Optimised graphite/carbon black loading of recycled PLA for the production of low-cost conductive filament and its application to the detection of β-estradiol in environmental samples

• Published in: Mikrochimica acta (1966) 2024-07, Vol.191 (7), p.375, Article 375
• Main Authors: Augusto, Karen K. L., Crapnell, Robert D., Bernalte, Elena, Zighed, Sabri, Ehamparanathan, Anbuchselvan, Pimlott, Jessica L., Andrews, Hayley G., Whittingham, Matthew J., Rowley-Neale, Samuel J., Fatibello-Filho, Orlando, Banks, Craig E.
• Format: Article
• Language: English
• Subjects: Additive manufacturing; Analytical Chemistry; Bioplastics; Carbon black; Castor oil; Characterization and Evaluation of Materials; Chemistry; Chemistry and Materials Science; Electrochemical analysis; Electrodes; Electrolytic analysis; Graphite; Low cost; Low temperature; Manufacturing; Microengineering; Nanochemistry; Nanotechnology; Original Paper; Polylactic acid; Recycled materials; Sex hormones; Water sampling
• ISSN: 0026-3672; 1436-5073; 1436-5073
• DOI: 10.1007/s00604-024-06445-7

The production, optimisation, physicochemical, and electroanalytical characterisation of a low-cost electrically conductive additive manufacturing filament made with recycled poly(lactic acid) (rPLA), castor oil, carbon black, and graphite (CB-G/PLA) is reported. Through optimising the carbon black and graphite loading, the best ratio for conductivity, low material cost, and printability was found to be 60% carbon black to 40% graphite. The maximum composition within the rPLA with 10 wt% castor oil was found to be an overall nanocarbon loading of 35 wt% which produced a price of less than £0.01 per electrode whilst still offering excellent low-temperature flexibility and reproducible printing. The additive manufactured electrodes produced from this filament offered excellent electrochemical performance, with a heterogeneous electron (charge) transfer rate constant, k 0 calculated to be (2.6 ± 0.1) × 10 −3 cm s −1  compared to (0.46 ± 0.03) × 10 −3 cm s −1 for the commercial PLA benchmark. The additive manufactured electrodes were applied to the determination of β -estradiol, achieving a sensitivity of 400 nA µM −1 , a limit of quantification of 70 nM, and a limit of detection of 21 nM, which compared excellently to other reports in the literature. The system was then applied to the detection of  ß -estradiol within four real water samples, including tap, bottled, river, and lake water, where recoveries between 95 and 109% were obtained. Due to the ability to create high-performance filament at a low material cost (£0.06 per gram) and through the use of more sustainable materials such as recycled polymers, bio-based plasticisers, and naturally occurring graphite, additive manufacturing will have a permanent place within the electroanalysis arsenal in the future. Graphical abstract