Reversal mechanism of triboelectrification in steel-polymer frictional interface for in-situ monitoring of transfer films

The triboelectric behavior of metal sliding against polymer in triboelectric nanogenerators (TENGs) is highly affected by the friction condition. However, the electrification behavior of the friction interface and its evolutionary mechanism during friction are still unclear. Herein, the internal mechanism of the triboelectric behavior of the material transfer modulation interface when the steel slides against PTFE/PE/POM polymers is systematically investigated in a tribological way. Different from the electrification in the vertical contact-separation mode, the surface potential of the three polymers will evolve inversely with time during friction. The reason for the reverse evolution is classified as the induced effect after the transfer of the material with residual charge to the steel ball. The formation of the transfer film not only stabilizes and reduces friction but also induces the inversion of the potential of the substrate surface. By polishing the transfer film on the surface of the steel ball, the inversion of the surface potential can be repeated reproducibly. Furthermore, the existence of the transfer film is monitored in situ by monitoring the surface potential change of the steel ball. This work provides a vital reference for revealing the physical mechanism of interface triboelectrification and expanding the tribological characterization methods.