Triboelectricity and static electricity are a very common phenomenon. Because it is difficult to collect and use, it is often a form of energy that is ignored by people. Since the invention of the friction nano-generator (TENG) by Wang Zhonglin of the Beijing Institute of Nano-Energy and Systems, Chinese Academy of Sciences in 2012, scholars around the world have conducted extensive research on TENG from various aspects. The key to the practical application of TENG as an energy device is to further increase the power density, and its core lies in the improvement of the friction charge density. Triboelectric charge density is one of the core performance indexes of triboelectric nanogenerators. Since TENG came out seven years ago, researchers have done a lot of research on friction material selection, surface modification and modification to improve the triboelectric charge density. The Institute of Nano-Energy Wang Jie and Wang Zhonglin's team increased the triboelectric charge density of TENG from 30 μC m-2 to nearly 300 μC m-2 through fragmentation and flexible contact methods (Nature communications 2016, 7, 12744), but the charge density is still Limited by air breakdown, an ultra-high charge density of 1003 μC m-2 was subsequently achieved in a high vacuum environment (Nature communications 2017, 8, 88). But usually, the friction nanogenerator works under atmospheric pressure, so most of the charge density here is released by air breakdown. If the energy of this part of air breakdown is collected, it can not only increase the output of the friction nanogenerator Performance, but also a new understanding of the friction nano-generator, is of great significance for better understanding and using the friction nano-power generation technology.
The traditional friction nano-generator has two inherent characteristics: AC output and pulse characteristics. Therefore, in general, the friction nanogenerator cannot directly drive electronic devices. The traditional method is to connect a full-wave rectifier bridge and energy storage unit to obtain a stable DC output, which is not conducive to building a miniaturized self-driving system. Moreover, the pulse output of the friction nano-generator has a relatively high loss factor (defined as the ratio of the current peak to its root mean square), which affects its efficiency for energy storage and driving electronic devices to a certain extent.
On April 5th, Wang Jie, Wang Zhonglin and others published a research paper entitled "A constant current triboelectric nanogenerator arising from electrostatic breakdown" in Science Advances. Liu Di, Yin Xing and Georgia Ph.D. students Guo Hengyu, a postdoctoral fellow in the Institute of Technology, is the co-first author of the paper.
The paper reported a new generation of friction nano-generators based on triboelectric charging and dielectric breakdown. For the first time, a constant current electrical output based on triboelectric charging and air breakdown was achieved. The basic principle is similar to the artificial generation and collection of "lightning" energy of. At the same time, the friction charge density is higher than the charge density of the conventional friction nano-generator limited by the breakdown of air in the atmospheric environment. This novel DC friction nanogenerator has been proven to directly drive electronic devices without the need for an external rectifier bridge or energy storage unit. The results of the research not only help to promote the miniaturization of self-driven systems for wearable electronics and Internet of Things systems, but also provide a new paradigm for the efficient collection of mechanical energy.
Figure: (a) The working principle of the constant current friction nano-generator, (b) The constant current output of the TENG, (c) The TENG directly drives the electronic watch (no rectification and energy storage unit)
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