A programmable planar electroosmotic micropump for lab-on-a-chip applications

Abstract

A programmable planar micropump for lab-on-a-chip applications has been developed. The device consists of an electroosmotic micropump combined with a mass flow sensor in a closed control loop. The micropump design with a vertical arrangement of multiple narrow polymer pumping microchannels reduces the pump area to 1/10 compared to planar micropumps with widened shallow pumping channels. This design allows the fabrication of the channel system in only one process step and is compatible with post-CMOS processing. An analytical model is presented to estimate the flow rate in a field-free pressure-driven section of the channel. It is shown that the micropump with optimized dimensions of rib structures allows high pressure low voltage pumping. The electroosmotic micropump with a suggested design using microchannels of SU-8 and polyacrylamide gel electrodes has been fabricated and tested. The pumping rate is bidirectionally linear and reaches 10 nl min−1 in a 1 cm long pressure-driven channel at an applied voltage of 40 V, which corresponds to a zero-flow pressure of 65 Pa. The micropump has been operated successfully in a closed control loop together with an on-chip mass flow sensor and external control circuitry for flow rates between 0 and 30 nl min−1.