Bio-based plasticizer Babassu oil for custom-made conductive additive-manufacturing filaments: towards 3D-printed electrodes applied to cocaine detection.

Babassu (Atallea sp.), a native palm tree from South America's Amazon produces bio-oil and biochar with significant potential for industrial applications. Babassu oil as a bio-based plasticizer is reported here for the first time to replace petrochemical alternatives in the production of conductive filaments for additive manufacturing purposes. The newly developed filament, consisting of 30 wt.% carbon black (CB), 60 wt.% polylactic acid (PLA), and 10 wt.% Babassu oil, demonstrates enhanced thermal stability, improved printability, and superior electrochemical performance. 3D-printed electrodes made from this Babassu-CB/PLA filament outperform those made from commercial CB/PLA filaments, exhibiting better voltammetric responses (e.g., lower peak-to-peak separation and higher current intensity) for inner-sphere redox probes. As a proof-of-concept, these bio-based electrodes were successfully used to detect cocaine in real-world street samples, with a limit of detection (LOD) of 1.2 µmol L. The Babassu-CB/PLA electrodes provided reliable cocaine quantification without interference from common adulterants such as caffeine, paracetamol, and phenacetin and showed no matrix effects, as confirmed by recovery values ranging from 88 to 102%. Notably, the use of Babassu oil eliminates the need for laborious post-treatment protocols to achieve optimal electrochemical performance. In this study, only mechanical polishing on the electrode surface is required. This study highlights the potential of Babassu oil as a sustainable alternative in the fabrication of conductive filaments for electrochemical applications, advancing the field of environmentally friendly and efficient 3D-printed sensors.