An Ultrastable Wearable Electrochemical Sensor for Prolonged Monitoring of Electrolyte Loss and Hydration

Maintaining proper hydration and electrolyte balance is essential for optimal health and performance, as imbalances can lead to serious health risks. Wearable technology has become a key tool for monitoring these critical parameters, offering real-time insights that are particularly valuable for active individuals and those with medical conditions. However, the effectiveness of wearable sensors during dynamic physical activities is often limited as their durability and stability can be compromised. Herein, we present an ultrastable and durable ready-to-use sweat electrolytes and secretion reporting system (r-SENSER) for continuous tracking of sweat electrolytes (i.e., Na⁺ and K⁺) and secretion rate. The electrolyte sensor features internal calibration and enhanced interfacial stability through a semisolid electrolyte and a hydrophobic ion-to-electron transducer. The electrolyte sensors exhibited exceptional stability and eliminated the need for manual calibration, making it user-friendly and significantly extending their operational lifespan with a shelf life of over one month. Additionally, the sweat rate sensor, designed with a droplet-based sweat dispensing system, ensures accurate and prolonged sweat rate monitoring during strenuous activities. We validated the r-SENSER in individuals engaged in various indoor and outdoor activities for loss of electrolytes and hydration analysis. We envision that r-SENSER could play a transformational role in sports monitoring and health management, enabling proactive and informed decision-making without the need for professional oversight.