The membrane was synthesized as explained in the experimental section. Following the methodology for membrane synthesis outlined in the experimental section, we observed a thin chitosan membrane was synthesized between two electrodes following the introduction of the chitosan and NaOH solutions. Depending on flow conditions during their synthesis, membranes widths of less than 100 m (Figures ) and heights that were equal or less than that of the channel. CLSM was used to accurately characterize the sizes of two membranes formed in separate devices with different electrode spacing. In each case the membrane synthesis was stopped before the full vertical height of the channel was occupied. As observed previously the membrane grew downwards from the top of the device (PDMS side) which we believe is due to the membrane having a lower density than the pre-curses solutions. This resulted in a 5 m gap between the membrane and the bottom glass surface, whereas the membrane was well-connected to the PDMS/electrode side of the device as shown schematically in Figure . We exploited this small gap on the glass side of the device (opposite from the electrodes) to provide adequate connection between the anolyte and catholyte solutions for ion transport, in lieu of optimized transport properties through the membrane. In addition to reducing the internal resistance of the cell, we anticipated that this would provide a "controlled cross-over region" where differences in pressure could be alleviated without breaking the membrane. But, due to the gap position being opposite to the electrode layer, moderate amounts of cross-over could be tolerated without contamination of the liquid layer in contact with the electrodes. Before and after the chitosan membrane formation inside the microfluidic MFC, Nyquist plots were obtained from the EIS measurement with the microchannel filled with 100 mM phosphate buffer at QT=1 mL h -1 . To determine the resistance of the membrane and if its synthesis affected electrode performance, EIS was conducted. Solution/membrane resistance and charge transfer resistances (Rs/m, Rct, respectively) were quantitatively determined using an electrical equivalent circuit. To accomplish this, two different electrode configurations were selected: (i)