Wireless, battery-free wearable optoelectronic-colorimetric microfluidic sensor for multiplex sweat analysis

Wearable colorimetric biosensors enable noninvasive, real-time monitoring with intuitive readouts, yet most platforms rely on photographing the sensing area, making measurements highly susceptible to ambient light, background reflections, and user-dependent factors from camera angle, distance, and motion. Here, we present a fully integrated wireless, battery-free multi-modal optoelectronic-colorimetric microfluidic system that directly quantifies colorimetric signals in situ, eliminating the need for photography. The device combines a microfluidic patch containing colorimetric sensors for uric acid, alcohol, and pH with a detachable near-field communication (NFC) optoelectronic module comprising custom light-emitting diode (LED)-photodiode pairs for localized illumination and reflectance detection, enabling reading by both the NFC primary antenna and a smartphone. On-body studies in healthy participants and gout patients show robust interference-resistance performance across diverse ambient light levels and human skin tones, and reliable multiplex sweat analysis to track metabolic fluctuations following purine-rich and alcohol-rich diets and to evaluate allopurinol therapy.