A simple electrochemical sweat sensor for glucose and ascorbic acid detection based on cu@ PHEMA hydrogel

Non-invasive, continuous monitoring of sweat biomarkers using flexible sensors enables real-time tracking of indicators such as glucose, electrolytes, and lactate, facilitating early disease detection and improved health management. In this paper, a flexible screen-printed electrode (labeled as Cu@PHEMA/SPE) based on a Cu 2+ doped poly(2-hydroxyethyl methacrylate) (PHEMA) hydrogel was prepared by a simple free radical polymerization method, which is used for glucose and ascorbic acid detection in sweat. This hydrogel exhibits excellent mechanical properties (184 kPa and 346 %), self-healing capabilities and recycled self-adhesive performance. Cyclic voltammetry (CV) and chronoamperometry techniques were employed to investigate the electrochemical properties of the hydrogel electrode in an alkaline solution and the flexible electrode in a neutral solution, with respect to glucose and ascorbic acid. The flexible electrode demonstrated a wide linear range, high sensitivity, and a low detection limit. Specifically, glucose detection ranged from 0 to 2 mM, exhibiting sensitivities of 122.24 and 24 μA/mM/cm 2 , with a detection limit of 4.5 μM. Moreover, it can detect ascorbic acid in the range of 0–220 μM, with sensitivities of 799.85 and 201.94 μA/mM/cm 2 , and a detection limit of 0.96 μM. Furthermore, the electrode displayed good selectivity for interfering substance such as uric acid (UA), dopamine (DA), lactic acid (LA), sodium chloride (NaCl), and potassium chloride (KCl), and it maintained performance despite external deformation. Notably, real sweat samples analysis demonstrated strong concordance with the results obtained using commercially available kits. These results indicate that this flexible electrode has great potential for application in wearable devices.