Textile-Based Multistage Pressure-Tolerant Conformal Sensor for Unconstrained Human Physiological Signal Monitoring

Ballistocardiography (BCG)-based unconstrained monitoring techniques have garnered considerable research interest for long-term physiological signal monitoring owing to their exceptional wearability and adaptability across various scenarios. However, during measurement, nonnegligible human body weight can induce considerable deformation or even irreversible damage to the internal architecture of sensors, thereby imposing stringent requirements on structural design. Herein, a highly sensitive, pressure-tolerant, conformal, soft, and comfortable smart fabric is proposed for unconstrained BCG signal monitoring. Through nanoscale surface plasma modification, the smart fabric achieves multistage pressure sensing with high sensitivity (0.692 V kPa^-1 within a static pressure range of 1-9 kPa, corresponding to human body weight), a broad frequency response (0.5-10 Hz), and excellent mechanical stability (over 10,000 loading-unloading cycles under 7 kPa static pressure). The physiological signal monitoring system developed based on this sensor enables stable and accurate BCG signal acquisition, achieving up to 96% synchronization with electrocardiography signals, and can be seamlessly integrated into commercial mattresses for unconstrained physiological monitoring. Experimental results demonstrate the applicability of the system for daily life heart-rate assessment, highlighting its potential for unconstrained human health detection.