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-c) is a fatal flaw due to the depolarization phenomenon. However, in this study, we find the low T-c would be a benefit for flexible piezoelectric sensors because small alterations of force trigger large changes in polarization. BaTi0.88Sn0.12O3 (BTS) with high piezoelectric coefficient and low T-c 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-1 and current sensitivity of 41.0 nA N-1. 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 superfiexible, 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.

Automated summary

The study reveals the advantage of low Curie temperature in flexible piezoelectric sensors, which enables large polarization changes with small alterations of force. The high piezoelectric coefficient and low T-c of BaTi0.88Sn0.12O3 (BTS) make it a suitable material for this purpose. Self-powered sensors based on BTS-GFF/PVDF composites demonstrate outstanding performance in detecting tiny forces in the low force region.