Pulse sensor for cardiovascular health monitoring based on self-poled piezo-tribo hybrid composites

Wearable devices, such as a pulse sensor, can be useful for real-time monitoring of cardiovascular health. Continuous and systematic monitoring of cardiovascular parameters can predict conditions such as coronary artery disease, heart failure, cardiac arrest, etc. However, most commercial wearable sensors are typically limited to macroscopic metrics such as heart rate and SpO₂. This work introduces a sensitive piezoelectric-triboelectric hybrid composite-based pulse sensor that provides insight into an individual's cardiovascular health by measuring heart rate variability (HRV) metrics, including heart rate, P-P intervals (the time between successive heartbeats), and RMSSD (the root mean square of successive differences between intervals). The high sensitivity of the sensor is rooted in a dual strategy: first, the piezoceramic BaTi_0.94Sn_0.06O₃ (BST6) is engineered at a morphotropic phase boundary, yielding an excellent piezoelectric coefficient of . Second, the device employs a layer-by-layer configuration incorporating a self-poling PDMS-MWCNT interfacial layer sandwiched between the PDMS-BST6 hybrid composite layers. This layered architecture facilitates self-poling by enhancing charge collection at the PDMS-MWCNT layer while suppressing recombination at the PDMS-BST6 hybrid composite layer. Further, Short-Time Fourier Transform (STFT) and Dynamic Time Warping (DTW) analyses of the recorded pulse wave suggest device stability over 100 days and evaluate heart condition. This study opens the scope for an IoT-enabled wearable system for long-term, real-time cardiovascular health monitoring and assessment.