Manipulating the triboelectric surface charge density of polymers by low-energy helium ion irradiation/implantation

Triboelectric materials and their modification methods are the cornerstones for fabricating triboelectric nanogenerators (TENGs). Numerous modification methods have been proposed for TENGs, while a highly effective and long-term stable method is still under exploration. Here, a surface modification method using low-energy ion irradiation has been proposed for tuning the chemical structures and functional groups of triboelectric polymers at the molecular level. The low-energy ion irradiation brings negligible change to the surface roughness at the micro-scale and mechanical flexibility of the target polymer, while it can provide a stable modification of the electrification performance. Systematic studies about the chemical structure changes in four different polymers induced by ion irradiation can bring insight into the interaction between different chemical groups and electrification performance. A Kapton film modified by ion irradiation shows several unprecedented characteristics, such as high surface charge density, excellent stability and ultrahigh electron-donating capability, and not only creates a new record in the tribo series, but also provides a good demonstration for regulating electrification behavior based on controllable chemical structure change. This study can open up a series of possible breakthroughs in the production of triboelectric materials with diversified properties, which can promote the study of TENGs from a very fundamental level. Broader context With the fast development of the internet of things, a large number of sensors and microelectronic devices are applied for supporting this huge information network. Accordingly, this requires the united strength of both batteries and energy harvesting techniques to power all these mobile devices. Ever since 2012, triboelectric nanogenerators (TENGs) have gradually become the mainstream technique in the field of energy harvesting, due to their universal applicability, low cost and high efficiency. Triboelectric materials are the core elements for the fabrication of TENGs, while a highly effective and long-term stable modification method for triboelectric materials is still under exploration. In this study, based on a high-fluence ion irradiation technique, a different modification method has been proposed to directly manipulate the chemical bonds and functional groups of triboelectric polymers at the molecular level, which can change the polymer's `gene' for contact electrification. A triboelectric film modified by this method shows several unprecedented characteristics, such as ultrahigh electron-donating capability and excellent stability, and creates a new record in the tribo series. A variety of possible breakthroughs in the production of triboelectric materials with diversified properties can be expected based on the results of this study.