Abstract:

Objective To address the issues of high cost, insufficient stability, and cumbersome enzyme immobilization processes of traditional enzyme-based glucose sensors, and to meet the demand for flexible and high-sensitivity sweat glucose detection in wearable health monitoring, this study proposes a preparation strategy for an enzyme-free glucose sensor based on a flexible cotton yarn substrate.

Method First, cotton yarn was pretreated with a mixed solution of NaOH and Na₂CO₃ to improve surface reactivity. Then, a PEDOT conductive layer was constructed on the pretreated cotton yarn via low-temperature in-situ polymerization using EDOT as the monomer, Na₂S₂O₈ as the oxidant, and TsOH as the dopant. Subsequently, a three-electrode system was adopted for electrochemical deposition: the PEDOT composite cotton yarn composite served as the working electrode, a platinum column as the counter electrode, and a saturated calomel electrode as the reference electrode. A mixed solution of CuSO₄, Co(NO₃)₂·6H₂O, and citric acid (each 0.05 mol/L, pH adjusted to 11 with NaOH) was used as the electrolyte, and Cu₂CoO₃ nanoparticle arrays were deposited at -1.2 V to prepare Cu₂CoO₃/PEDOT composite cotton yarn composite fiber electrodes. The morphology, elemental distribution, and chemical valence state of the electrodes were characterized by SEM, EDS, and XPS, while their electrochemical and glucose-sensing performances were tested by an electrochemical workstation using CV and amperemetric I-t techniques.

Results SEM and characterizations showed that Cu₂CoO₃ nanoparticles with a cubic-spherical composite structure were uniformly load-ed on the PEDOT-modified cotton fiber surface, and Cu, Co, and O elements were distributed homogeneously. XPS analysis confirmed the successful composite of PEDOT and Cu₂CoO₃, with Cu existing as Cu²⁺, Co as Co²⁺ and Co³⁺, and abundant active oxygen species on the electrode surface electrochemical tests indicated that the electrode reaction was controlled by the diffusion step. At the optimal working potential of 0.70 V (vs. Hg/HgO), the electrode exhibited a linear glucose detection range of 0.005-12.7 mmol/L, with a high sensitivity of 1.173 mA/(mmol·cm²) in the low concentration range (0.005-2.2 mmol/L) and a detection limit of 1 μmol/L (S/N=3).

Conclusion The Cu₂CoO₃/PEDOT composite cotton yarn electrode composite fiber electrode prepared by the synergistic process of low-temperature polymerization and electrochemical deposition integrates the high conductivity of PEDOT and the synergistic catalytic activity of Cu₂CoO₃ bi-metallic oxide. It exhibits excellent performance including high sensitivity, low detection limit, rapid response, and good stability for glucose detection. With low-cost cotton yarn as the substrate and mild preparation conditions, this sensor provides a feasible technical route for the development of high-performance, non-invasive wearable health monitoring systems and has broad ap-plication prospects in sweat glucose detection.

Key words: cotton yarn, composite fiber electrode, conductive polymer, non-enzymatic glucose sensor, wearable sensing, biosensor, blood glucose monitoring