Hydrophobic Deep Eutectic Solvent‐Enhanced Filaments: A Green Breakthrough for Additive‐Manufactured Electrodes

Advancing sustainable materials for functional devices is a key challenge in green chemistry. This study reports, for the first time, the integration of a hydrophobic deep eutectic solvent (HDES) into a conductive filament composed of recycled polylactic acid (rPLA), carbon black, cellulose, and bio‐based castor oil, yielding a sustainable material with enhanced performance. The resulting composite not only incorporates renewable and recycled components but also exhibits enhanced mechanical and electrochemical performance. Cellulose enhanced the mechanical properties and printability of the filament, while HDES significantly improved its electrical conductivity, reducing bulk resistance from (1.16 ± 0.1) to (0.86 ± 0.02) kΩ representing an improvement over the previously reported CB/cellulose/rPLA electrode, and increased electrochemical performance. Electrochemical characterization of the fabricated electrodes demonstrated superior redox behavior, with enhanced charge‐transfer rates and electroactive surface areas compared to other bespoke filaments. The CB/cellulose/HDES/rPLA electrodes were successfully applied to the voltammetric determination of acetaminophen in water samples, achieving a linear concentration range of 5.0–300 µM and a limit of detection of 0.12 µM. These findings highlight the potential of HDES‐modified filaments in the development of novel, sustainable, high‐performance additive‐manufactured electrochemical sensors, combining additive manufacturing with green materials with enhanced functionality.