Conductive recycled PETg additive manufacturing filament for sterilisable electroanalytical healthcare sensors

Current reports of healthcare sensors within literature that use additive manufacturing electrochemistry all utilise conductive PLA, which is unsuitable for widespread use within the industry. Poly(ethylene terephthalate glycol (PETg) is a polymeric material with proven attributes for additive manufacturing due to its thermal and mechanical properties. Likewise, its excellent chemical stability transforms PETg into a desirable alternative for developing healthcare sensing devices. In this work, we report the production, physicochemical and electrochemical characterisations, as well as the electroanalytical performance of an enhanced electrically conductive additive manufacturing filament made with recycled poly(ethylene terephthalate glycol (rPETg) and a combination of carbon black, multi-walled carbon nanotubes and graphene nanoplatelets as conductive fillers. The post-print activation of additive manufactured electrodes from this material is optimised and shown to produce enhanced electrochemical performance compared to non-activated electrodes, with a k0 of 1.03×10−3 cm s−1. The sterilisation for the real application of sensors in the biomedical field is a critical point, the electrodes were submitted to standard UV light treatment showing to be reliable compared to PLA in the determination of uric acid (30–500 µM) and sodium nitrite (0.1–5 mM) within synthetic urine using differential pulse voltammetry and chronoamperometry techniques. A sensitivity and LOD for uric acid of 25.7 µA µM−1 and 0.27 µM, and 52.6 µA mM−1 and 2.69 µM for nitrite were obtained within synthetic urine, respectively. The re-useability of the electrodes was also tested for the detection of uric acid, showing that the electrode could be used up to 10 times before a significant decrease in the results was observed. We demonstrate that a new conductive rPETg with superior electrochemical performance has a prominent place within the development of additive manufactured-printed healthcare sensors due to its ability to be sterilised and re-used, low solution ingress, and its potential to tackle rising costs and plastic waste problems within the healthcare sector.