Superflexible and Lead-Free Piezoelectric Nanogenerator as a Highly Sensitive Self-Powered Sensor for Human Motion Monitoring.

For traditional piezoelectric sensors based on poled ceramics, a low curie temperature (T) is a fatal flaw due to the depolarization phenomenon. However, in this study, we find the low T would be a benefit for flexible piezoelectric sensors because small alterations of force trigger large changes in polarization. BaTiSnO (BTS) with high piezoelectric coefficient and low T close to human body temperature is taken as an example for materials of this kind. Continuous piezoelectric BTS films were deposited on the flexible glass fiber fabrics (GFF), self-powered sensors based on the ultra-thin, superflexible, and polarization-free BTS-GFF/PVDF composite piezoelectric films are used for human motion sensing. In the low force region (1-9 N), the sensors have the outstanding performance with voltage sensitivity of 1.23 V N and current sensitivity of 41.0 nA N. The BTS-GFF/PVDF sensors can be used to detect the tiny forces of falling water drops, finger joint motion, tiny surface deformation, and fatigue driving with high sensitivity. This work provides a new paradigm for the preparation of superflexible, highly sensitive and wearable self-powered piezoelectric sensors, and this kind of sensors will have a broad application prospect in the fields of medical rehabilitation, human motion monitoring, and intelligent robot.