Microfluidic devices with channel cross sections measuring 4 × 10 µm2instrumented with gold microelectrodes were used to sense flow rates of ionicsolutions on the basis of electric impedance (EI) measured perpendicular to theflow. Negative pressures were applied to access ports of the microdevices togenerate flow of saline solutions (physiologic concentrations 0.9%) through themicro-EI recording zone with flow rates between 2.4 and 4.8 µl min−1.The EI spectra (100 Hz–20 MHz) recorded under flow conditions werecompared with the no-flow condition. Changes in the magnitudeof EI (at 350 Hz) for flow rates as low as 2.4 µl min−1were statistically significant compared with the no-flow condition. The observeddependence of EI on flow rate is attributed to the relative difference between therate of migration of charge-balancing electrolyte ions to the electrodesurface and the rate of removal of the same ions by forced convection. Anelectrochemical convection–diffusion model was used to study the observeddependence on flow. Simulations support the conceptual model that passingDC current from the gold electrodes into the ionic solution results in anincrease in ionic concentration near the electrode surface (due to the inwardmigration of counter-balancing ions). When the fluid flow rates increase,these counter-balancing ions are replaced by the bulk solution, therebylowering the average ionic concentration within the recording zone. This localconcentration drop results in an increase in the real part of the impedance.