Flexible Wearable Microfluidic Colorimetric Sensor for Multiplex Bioenzyme-Free Detection of Creatinine, Urea, and Magnesium Ions in Sweat

Wearable microfluidic detection devices for noninvasive sweat analysis are highly desirable for human health monitoring. Herein, we present a bioenzyme-free microfluidic colorimetric detection device for simultaneous detection of creatinine (Cre), urea, and Mg²⁺ in sweat, enabling comprehensive kidney function and mental stress assessment. The device leverages a ternary catalytic system composed of H₂MoO₅ nanomaterial, Cu²⁺, and Cre, which exhibits significantly enhanced oxidase-like activity. This system directly catalyzes the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) to generate a blue product (ox-TMB), providing a robust platform for Cre detection without the need for bioenzymes. For urea and Mg²⁺ detection, 4-dimethylaminobenzaldehyde and chromium black T were employed as effective chromogenic reagents, respectively. A flexible multichannel microfluidic chip was fabricated, incorporating specific colorimetric reagent-modified paper chips into the corresponding reaction reservoirs. This design allows for the simultaneous detection of Cre, urea, and Mg²⁺ in sweat with linear ranges of 10-100 μM, 10-70 mM, and 0.5-8 mM, respectively. The device's performance was validated using actual sweat samples, with detection results analyzed via a smartphone application, demonstrating high accuracy and reliability. This work introduces a simple, low-cost, and stable bioenzyme-free microfluidic colorimetric detection device, offering significant potential for in situ and intelligent sweat analysis. The integration of smartphone technology further enhances its practicality, making it a promising tool for real-time health monitoring and point-of-care testing.