Osmotic Pressure-Actuated Hydrogel Patch for Passive Sweat Extraction and Visual Sweat Glucose Monitoring at Rest

Wearable biosensors enable real-time, non-invasive detection of biomarkers in human sweat, providing valuable information for health monitoring, and are regarded as a research focus for next-generation personalized healthcare devices. However, several significant challenges remain, such as efficient sweat extraction and the inherent instability of natural enzymes. Herein, a visual hydrogel patch designed for sedentary populations (e.g., the elderly) that operates based on an osmotic pressure-driven passive sweat extraction strategy is designed for sweat glucose detection. The hydrogel patch co-encapsulates gold-platinum nanoparticles (AuPt NPs) with dual nanozyme activities (glucose oxidase mimic and peroxidase mimic) along with the chromogenic agent 3,3',5,5'-tetramethylbenzidine (TMB) within a polyvinyl alcohol (PVA) hydrogel matrix, using NaCl as an osmotic regulator. During detection, the patch is applied to the skin surface, where its hyperosmotic environment spontaneously draws sweat from sweat glands, enabling efficient passive sampling. The glucose is sequentially oxidized by the AuPt NPs, generating singlet oxygen radicals that oxidize TMB, resulting in a blue color change that allows visual quantification of glucose concentration. Quantitative analysis is further facilitated through RGB color profiling. This hydrogel patch offers a novel sweat collection and analysis strategy for sedentary individuals, contributing to supporting personalized health monitoring at home.