Handling electric connections in 3D-printed electrodes and sensors

Voltammetric and amperometric sensors typically consist of an electroactive surface, an electrode substrate, and connection tracks. While metal connectors exhibit negligible resistance, semiconductor materials, conductive polymers, or composites can introduce significant electrical resistance. This study investigates the electrical behavior of 3D-printed conductive polymer tracks and metal connections, focusing on limitations and improvements. Carbon black PLA (CB-PLA) was chosen for its favorable electrical properties. Printed tracks showed higher resistivity (17 Ω·cm) than the raw filament (6 Ω·cm). The electrical contact resistance (ECR) between nickel-plated metals and CB-PLA ranged from 10² to 10³ Ω. Pressed contacts (e.g., alligator clips) were unstable and introduced noise, while a welded metal-polymer contact (WMPC), achieved via induction heating, improved stability. Despite high resistivity, the electrochemical behavior remained unaffected, apart from an Ohmic drop requiring compensation for accurate sensor performance. To address this, a four-electrode potentiostat was proposed for dynamic Ohmic drop compensation. Cyclic voltammetry experiments were performed using a custom 3D-printed electrode with dual conducting tracks to independently monitor potential and current. Results from a commercial four-electrode potentiostat were compared with those from a conventional three-electrode system. A four-electrode potentiostatic module (FEPM) was developed for compatibility with standard three-electrode instruments, yielding comparable results. Peak current varied linearly with hexaammineruthenium(III) concentration (R² = 0.992) and with the square root of the scan rate (R² ≥ 0.993). Differential pulse voltammetry confirmed enhanced performance with the four-electrode setup. These findings highlight key considerations for integrating 3D-printed components into electrochemical systems and mitigating ECR and Ohmic drop.