Dual-mode sensing of pulse and sweat electrolytes via integrated hydrogel-based biosensors for health management

With the rapid development of wearable health monitoring technology, real-time, non-invasive, and multi-modal physiological signal acquisition has become a key requirement for improving disease warning and health management levels. Here, we demonstrate a dual-mode wearable health monitoring system based on functionalized hydrogel, which realizes accurate detection of ionic concentrations in human sweat and stable extraction of pulse wave signals. A porous hydrogel sweat sensing platform based on polyvinyl alcohol (PVA) is designed to solve the problems of low electrolyte penetration efficiency and skin irritation during sweat detection. Combined with electrodes modified with polypyrrole (Ppy) and ionophores, electrochemical sensors capable of measuring the concentrations of sodium (Na⁺) and chloride (Cl^-) ions are constructed. The sensitivity of the sensors is close to theoretical value of the Nernst equation, exhibiting good selectivity, repeatability, long-term stability, and reliability. In order to capture weak pulse signals, we have developed a highly sensitive pulse sensor based on PVA/poly (ethylene glycol) (PVA/PEG) dual network conductive hydrogel. Furthermore, a pyramid array structure is designed to develop piezoresistive flexible pressure sensor. This sensor features high sensitivity, rapid response/recovery time (25.0 ms/17.5 ms), low detection limit (7.9 Pa), and long-term stability, capable of accurately detecting arterial pulse waves and heart rate under various physiological conditions. A matching smartphone-integrated monitoring system is then developed, which supports dual channel ion detection, pulse waveform analysis and wireless data transmission. This study provides an effective solution for personalized health monitoring, and shows the application potential of functional hydrogel in the field of wearable health monitoring.