Wireless light-gated photoelectrochemical microneedle wearables for zero-bias longitudinal monitoring in interstitial fluid.

Wearable chemical sensors could enable continuous health monitoring, but long-term measurements in interstitial fluid are limited by power consumption, electrochemical interference and signal drift during wear. Here we show a light-gated photoelectrochemical microneedle wearable for zero-bias chemical monitoring in subcutaneous interstitial fluid. The device combines a swelling-tolerant conductive hydrogel microneedle array, a plasmon-enhanced photoelectrode and a miniaturized module for light excitation, current recording and Bluetooth transmission. Visible light drives oxygen-mediated redox chemistry without an applied bias, reducing interfering electrochemical reactions and power demand. Using uric acid as a representative analyte, the wearable provides wireless readout under hydration and mechanical deformation. In vivo disease-model validation was performed in male rats and mice, where the device tracked uric acid dynamics in chronic kidney disease, diabetic hyperuricemia and bacterial treatment, with trends correlating with blood measurements. This light-gated microneedle architecture offers a modular route for longitudinal monitoring of interstitial-fluid chemistry.