Flexible nanogenerators for wearable electronic applications based on piezoelectric materials

Wearable electronics-based devices have attracted significant attention with the rapid development of artificial intelligence (AI) and the Internet of Things (IoT) technologies. Taking advantage of the flexibility, lightweight features, reliability, and sensitivity offered by the wearable electronics technology, piezoelectric version of nanogenerator shows great potential as the human health monitoring sensor and biomechanical energy harvester for these wearable electronics. Considering this, we herein provide a progress report about the latest development of flexible piezoelectric nanogenerators. The internal mechanism of piezoelectricity in relation with the crystallography is presented. The enhancement in the output performance, which focuses on the optimization of materials and structures, is then reviewed and discussed to timely summarize the development of flexible piezoelectric nanogenerators. The application of flexible piezoelectric nanogenerators for human health/movement monitoring and biomechanical energy harvesting will also be briefly summarized. Based on this current progress, the challenges and perspectives are outlined and discussed. By this review, we hope to illustrate the designing strategies and shed light on the future exploration of new materials, devices, and technologies based on piezoelectricity.