Handling electric connections in 3D-printed electrodes and sensors. Part II. Instrumentation

This study explores the integration of 3D-printed electrodes made from carbon black-poly(lactic acid) (CB-PLA) into electrochemical sensors, focusing on the challenges posed by the polymer/metal electrical contact resistance (ECR) and Ohmic drop. We demonstrate that while CB-PLA electrodes offer promising potential for sensor applications, the ECR and intrinsic resistance of printed tracks can significantly affect the performance. We propose the use of a four-electrode potentiostat, which allows for dynamic compensation of Ohmic drop, thereby enhancing the reliability of measurements. We conducted cyclic voltammetry experiments using a custom-built 3D-printed electrode with dual conducting tracks to independently monitor potential and current. The results obtained with a commercial four-electrode potentiostat were compared to those from a conventional three-electrode potentiostat. To enable users without a four-electrode potentiostat to use the described electrode, a four-electrode potentiostatic module (FEPM) was developed. The results from combining a three-electrode instrument with the FEPM are comparable to those from a commercial four-electrode instrument. Quantitative analysis revealed that the peak current varied linearly with analyte concentration (R² = 0.992) and with the square root of the scan rate, showing high correlation coefficients for both cathodic (R² = 0.993) and anodic (R² = 0.999) peak currents. Differential pulse voltammetry experiments further confirmed the improved performance of the four-electrode setup, with comparable results obtained using the three-electrode potentiostat and FEPM combination. These findings underscore the importance of careful instrumentation design when integrating 3D-printed components into electrochemical systems, and suggest practical approaches for mitigating ECR and Ohmic drop in such applications.