High Durable, Biocompatible, and Flexible Piezoelectric Pulse Sensor Using Single-Crystalline III-N Thin Film

Flexible pulse sensors that can detect subtle skin surface deformation caused by arterial pulses are key components for developing non-invasive continuous pulse waveform monitoring systems that provide vital health status parameters. Piezoelectric pulse sensors (PPSs) offer a promising solution for flexible pulse sensors due to their relatively high sensitivity and stability, and low power consumption, when compared with conventional active pulse sensors. However, the reported high-performance PPSs contain toxic lead, which limits their practical applications. In this study, a highly sensitive and flexible PPS that detects surface deflections on the micrometer scale is fabricated with single-crystalline group III-nitride thin film. This biocompatible flexible PPS is sensitive enough to detect pulse waveform with detailed characteristic peaks from most arterial pulse sites when attached to the skin surface without applying external pressure. Useful physiological parameters such as the pulse rate, artery augmentation index, and pulse wave velocity can be drawn from the as-acquired pulse waveforms. The flexible PPS can also be used to continuously monitor the arterial pulse waveform.