Multistage Viscous Micropumps

The viscous micropump consists of a cylinder placed eccentrically inside a microchannel, where the rotor axis is perpendicular to the channel axis. When the cylinder rotates, a net force is transferred to the fluid due to the unequal shear stresses on the upper and lower surfaces of the rotor. Consequently, this causes the surrounding fluid in the channel to displace towards the microchannel outlet. The simplicity of the viscous micropump renders it ideal for micro pumping, however, previous studies have shown that its performance is still less than what is required for various applications. The performance of the viscous micropump, in terms of flow rate, pressure head and efficiency, may be enhanced by implementing more than one rotor into the configuration. The present study will numerically investigate the performance of various configurations of the viscous micropumps with multiple rotors, namely the dual-horizontal rotor, the triple-horizontal rotor, the symmetrical-dual-vertical rotor, and the 8-shaped dual-vertical rotor. The development of drag force with time, as well as the viscous resisting torque on the cylinders were studied. In addition, the corresponding drag and moment coefficients were calculated. Results show that the symmetrical-dual-vertical rotor configuration yields the best efficiency, and generates the highest flow rate. The steady state performance of the single-stage micropump was compared with the available experimental and numerical data, and was found to be in very good agreement. This work provides a foundation for future research on the subject of fluid phenomena in viscous micropumps.