Dynamics of contact electrification

Abstract

Although the electrical charging of objects brought into contact has been observed for at least 2000 years, the details of the underlying mechanism are still not yet fully understood. The present paper deals with the very basic process of contact electrification between two metals. We have developed an experimental method to follow the charge of a small sphere bouncing on a grounded planar electrode on a time scale down to 1 μs. It reveals that the sphere is discharged in the moment of contact, which lasts about 6 to 8 μs. However, at the very moment of disruption of the electrical contact, it regains charge far beyond the expectation according to the contact potential difference. The excess charge rises with increasing contact area.

Artificial Intelligence-Enabled Caregiving Walking Stick Powered by Ultra-Low-Frequency Human Motion

“…Below the EMG lies an R-TENG, which is utilized to detect gait abnormality from the irregular rotation motions. For self-powered TENG sensors, they are working based on the coupling effect of contact electrification (triboelectrification) to convert the mechanical stimuli to electric output, while the output signal is relative to the potential differences of applied materials, contact force and speed, contact area, etc . And the components and working mechanisms for each part are discussed in detail in Note S1 (Supporting Information).…”

Study of Contact Electrification at Liquid-Gas Interface

“…The phenomenon of surface electrification upon contact has been documented for over 2600 years, and many applications have been developed based on this phenomenon. − Since 2012, the triboelectric nanogenerator (TENG) proposed by Wang, which uses the coupling of contact electrification and electrostatic induction to generate electrical energy, has been a further understanding of the mechanism of frictional power and gradually developing as one technology in the field of energy harvesting. − The operation of a TENG mainly relies on the interfacial electrostatic field, which outputs power due to the displacement current induced by mechanical motion. − So far, TENGs can harvest energy from tribo-contacts at the solid-solid interface, − solid-liquid interface, − liquid-liquid interface, , and even solid-gas interface, while the applications of TENGs have also been successfully developed in many areas, including micro/nano power source, − self-powered sensors, − blue energy harvester, − and high-voltage sources. − However, little progress has been proposed related to energy generation at the liquid-gas (L-G) interface. It is commonly known that lightning on rainy days and lightning of dressing coats are the results of triboelectricity, which can be an undeveloped energy source.…”

Hot Carrier Transport and Carrier Multiplication Induced High Performance Vertical Graphene/Silicon Dynamic Diode Generator

“…Then, due to the ultrafast carrier transport in the dynamic graphene/silicon Van der Waals heterojunction, those hot carriers were transmitted to the graphene membrane in a microsecond time scale. [ 20 ] Finally, those hot carriers were effectively collected in the graphene membrane with an ultralong hot electron lifetime. In comparison, the horizontal graphene/silicon DDG generated a constant voltage under continuous movement, but this was significantly lower than the vertical graphene/silicon DDG, as shown in Figure S3 (Supporting Information).…”

“…To systematically explore the hot carrier dynamic processes of the vertical graphene/silicon DDG, the entire generation, transport, and collection processes of hot carriers are illustrated, which reveal how the hot carriers of graphene in dynamic heterojunction interfaces can be effectively utilized. When the graphene and silicon are in vertical contact, electrons diffuse from the higher Fermi level graphene to the lower Fermi level silicon and form a static depletion region in the microsecond time scale, [ 20 ] generating a voltage as high as 1.5 V. Following the vertical separation of the graphene and silicon, the dynamic equilibrium of the depletion region is disrupted and diffusion carriers are released and rebound to graphene and silicon, generating an opposite voltage output. The voltage is significantly higher than the barrier height of the graphene/silicon heterojunction.…”