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We have previously demonstrated that polymer plugs with sub-micron pores can suppress unwanted pressure-driven flow and enhance electro-osmotic flow in a microchannel. This paper presents two separate concepts related to electrode placement and biasing strategy that further abate generation of bubbles in the main flow. In the first concept the drive signal is applied to a main EOF porous plug through high flow resistance porous bridges present outside the main flow. In the second approach, metal electrodes are located within the main channel across a series of dielectrically isolated narrow channels. Bubble generation is suppressed with a high-frequency square wave drive, and net unidirectional flow is achieved by modulation of the zeta potential on the narrow channel surfaces. Flow velocities of 10-66 μm/sec in 20-μm high channels have been achieved by these two methods.