Non-toxic flexible screen-printed MWCNT-based electrodes for non-invasive biomedical applications

Here, a non-toxic, flexible, low-cost, and disposable multiwalled carbon nanotube (MWCNT)-based screen-printed electrode (SPE) was developed for non-invasive health monitoring applications. A novel MWCNT-based conductive paste formulation was prepared and optimized for printing SPEs using a computer numerical control (CNC)-made stencil. The electrodes were electrochemically characterized and subjected to physical stress to investigate their mechanical durability in extreme situations such as heavy exercise. The reproducibility of the fabrication approach and the stability of the electrodes were also demonstrated. The electrochemical performance of the electrodes was tested with first dopamine (DA) and then glucose. The SPE displayed a linear response in the DA concentration range of 5-500 μM with a limit-of-detection (LOD) of 0.87 μM. Detection of glucose was carried out based on electrochemical-enzymatic redox cycling in artificial sweat; wherein the flexible SPE-based biosensor exhibited a linear response, particularly up to 1 mM with an LOD of 31.7 μM. It is likely that the high sensitivity was achieved due to the large surface-to-volume ratio of MWCNTs and micro/nanoporous network morphology of the electrode surface which was observed in scanning electron microscopy (SEM). Cytotoxicity tests confirmed that the flexible MWCNT-SPEs are non-toxic and therefore safe for non-invasive health monitoring. As a result, the electrodes displayed excellent electrochemical behavior and are expected to contribute to wearable sensor technology due to features such as high stability, sensitivity, flexibility, and non-toxicity.