Preprinting Saponification of Carbon Thermoplastic Filaments Provides Ready-to-Use Electrochemical Sensors

Carbon-based electrodes have been impactful in a wide array of applications; however, the balance between electrochemical performance and ease of fabrication is still a major challenge. Three-dimensional (3D) printing has emerged as a promising solution to provide high-throughput easy production of precise carbon-based electrochemical sensors, but the printed electrodes from commercial filaments can exhibit poor or no electrochemical performance. Varying strategies have been utilized to overcome these challenges with different levels of success. Our study focuses on the systematic use of saponification using hydroxide to selectively remove polylactic acid (PLA) from the commercially available carbon thermoplastic filament preprinting. Cyclic voltammetry of varying redox probes was used to access the difference between multiwalled carbon nanotube (MWCNT)/PLA and carbon black (CB)/PLA electrodes made with native and modified filament. Resistivity was reduced following saponification of filaments over increasing time, where surface changes were observed in the MWCNT/PLA filaments. CB/PLA and MWCNT/PLA electrodes made by using modified filaments had greater current responses and faster electron transfer kinetics than electrodes made with the native filament. Modified filament-made CB/PLA electrodes also exhibited greater electrochemical performance when compared to electrochemically treated CB/PLA electrodes made with the native filament. The preprinting saponification of the carbon PLA filament reported here provides a novel approach for fabricating high-performance ready-to-use 3D printed electrochemical sensors with utility in applications ranging in sensing and energy storage.