A planar electroosmotic micropump

Electroosmotic (EO) micropumps use field-induced ion drag to drive liquids and achieve high pressures in a compact design with no moving parts. An analytical model applicable to planar, etched-structure micropumps has been developed. This model consists of pressure and flow relations in addition to an analytical expression that can be used to estimate the thermodynamic efficiency of planar EO pumps. The analytical model was applied to guide the design of a pump consisting of an etched EO flow chamber for near-optimal hydraulic power performance. To achieve high efficiency, the working fluid used was deionized (DI) water with a conductivity of 3.0 x 10(-4) S/m (pH = 5.7). The EO micropump was fabricated on a soda-lime glass substrate using standard microlithography and chemical wet etching techniques. The active pumping volume of the device consists of a wet-etched flow channel 1-mm long in the flow direction and 0.9 mum by 38-mm in cross section. The pump performance agrees well with the theoretical model. The pump can produce a maximum pressure of 0.33 atm and a maximum flow rate of 15 muL/min min at 1 kV.