Development of an Electrohydrodynamic Injection Micropump for Cryogenic Cooling

Abstract

Cryogenic cooling has become a widely adopted technique to improve the performance of electronics and sensors. A potential application of an electrohydrodynamic (EHD) pumping system is its use in pumping fluids in cryogenic cooling systems. In this paper we present the results of a theoretical/experimental investigation to study the feasibility of using an EHD injection micropump for pumping liquid nitrogen. First, the mechanisms of charge transport and ionization phenomenon in cryogenic liquids are discussed. Next, the design and fabrication of an EHD injection micropump that employs an array of interdigitated saw-tooth/plane electrodes are described. Finally, experimental results and observations are presented. An asymmetric saw-tooth/plane geometry was designed to achieve strong inhomogeneous electric field. Each saw-tooth had a base length of 10 μm with a tip angle of 60°. The gap between emitter and collector electrodes was 20 μm and the distance between each stage (a pair of emitter and collector electrodes) from neighboring stage was 40 μm. The dimensions of the patterned area were 10 mm by 20 mm allowing approximately 300 stages to be fabricated along the length of the micropump. The maximum pressure head achieved by this micropump was 550 Pa and 205 Pa for HFE-7100 and liquid nitrogen, respectively.