Fabrication and characterization of electroosmotic micropumps

Electroosmotic flow (EOF) micropumps which use electroosmosis to transport liquids have been fabricated and used to achieve pressures in excess of 20 atm and flow rates of 3.6 μl/min for 2 kV applied potentials. These pumps use deionized water as working fluids in order to reduce the ion current of the pump during operation and increase thermodynamic efficiency. EOF pumps are fabricated by packing the 3.5 μm diameter non-porous silica particles into 500–700 μm diameter fused-silica capillaries and by using a silicate frit fabrication process to hold the particles in place. The devices have no moving parts and can operate as both open (high flow rate) and closed (high pressure) systems. Pressure versus flow rate performance data are presented and combined with measurements of physical dimensions, dry and wet weight, and ion current to calculate the pump structure porosity, tortuosity, effective pore radius, and zeta potential.