Tribophotonics: An emerging self-powered wireless solution toward smart city

With the development of the Internet of Things (IoT), big data, and 5th generation mobile networks (5G), the smart city has been rapidly advanced in these years. Among the smart city era, billions of widely distributed sensor nodes are demanded to detect physical signals, raising the challenges in the sustainable supply of the distributed power and the wireless transmission of the distributed signals. Here, the concept of tribophotonics represents a new research direction by using the electrostatic induction brought by triboelectric charges to tune or generate the optical or electromagnetic wave transmission, as coupling the triboelectricity with photonics. Triboelectricity brings the capabilities of energy harvesting and self-powered sensing from the mechanical motions, addressing the challenge of the power supply, and photonics can be modulated to transmit signals wirelessly without using cables, addressing the challenge of the wireless signal transmission. With the unified design of tribophotonic devices, an emerging fully-self-powered wireless sensing and transmission solution can be achieved through multiple technological routes following the general trends of functionality, miniatured integrability, wireless portability, and self-power-ability. This review discusses the realization methods, applications, challenges, and development trends of tribophotonics.