3D-Printed Electrodes Based on Polylactic Acid and Carbonaceous Materials for Electrochemical Sensors and Biosensors: Fabrication and Surface Activation via Chemical, Electrochemical, and Laser/Plasma Methods

Abstract

Surface preparation of 3D-printed electrodes fabricated from conductive filaments is essential for enhancing their electroanalytical performance, as the inherent presence of insulating polymer matrices limits electrical conductivity. To overcome this limitation, a variety of post-treatment strategies have been investigated, including chemical and electrochemical approaches, which have demonstrated promising results. In contrast, biological methods, such as enzymatic treatments, are often time-consuming, and reagent-free techniques may suffer from reproducibility issues, when not automated, due to operator-dependent variability. Among the reagentless methods, laser and plasma treatments have emerged as reliable strategies to expose the conductive material, offering an environmentally friendly route for surface activation. This review explores 3D printing technologies, commonly used filaments, and the diverse activation protocols reported for electrodes based on polylactic acid and carbon-based materials, including chemical, electrochemical, laser/plasma methods and their combinations. A critical analysis of these activation techniques and others found in the literature is also presented, highlighting their advantages, limitations, and applicability. Despite significant progress, no consensus has been reached regarding optimal treatment conditions, and the lack of standardized protocols remains a challenge. Furthermore, many studies select activation strategies based solely on electrochemical performance metrics, often without statistical validation, which may lead to the adoption of unnecessarily resource-intensive procedures. Surface treatment methods should be chosen carefully, considering reagent availability, health and environmental risks, and economic feasibility. Optimizing surface activation protocols is essential to ensure improved electrode performance and reliability. Continued research is needed to refine these methods and establish standardized methodologies, ultimately advancing the development and application of 3D-printed electrodes in electrochemical sensing and biosensing.