Effects of Resistance Compensation on Laser-Induced Graphene Electrodes

Laser-induced graphene (LIG) offers a promising approach for fabricating low-cost, flexible, and disposable electrochemical sensors. However, the electrical resistance associated with thin conductive tracks and their connections can introduce substantial ohmic potential losses, compromising potential control and distorting electrochemical measurements. Here, we report a paper-based LIG electrochemical platform incorporating a four-terminal configuration designed to minimize resistance-related distortions through separate current-carrying and potential-sensing pathways. The electrodes were fabricated by direct CO2 laser scribing of Kraft paper, producing a porous, graphene-like carbon network characterized by scanning electron microscopy and Raman spectroscopy. The electrochemical effects of resistance compensation were systematically investigated using cyclic voltammetry and electrochemical impedance spectroscopy with ferricyanide/ferrocyanide, hexaammineruthenium, dopamine, and paracetamol. Resistance compensation substantially improved voltammetric peak definition and potential control, shifting the dopamine oxidation peak from 0.70 to 0.40 V and reducing the fitted uncompensated series resistance from 197 to 35 Ω for hexaammineruthenium. In contrast, the charge-transfer resistance remained nearly unchanged, indicating that the observed improvements primarily resulted from reduced ohmic distortions rather than changes in intrinsic electron-transfer kinetics. Under resistance-compensated conditions, the LIG electrodes enabled dopamine determination over 120–900 μmol L–1, with a detection limit of 29 μmol L–1, and paracetamol determination over 125–1660 μmol L–1, with a detection limit of 37 μmol L–1, using cyclic voltammetry. Differential pulse voltammetry further improved paracetamol detection, achieving a detection limit of 2.5 μmol L–1 over a linear range of 10–60 μmol L–1. The proposed platform was successfully applied to paracetamol determination in commercial pharmaceutical tablets, providing a recovery of 93%, in close agreement with the 94% obtained by high-performance liquid chromatography. The integration of laser-based fabrication and resistance compensation provides a practical strategy for minimizing measurement artifacts and improving the reliability of low-cost, paper-based electrochemical sensors.