Rotating-Disk-Based Hybridized Electromagnetic−Triboelectric Nanogenerator for Sustainably Powering Wireless Traffic Volume Sensors Binbin Zhang, †,# Jun Chen, ‡,# Long Jin, † Weili Deng, † Lei Zhang, † Haitao Zhang, † Minhao Zhu, †,§ Weiqing Yang,* ,† and Zhong Lin Wang* ,‡,∥ † Key Laboratory of Advanced Technologies of Materials (Ministry of Education), School of Materials Science and Engineering, and § State Key Laboratory of Traction Power, Southwest Jiaotong University, Chengdu 610031, China ‡ School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, United States ∥ Beijing Institute of Nanoenergy and Nanosystems, Chinese Academy of Sciences, Beijing, China *S Supporting Information ABSTRACT: Wireless traffic volume detectors play a critical role for measuring the traffic-flow in a real-time for current Intelligent Traffic System. However, as a battery-operated electronic device, regularly replacing battery remains a great challenge, especially in the remote area and wide distribution. Here, we report a self-powered active wireless traffic volume sensor by using a rotating-disk-based hybridized nanogenerator of triboelectric nanogenerator and electromagnetic generator as the sustainable power source. Operated at a rotating rate of 1000 rpm, the device delivered an output power of 17.5 mW, corresponding to a volume power density of 55.7 W/m 3 (P d = P/V, see Supporting Information for detailed calculation) at a loading resistance of 700 Ω. The hybridized nanogenerator was demonstrated to effectively harvest energy from wind generated by a moving vehicle through the tunnel. And the delivered power is capable of triggering a counter via a wireless transmitter for real-time monitoring the traffic volume in the tunnel. This study further expands the applications of triboelectric nanogenerators for high-performance ambient mechanical energy harvesting and as sustainable power sources for driving wireless traffic volume sensors. KEYWORDS: hybridized electromagnetic−triboelectric nanogenerator, self-powered wireless sensor A imed at providing innovative services relating to different modes of transportation and traffic management, the operation of Intelligent Traffic System (ITS) intensely relies on accurate measurement of traffic-flow characteristics. A wireless traffic volume detector plays a critical role of obtaining the timely information on traffic-flow. 1,2 However, the current wireless traffic volume detectors are mainly powered by a tradi- tional power supply unit, such as batteries. Nevertheless, because of the limited lifetime and the potential environmental pollu- tion issue of the batteries, a sustainable and portable power source is highly desired for the traffic volume sensors, especially in remote areas, for real-time traffic volume monitoring. 3−5 Recently, ascribing to a coupling effect of contact electrification and electrostatic induction, the triboelectric nanogenerator (TENG) has been proven to be an effective and robust approach for ambient mechanical energy harvesting. 6−14 Mainly utilizing conventional polymer thin film materials, the TENG has been proven as a fundamentally green energy technology, featured as being simple, reliable, and cost-effective as well as highly efficient, and its performance is superior to other approaches of its kind. 15−24 However, as a complementary energy technology to the traditional electromagnetic generator (EMG), the TENG suffers from a relatively low current output compared to its voltage output, and a hybridization of the two could be a superior solution to this problem. In this regard, here, we designed a rotating-disk-based hybridized nanogenerator of EMG and TENG for high-performance mechanical energy harvesting. With a device diameter of 10 cm and a height of 1 cm at an operational rotation rate of 1000 rpm, the hybridized nanogenerator can produce output powers of 17.5 mW, corresponding to a volume power density of 55.7 W/m 3 , and the hybridized nanogenerator was demonstrated to continuously power a wireless traffic volume sensor by harvesting air flow energy aroused by a moving car in the Received: April 8, 2016 Accepted: May 27, 2016 Article www.acsnano.org © XXXX American Chemical Society A DOI: 10.1021/acsnano.6b02384 ACS Nano XXXX, XXX, XXX−XXX