## 3 Results  
Since the resistance of interconnection tracks contribute to the performance of circuits fabricated with different manufacturing methods, a comparison of PCB copper tracks and inkjet-printed silver tracks is requisite. The resistivity and conductive layer thickness will not be same for the two types of tracks, indicating sheet resistance as a logical figure of merit. Nevertheless, in this work the conductive network artwork is the same for the two circuits, rendering the resistance of tracks with the same planar dimensions a more reasonable basis of comparison. Figure 4 shows the experimental results of a PCB copper track and a conductive silver track printed on a paper substrate, both with a width of 300 \(\upmu\)m and a length of 8 mm. Figure 4 indicates that both the PCB and printed track have a linear region over the full 2 V voltage range of the impedance analyzer, which is adequate for the potentiostat application under consideration here. The discontinuity around the 1 V input voltage is attributable to voltage range switching in the measurement instrument, but was not corrected for in the linear regression for the extraction of resistance values. The resistance of the printed silver track is approximately 160% of the resistance of the copper PCB track. As an interesting aside, the results of Figure 4 indicate significantly better contact resistance on the printed silver track than on the copper PCB track. Although not confirmed yet, it is conjectured that the round-tip measurement pogo pins indent the more pliable silver to provide a larger contact surface. The electrochemical performance of the potentiostats on paper and PCB, and also the development board potentiostat, is validated and compared to that of the Autolab in Figure 5, by performing three sets of cyclic voltammetry tests at a 50 mVs\({}^{-1}\) scan rate for each sensing system, on three identical Dropsens electrodes using a 0.1 M KCL solution containing 5 mM [Fe(CN)6]\({}^{3-/4-}\). The curve of the Autolab indicates a reversible system due to the similar absolute values obtained for redox and oxidation currents [34]. Table 2 investigates the result further by comparing the average and standard deviation of the current peak heights for each set of experiments. The cyclic voltammetry contour of the redox and oxidation currents of the four systems are similar and the standard deviation of each system is less than 10%, indicating that even though the development board, PCB potentiostat and paper-based potentiostat may require further optimization, each of the systems shows repeatability across the experiments performed. Figure 4: Current-voltage transfer curves for a PCB track and a silver inkjet-printed track on paper of equal planar dimensions. In Figure 5, the paper-based potentiostat, PCB potentiostat and development board produce more signal noise than produced by the Autolab. The vertical discontinuity in data that occurs when the input potential is zero for the paper-based potentiostat, PCB potentiostat and development board is due to noise generated by the change in sign of the LMP91000 chip registers. The paper-based potentiostat produces similar results to the other potentiostats, but exhibits a smaller amplitude current signal due to the higher circuit resistance. The current amplitude ratio between the paper-based and PCB potentiostats correlates well with the resistance ratio results presented in Figure 4. Voltage drops across the network tracks cause a potential difference between the sensor electrodes and the potentiostat chip, which will cause an apparent shift in the oxidation and reduction peak potentials. Particularly if these potential differences are in the same order of magnitude as the solution ohmic drops, the peak potentials will be inaccurate. The change in experimental conditions indicates that for the paper-based potentiostat, the given scan rate may no longer be optimum. Future work will address these issues and further improve the performance of the paper-based potentiostat.