Thread‐Based Wristwatch Sensing Device for Noninvasive and Simultaneous Detection of Glucose and Lactate

Abstract An electrochemical sensing device based on a cotton‐thread electrode for real‐time and simultaneous detection of sweat glucose and sweat lactate is reported. The cotton thread surfaces are simply modified by cellulose nanofibers/carbon nanotube ink‐Prussian blue/chitosan to enhance liquid adsorption, bioreceptor immobilization, and sensor performance in addition to minimize potential irritation and allergies on the wearer's skin. The modified thread surfaces are characterized by laser scanning confocal microscopy, scanning electron microscopy, and Fourier transform Raman spectroscopy. Amperometry is carried out via hydrogen peroxide detection for electrochemical characterization of the modified thread electrodes. A circuit and digital readout of this wearable sensor are customized designed to be integrated with thread electrodes for real‐time and simultaneous detection of sweat glucose and sweat lactate. The wristwatch sensing device provides a linear range of 0.025–3 × 10⁻³ m with a detection limit of 0.025 × 10⁻³ m for glucose and a linear range of 0.25–35 × 10⁻³ m with a detection limit of 0.25 × 10⁻³ m for lactate. This device can effectively determine the cut‐off levels of both glucose and lactate, which can distinguish between a normal individual and one with a diabetic condition. This platform opens a new avenue for noninvasive and real‐time detection of other sweat biomarkers.