A novel electro-osmotic pump design for nonconducting liquids: theoretical analysis of flow rate-pressure characteristics and stability

We present the design and theoretical analysis of a novel electro-osmotic (EO) pump for pumping nonconducting liquids. Such liquids cannot be pumped by conventional EO pumps. The novel type of pump, which we term the two-liquid viscous EO pump, is designed to use a thin layer of conducting pumping liquid driven by electro-osmosis to drag a nonconducting working liquid by viscous forces. Based on computational fluid dynamics, our analysis predicts a characteristic flow rate of the order nL/s/V and a pressure capability of the pump in the hPa/V range depending on, of course, achievable geometries and surface chemistry. The stability of the pump is analyzed in terms of the three instability mechanisms that result from shear-flow effects, electrohydrodynamic interactions and capillary effects. Our linear stability analysis shows that the interface is stabilized by the applied electric field and by the small dimensions of the micropump.