The Wearable and Flexible Biosensors for Sweat Glucose Detection using Paper-based Interdigital Electrodes Modified by PEDOT:S-H and Cellulose Nanofiber Nanocomposites

Flexible PEDOT:S-H/CNF paper biosensor enables noninvasive sweat glucose monitoring for wearable use. • 0.2:0.6 EDOT:S-Na₂S₂O₈ ratio yielded 17.08   S/cm conductivity, low swelling, and superior performance. • 3.ENS strategy enabled stable GOx covalent binding, enhancing activity and ensuring long-term stability. • 4.Optimized IDE geometry enhanced charge transfer, boosting sensitivity and lowering resistance. • 5.<5% glucose error in sweat across varied conditions enables real-time clinical monitoring. Biosensors enable disease, environmental, and metabolite monitoring due to high sensitivity, rapid response, and biocompatibility. However, wearable formats suffer from limited flexibility, inefficient enzyme immobilization, and poor wearability. Here, we present a wearable, stable, fast-responding sweat glucose (SG) biosensor using paper-based interdigitated electrodes (PIDE) coated with PEDOT:S-H/cellulose nanofiber (PSH/CNF,PCN) and covalently immobilized glucose oxidase (GOD). The composite exhibits high conductivity (17.08   S/cm), low swelling, and robustness; PSH is synthesized from EDOT:S and Na₂S₂O₈ (0.2:0.6) and mixed with CNF at 1:16 (v/v). The optimized PIDE geometry (1   mm spacing, 0.5   mm width, 10   mm length, 6 pairs) reduces interfacial impedance (180 Ω) and improves sensitivity (0.042   mA/mM). A one-sided GOD immobilization via 1-ethyl-(3-dimethylaminopropyl) carbodiimide hydrochloride/N-hydroxysuccinimide/succinic acid (EDC/NHS/SA, ENS) coupling yields ~2% enzyme leaching. The sensor shows a fast response (1.172   s) and peak current (0.1154   mA). Robust performance persists across pH 4–10, 36–39 °C, 3–5   mg/mL NaCl, and 30–70% RH. An SG concentration–impedance model (0.064–4.102   mmol/L) is established. Predicted SG trends deviate by <5% from blood glucose across five physiological states. The PIDE design enables better flexibility, integration and stability than conventional three-electrode sensors. This PIDE biosensor enables sensitive, stable noninvasive SG monitoring. Download: Download high-res image (167KB) Download: Download full-size image