Overcoming Electron Transfer and Contact Resistance Limitations in 3D-printed Electrodes

The emergence of three-dimensional (3D) printing techniques has paved the way for the development of next-generation electrochemical sensors. The unique layer-by-layer process inherent to this technology offers the design freedom needed to create customized devices at a low cost with simple operation. However, despite efforts to enhance the electrochemical performance of 3D-printed sensors through surface treatments, they still fall short compared to conventional electrodes due to the poor conductivity of the filaments used in 3D printing. This study addresses two main challenges that limit the electrochemical performance of 3D-printed electrodes: the electron transfer rate at the electrode surface and the electrode’s electrical contact resistance. A photothermal gold reduction method was developed using an infrared laser, allowing for the direct formation of a gold film on the surface of the 3D-printed electrode. All process parameters were carefully optimized, resulting in a uniform coating and a fast, reproducible method to improve electron transfer at the electrode surface. Next, the impact of the electrical contact on the electrochemical response was explored. Experimental results, supported by finite element simulations, demonstrate that electrode design can have a large impact on contact resistance, leading to the design of an electrode configuration with low contact resistance. As a proof of concept, the final electrode was used for the electrochemical quantification of glucose over a linear range from 39 μmol L-1 to 15.2 mmol L-1, with a detection limit of 11 μmol L-1. This marks a significant advancement in the field of 3D-printed electrodes, enabling faster electron transfer through the gold film and reducing contact resistance, which lowers uncompensated resistance, a factor that has previously been overlooked in 3D-printed electrochemical devices.