Piezoelectrets for wearable energy harvesters and sensors

Wearable electronics have attracted attention for their potential use in constructing a human-centered intelligent world. As one of the most promising materials for constructing high-performance self-powered wearable electronics, piezoelectrets possess the advantages of high flexibility, light weight, biocompatibility and high piezoelectric performance. Herein, recent advances in this area are reviewed. First, the mechanism, theoretical progress, and manufacturing techniques of piezoelectrets are presented. Then, devices based on different piezoelectret materials as human-body mechanical energy harvesters are introduced in sequence, and their major applications are demonstrated, including self-powered acoustic transducers, flexible pressure sensors and wearable physiological monitors. At the end of this review, the perspectives and challenges of piezoelectrets are discussed. We anticipate that traditional piezoelectrets with unique designs will play important roles in wearable energy harvesting and human physiological signal monitoring in the near future.