An introduction to triboelectric nanogenerators

Today, there is a continuous rise in the requirement for upgraded healthcare systems that are self-driven, dynamic and very low in maintenance. With a steep rise in the evolution of devices and their applications, such as sensors, there is an increment in the supply of sustainable energy without the replacement and recharging of the installed charge storage devices. Among the various energy scavengers, triboelectric nanogenerators (TENGs) have garnered huge attention as they have a high instantaneous output power and can be developed from a broad selection of available materials, like aluminium (Al) and copper (Cu) metal films, fluorinated ethylene propylene (FEP), polytetrafluoroethylene (PTFE) and green materials like cellulose-based materials. TENGs have a great ability to convert extracted mechanical energies into electrical energies very effectively due to the coupling effects of contact electrification and electrostatic induction. They have tremendous potential in a diverse range of applications, such as medical therapies that include biomedical applications, energy scavenging and active sensing. TENGs are devices made of self-energizing materials that are non-polluting, long-lasting and small sized. They can be developed through inexpensive fabrication processes and are environmentally friendly. In this paper, the mechanism by which the triboelectric nanogenerators perform their applications and how strategies are being developed to improve their performance have been discussed. We have also discussed the future research directions that are being undertaken to advance development in this field. So far, TENGs have mainly been used as mechanical and chemical stimuli to detect sensors and as an electrical source for electronic equipment and devices. Most of the studies found in the literature have reported that TENGs are primarily focused on optimization of systems and circuit designs or on the application of TENGs. A thorough review of the fundamentals of TENGs has been presented here.