Fig. 1.
Contact electrification and air breakdown. a Phenomena of contact electrification in nature, such as lighting and triboelectrification of rubber rod and fur. b Applications of triboelectric nanogenerators (TENGs) for driving electronic devices, such as electric bulb, fitness tracker, electric watch, health monitor, temperature-humidity meter, and cell phones. c Working mechanism of contact-separation TENG. d Finite-element simulation of the potential distribution between two triboelectric materials, copper and polytetrafluoroethylene (PTFE) with a gap distance of 1 cm and a surface charge density of 50 µC m−2 using COMSOL. e Output charge density of TENG after ion air injection. Top insert shows schematic of gap voltage (V gap) between the metal electrode and the dielectric film, which could cause the breakdown of the air; bottom-left insert records the in situ measurement of the charge flow from the ground to the bottom electrode of the PTFE film during the step-by-step ion injection process; bottom-right insert plots the charge transfer between the two electrodes of TENG operating after the ion injection. f Air breakdown voltage at different pressures and gap voltage of TENG with different charge densities. The thickness of PTFE film is 200 µm