Abstract

Electroosmotic (EO) pumps can generate relatively high pressure and flow rate using no moving parts and small package volumes. Pumps with one micron (and smaller) pore diameters are promising for applications requiring high flow rate per power, such as drug delivery systems. We here show that such EO pumps exhibit significant concentration polarization (CP). CP occurs in electrokinetic devices when ionic current carried by electric double layers is significant compared to overall ionic current in the system. In the CP regime, EO pump models likely fail as these models do not account for the strong spatiotemporal variations in ionic strength. We present visualizations of CP in EO pumps, and confirm that enrichment and depletion propagation front dynamics correspond with CP theory. Additionally, we show that enrichment and depletion regions are generated at and propagate from electrodes of our system, and such regions appear to interact with CP effects.

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