Iontronic Textile‐based Capacitive Pressure Sensor for Unconstrained Respiration and Heartbeat Monitoring

Long‐term surveillance records of cardiac activity are essential for people at potential risk of cardiovascular disease. However, the existing mainstream technologies for cardiac monitoring, such as electrocardiography (ECG) and photoplethysmography (PPG), are inconvenient and prone to skin allergies due to contact measurements. Ballistocardiography (BCG) is a vibration signal related to cardiac activity, which can be monitored in an unconstrained way. Herein, an iontronic textile‐type flexible capacitive pressure sensor (i‐TFCPS) based on ionic liquid doped hollow‐porous fiber is developed to monitor physiological signals. With a high sensitivity of 7.26 kPa −1 , a wide pressure range (10 Pa–600 kPa), a fast response time of 30 ms, and decent durability over 3500 cycles, the i‐TFCPS is simultaneously capable of detecting and tracking the static and dynamic changes of sitting posture, and subtle physiological information, such as respiration and BCG signals. Benefits from the iontronic textile as sensitive dielectric, the capacitive pressure sensor is able to monitor the subtle BCG signal under high static pressure in an unconstrained state, showing great potential for unobtrusive cardiac monitoring in home, office and hospital.