This study compares fluid velocity magnitude and direction for three different glassy carbon (GC) electrode systems effecting alternating current (AC) electroosmotic pumping. The flow behavior is analyzed for electroosmotic pumping performed with asymmetric coplanar electrodes. Subsequently, effects of adding microposts array of two different heights (40 μm and 80 μm) are studied. Experimental results demonstrate that as peak-to-peak voltage is increased above 10 V peak-to-peak, the flow reversal is achieved for planar electrodes. Utilization of microposts-enhanced asymmetric electrodes blocks the flow reversal and alters the magnitude of the fluid velocity at the application of larger voltages (above 10 V peak-to-peak). Understanding of the consequences of three-dimensional geometry of asymmetric electrodes would allow designing the electrode system for AC electroosmotic pumping and mixing, as well as bidirectional fluid driving with equal forward and backward flow velocities.

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