A Flexible Triboelectric-Based Sensor for Seismocardiography Monitoring.

Seismocardiography (SCG) is a promising noninvasive modality for cardiovascular monitoring. By capturing subtle chest wall vibrations induced by the mechanical pumping activity of the heart at the body surface, SCG is of considerable value for blood pressure-related cardiovascular risk assessment and cardiac function monitoring. However, continuous SCG monitoring in daily life settings still relies predominantly on rigid accelerometers, and reports on flexible acquisition systems remain scarce. This is mainly because SCG signals are characterized by low frequency, low amplitude, and high sensitivity to the sensor-skin interface, requiring the sensor to achieve stable, high-fidelity acquisition of weak chest wall mechanical vibrations while maintaining conformal contact and wearing comfort. To address this challenge, this study proposes a flexible pressure sensor based on the triboelectric effect. The sensor adopts a single-electrode contact-separation structure and is composed of a polymer material capable of achieving a high negative charge density and a nickel foil electrode. The sensor exhibits a sensitivity of 3.76 V/N within a small force range of 0-200 mN, shows good frequency response over the 0.5-25 Hz band, and maintains stable output after approximately 5300 cycles. The sensor was attached to the lower-middle segment of the sternum to capture weak vibration signals generated by cardiac mechanical activity and transmitted through the chest wall, thereby enabling continuous SCG monitoring. This study presents a feasible approach for flexible SCG acquisition in daily life scenarios and provides experimental evidence supporting the application of flexible sensors in home-based health monitoring.