Wearable Perspiration Characteristic Sensor Using Bi-Directional Driver Circuit

The number of patients with heat stroke has been increasing, and it is one of the social problems. Heat stroke frequently occurs indoors and often goes unnoticed, particularly at home. Therefore, our goal is to prevent heat stroke by developing a wearable sensor that can measure the volume and salinity of perspiration. In the proposed sensor, textile-based electrodes with conductive adhesive are applied to the fiber material. Because perspiration lowers the impedance between the textile-based electrodes, perspiration can be estimated from the impedance change. However, both the volume and salinity of perspiration contribute to these impedance changes, making it challenging to distinguish between these effects. To address this challenge, we utilized the impedance characteristics of water and salinity. A bidirectional driver circuit for impedance estimation was proposed and implemented. The measurement results indicate that the proposed method can measure the volume and salinity of perspiration from the impedance changes in the electrode.