Development of a planar electrokinetic micropump
Electrokinetic (EK) micropumps use electroosmotic flow to produce high pressures in a compact design with no moving parts. An EK micropump has been fabricated on a 50 x 75 x 1.2 mm soda-lime glass substrate using standard microlithography and chemical wet etching techniques. The pump is 1 mm long in the flow direction and 0.9 μm x 38 mm in cross section. A preliminary model has been developed to characterize the flow rate, pressure capacity and thermodynamic efficiency of the pump. Experiments have been conducted using deionized (DI) water (pH = 5.6, conductivity = 1 x 10-3 S/m) as working fluid. Experimental data show a linear relationship between flow rate and counter pressure, which agrees well with the pump model. The data also show a nonlinear increase of flow rate with increasing applied voltage, which indicates temperate rise of the working fluid due to Joule heating. The flow rate of the pump at 1 kV degrades from 15 μl/min to 0.2 μl/min over a period of two months, while the pressure capacity remains around 0.3 atm and current of pump circuit remains around 2 μA. This long-term degradation, although still under investigation, is probably due to a collapse and bonding of the glass in the region of the thin (0.9 μm) pump channel.
