RESEARCH NEWS 1800588 (1 of 7) © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.advmattechnol.de The Current Development and Future Outlook of Triboelectric Nanogenerators: A Survey of Literature Tinghai Cheng, Qi Gao, and Zhong Lin Wang* DOI: 10.1002/admt.201800588 1. Introduction With the speedy development of sensor network, along with the increasing demand or wearable and ubiquitous “smart” devices, a tremendous quantity of small electronic devices has been widely applied all over the world. These small electronics include sensors, wireless transmitters, and/or actuators, etc. Generally, the power requirement for each of these small electronics is around milliwatt (mW) or micro- watt (μW) range, with features such as low cost, mobility, light-weight, and sustainability. A conventional and most commonly used approach to provide the power for these elec- tronics is installing batteries. Nevertheless, batteries have limited life spans. As the amount of the electronics increases Triboelectric nanogenerators are devices that effectively convert ambient mechanical energy into electricity, which can be used as a power source or a sensor signal. Since first proposed by Dr. Zhong Lin Wang in 2012, the development of triboelectric nanogenerators has grown rapidly. Herein, the development of the triboelectric nanogenerator and its global impact is investigated by analyzing the statistical publication numbers and the geographic distribution of the publications. In addition, this article also features the main applications of triboelectric nanogenerators such as blue energy, self-powered sensor/systems, and micro-/nanoenergy, and points out its future outlook. Several challenges and fundamental physical questions are also discussed to provide a more comprehensive view of this revolutionary technology. Triboelectric Nanogenerator dramatically, it has become much more difficult for the replacement, manage- ment, and/or recycling of the gigantic amount of batteries. To address these issues, the concept of “self-powered” has been proposed and attracted much attention. Another critical alternative is to harvest energy from the ambient environment to serve as power sources. The invention of the nanogenerator opens up new area for both energy harvesting and self-powered sensors applications. Therefore, in this article, we focus on discussing the cur- rent development and future of nano- generator, specifically triboelectric nanogenerator. The concept of “nano- generator” was introduced in 2006 for using piezoelectric nanowires for converting tiny mechan- ical triggering into electric output in order to realize the self-powering proposed by Wang. [1,2] In the January of 2012, another type of nanogenerator, tribo- electric nanogenerator (TENG), that can also harvest ambient mechanical energy by combining contact-electrification and electrostatic induction was invented by our research group as well. [3–5] TENG has four basic modes: Figure 1a vertical con- tact-separation mode, Figure 1b in-plane contact-sliding mode, Figure 1c single-electrode mode, and Figure 1d freestanding tri- boelectric-layer mode. [6] Since then, the development of TENG technologies grows and expands rapidly. Moreover, the power density of a TENG, which depends on the device structure and active materials, has been reported to be up to 500 W m -2 . [7] In this article, we focus on and discuss the current development and future prospect of TENG. By now, nanogenerators repre- sent a technology that use Maxwell’s displacement current for energy harvesting. [8] 2. Data Collection and Analysis To demonstrate the growing tendency of the TENG field, herein, we run search queries using common keywords that related to the TENG research in the Web of Science data- base, with AND operator(s) between keywords. The keywords include triboelectric nanogenerator; TENG; triboelectric generator; triboelectric (AND) triboelectrification (AND) electrostatic induction; triboelectric (AND) nanogenerator; triboelectric (AND) generator; triboelectric (AND) sensor; tri- boelectric (AND) energy harvesting; triboelectric (AND) energy Dr. T. H. Cheng, Prof. Z. L. Wang School of Materials Science and Engineering Georgia Institute of Technology Atlanta, GA 30332-0245, USA E-mail: zlwang@gatech.edu Dr. T. H. Cheng, Q. Gao School of Mechatronic Engineering Changchun University of Technology Changchun, Jilin 130012, P. R. China Prof. Z. L. Wang Beijing Institute of Nanoenergy and Nanosystems Chinese Academy of Sciences Beijing 100083, P. R. China The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/admt.201800588. Adv. Mater. Technol. 2019, 1800588