperature. The objective of this research is to establish the optimum operational and design conditions for micro-pumping of liquid nitrogen for spot cooling applications.

Low temperature cooling provides excellent operating conditions for some conventional and superconducting electronics applications. The cooling requirements for these applications include moderate to low power levels (down to fraction of Watts) and very strict spatial and temporal temperature variation (in the order of 0.1K or less). In this paper, experimental and modeling results of a liquid nitrogen cooling system, using an EHD meso pump are presented. The pumping mechanism uses the EHD ion-drag technique. The experimental set-up, procedures and results are presented, followed by a pumping curve obtained by numerical modeling.