Wearable triboelectric nanogenerators for biomechanical energy harvesting

With compelling features of flexibility, conformability, and user friendliness, wearable bioelectronics have undergone tremendous development on account of miniaturization and multifunction advancements which could cater to the development trend of Internet of Things (IoT) and fifth-generation wireless technology. However, powering wearable bioelectronics sustainably and pervasively is beyond the capability of traditional power supply systems and remains a challenge and highly desired. By using the coupling effect of contact electrification and electrostatic induction, triboelectric nanogenerators (TENGs) were demonstrated to efficiently convert irregular and low-frequency biomechanical energy from human body movements into electrical energy for the sustainable powering of wearable bioelectronics. In this article, the latest representative achievements of wearable TENGs for electricity generation are comprehensively reviewed with the order of the accessible biomechanical energy on the human body from head to feet. This review not only covers the fundamental working mechanism, rational structural design, selection of the tribo-materials, and fabrication process of wearable TENGs, but also investigates the movement patterns and characteristics of each part of the body, as well as its feasibility and convenience for electricity generation. Finally, perspectives and challenges regarding wearable TENGs at present are discussed.