Entirely Self-Contained Electrochromic Epidermal Patch for Visualized and Multiplexed In Situ Sweat Analysis

Wearable sweat sensors demonstrate significant potential for monitoring sweat biomarkers that contain rich information pertinent to physiological state in a dynamic and noninvasive manner. However, these wearables typically and heavily rely on external wireless smart display terminals (e.g., smartphones and tablet PCs) to visualize monitoring outcomes, which may tremendously limit their convenience and practicality in certain but almost unavoidable scenarios (e.g., carrying and self-checking while running). Here, we present an entirely self-contained electrochromic epidermal patch (ESEEP) for the visualized, simultaneous, and calibrated analysis of multiple sweat metabolites and electrolyte biomarkers. ESEEP consists of a sweat transport module for skin-on sweat sampling and refreshing, a sweat sensing array module for simultaneous and multiplexed sweat analysis, a central control module for signal processing and full system automatic control, and a visualizing array module with a built-in electrochromic display for measurement data display. In volunteers, ESEEP enables simultaneous and real-time tracking of sweat glucose and Na⁺ for risk assessment of hypoglycemia and dehydration during physical exercise, which is readily and directly visualized within such wearables. ESEEP with distinctive design and functionality for self-visualized, multiplexed, and skin-on sweat monitoring enables a broad range of tailored physiological and diagnostic monitoring with conspicuously high practicality and convenience.