High pressure electroosmotic pump based on a packed bed planar microchip

A high pressure electroosmotic flow (EOF) pump was fabricated within a glass substrate and tested to characterize its fluid dynamic performance. The EOF pump was constructed on a compact, planar microchip platform with (L × W × D) dimensions of 10 cm × 3.6 cm × 0.3 cm. The pumping region itself consisted of a straight channel (3 cm × 160 μm × 62 μm) uniformly packed with 3.38 μm silica microspheres held in place by a microfabricated weir structure. Characterization of the microchip EOF pump included pressure and flow rate measurements as a function of voltage and system backpressure for a buffered aqueous fluid containing 10 mM cyclohexylamino alkyl sulfonate CHES. Measurements indicate a maximum pressure of 25 atm and a maximum measured flow rate of 85 nL/min. Linear relationships of pressure and flow rate with voltage were confirmed. Current measurements show linear profiles with voltage for flow rate and maximum pressure measurements, indicating minimal effects due to Joule heating under either test condition. Design and performance considerations relating to fluid dynamic considerations are discussed. The large pressures generated electrokinetically by the microchip EOF pump show the potential for a compact motive source that allows for easy integration with applications requiring high pressures.