Microfluidic patch integrated with cobalt oxide/cobalt phosphate nanozyme for electrochemical lactate sensing at neutral pH

: Non-invasive, real-time monitoring of lactate in sweat is critical for personalized health tracking and sports performance optimization. However, conventional enzyme-based lactate sensors suffer from limited stability and high cost, while many reported nanozyme systems exhibit optimal activity only under alkaline conditions, limiting their applicability in physiological environments. In this report, we develop a wearable integrated nanozyme-based electrochemical sensor for sweat lactate monitoring. The sensor comprises cobalt oxide (Co 3 O 4 ) and cobalt phosphate (Co 3 (PO 4 ) 2 ) nanoflakes on a screen-printed carbon electrode (SPCE), combined with a microfluidic unit for sweat collection and transport. Co 3 O 4 nanoflakes were electrodeposited and electrochemically activated to form a Co 3 O 4 /Co 3 (PO 4 ) 2 /SPCE platform for lactate detection. The structural morphologies, surface composition and chemical states, and crystalline information of the modified electrodes were analyzed using various analytical techniques, such as scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy. The Co 3 O 4 /Co 3 (PO 4 ) 2 /SPCE exhibited robust electrocatalytic activity for lactate detection at neutral pH, yielding a dynamic range of 1 - 80 mM with a sensitivity of 8.3 μA mM -1 cm -2 and a limit of detection of 0.3 mM. The developed sensor offers good selectivity against common electroactive sweat components (ascorbic acid, uric acid, and glucose). The microfluidic integrated sensor was tested dynamically with different concentrations of lactate, yielding a sensitivity of 5.2 μA mM -1 cm -2 . The device was validated by on-body sweat lactate monitoring during cycling, showing excellent accuracy (>91%) versus a colorimetric reference test. The integrated sensor enables real-time sweat lactate analysis for sports monitoring and personalized health tracking.