Dynamic Sealing Using Magnetorheological Fluids

Abstract

Micropumps are microfluidic components that are widely used in applications such as chemical analysis, biological sensing, and microrobots. However, one obstacle in developing micropumps is the extremely low efficiency relative to their macroscale counterparts. This paper presents a dynamic sealing method for external gear pumps to reduce the volumetric losses through the clearance between the tips of gears and the housing by use of magnetorheological fluids. By mitigating these losses, we are able to achieve high efficiency and high volumetric accuracy with current mechanical architectures and manufacturing tolerances. Static and dynamic sealing using magnetorheological fluids are investigated theoretically and experimentally. The Mason numbers Mn(p) and Mn(Ω), which are defined in terms of the pressure gradient of the flow and the velocity of the moving boundary, respectively, are used to characterize and evaluate the sealing performance. A range of magnetic field intensities is explored to determine optimal sealing effectiveness, where effectiveness is evaluated with the ratio of volumetric loss and the friction factor. Finally, we quantify the effectiveness of this dynamic sealing method under different working conditions for gear pumps.