Experimental Characterization of an EHD Ion-Drag Micropump for Cryogenic Micro-Pumping Applications

This paper presents a study on the characterization of a planar multi-stage electrohydrodynamic (EHD) ion-drag micropump for pumping of liquid nitrogen. Four designs of the pump — consisting of different emitter configurations (planar and saw-tooth), emitter-collector spacings (20 and 50 microns), and gaps between successive electrode pairs (80, 100 and 200 microns) — were tested at DC voltages ranging from 0 to 2.5 kV. The generated electric currents and static pressure heads were measured to characterize the pumping performance. After collecting and processing the data for the various designs, it was evident that the purity of the liquid plays a vital role in the repeatability of the pumping results. In all cases high-purity liquid nitrogen was used. The complex interaction between the liquid and the electrodes along with the probabilistic nature of the ion-generation process sometimes prohibited achieving the same pumping performance under identical voltage levels, thus purity of the nitrogen used was very important. The highest pressure head (30 Pa at 1700 V) was generated with a (50,100,s) design. The (50,100,s) stands for saw-tooth emitters and planar collectors, 50 μm inter-electrode spacing, and 100 μm electrode-pair spacing.