Flexible cavity CNT-doped PVDF triboelectric nanogenerator for dual-mode respiratory sensing

With the increasing prevalence of pulmonary diseases and the urgent need for continuous respiratory health monitoring, the development of wearable systems featuring high sensitivity, multidimensional signal acquisition, and self-powered operation has become critically important. Here, we report a dual-mode triboelectric nanogenerator (TENG)-based sensor that integrates a carbon nanotube (CNT)-doped polyvinylidene fluoride (PVDF) electrospun film with a deformable cavity support structure, enabling enhanced electrical performance and mechanical adaptability. The incorporation of CNTs facilitates the formation of the electroactive β-phase in PVDF, significantly boosting the triboelectric output, while the engineered cavity structure improves responsiveness to subtle biomechanical deformations. The device operates without any external power source and achieves a high sensitivity of 7.147 V/N. It is capable of simultaneously detecting two key physiological signals during respiration: airflow-induced stimuli near the mouth or nose, and mechanical deformation of the lower thoracic region (specifically the xiphoid area) caused by thoracoabdominal movement. The output signal exhibits a characteristic nested dual-peak waveform, clearly reflecting the complex mechanical dynamics of the breathing process. This work offers a promising strategy for the development of next-generation wearable respiratory monitoring systems, with potential applications in pulmonary rehabilitation, chronic respiratory disease management, and sleep-related breathing disorder assessment.