Contents lists available at ScienceDirect Nano Energy journal homepage: www.elsevier.com/locate/nanoen Communication Self-powered wireless optical transmission of mechanical agitation signals Wenbo Ding a,1 , Changsheng Wu a,1 , Yunlong Zi a,b,1 , Haiyang Zou a , Jiyu Wang a,c , Jia Cheng a,d , Aurelia C. Wang a , Zhong Lin Wang a,e,f, ⁎ a School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332, United States b Department of Mechanical and Automation Engineering, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China c State Key Laboratory of Power Transmission Equipment and System Security and New Technology, Chongqing University, Shapingba, Chongqing 400044, PR China d State Key Laboratory of Tribology, Department of Mechanical Engineering, Tsinghua University, Beijing 100084, PR China e Beijing Institute of Nanoenergy and Nanosystems, Chinese Academy of Sciences (CAS), Beijing 100083, PR China f CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology (NCNST), Beijing 100190, PR China ARTICLE INFO Keywords: Self-power Optical wireless transmission Mechanical sensing Triboelectric nanogenerators ABSTRACT The ubiquitous sensors have accelerated the realization of Internet of Things (IoT) but also raised challenges to the current overcrowding radio frequency (RF) based communications. The optical wireless communication (OWC) that utilizes the wide optic bandwidth can well solve the spectrum crisis and is an appealing com- plementary solution to the IoT applications. However, the additional direct current (DC) power supply and complicated modulating and power management circuits may limit the large-scale deployment of OWC systems. In this paper, by integrating with triboelectric nanogenerators (TENGs), the light-emitting diode (LED) could be directly transformed into a wireless transmitter that conveys the information associated with mechanical stimuli without additional power supply. With the customized TENG devices and the help of advanced image processing and machine learning techniques, three demonstrations with functions of optical remote control, pressure sensing, and security authentication, were demonstrated. The concept and results in this paper may greatly broaden the application of IoT through the integration of OWC and TENG. 1. Introduction With the popularity of Internet of Things (IoT), the ubiquitous ex- istence of sensors has brought great convenience to daily life, but it also raised serious challenges to the wireless communication access [1–3]. Current solutions for IoT communications are dominated by traditional radio frequency (RF) based techniques, e.g., the wireless local area networks (WLAN), Cellular, Bluetooth, Zigbee, and Radio-frequency identification (RFID) and etc. [4–8]. However, the RF band of the electromagnetic spectrum is fundamentally limited in capacity and costly since most sub-bands are exclusively licensed, resulting in spec- trum crisis especially in the scenarios with dense sensors [9,10]. In this context, the optical wireless communications (OWC) which utilizes the huge and unlicensed optic bandwidth for data transmission, provides a promising alternative to alleviate the spectrum crisis [11–13]. Besides, the OWC technology has many other attractive features such as worldwide availability, radiation-free, and high-capacity, and thus is regarded as an appealing complementary communication solution for IoT applications [14]. According to the different optical carriers used by transmitters, OWC can be categorized into three main types, i.e., visible, infrared (IR) and ultraviolet (UV) light communications [15–17]. The OWC can also be classified based on the receiver types, including the photo detector and camera based methods [18,19]. Nevertheless, existing OWC transmitters usually rely on direct current (DC) power supply, which induces high maintenance cost and limits its applications where only the event trigger is needed to monitor. To the best knowledge of the authors, there is no appealing scheme to address this problem. The triboelectric nanogenerator (TENG) first invented by Wang et al. in 2012, is an emerging mechanical energy harvesting technology as well as the mechanosensing technique that originates from the displacement current in the Maxwell's equations and can easily produce high-voltage up to thousands of volts [20–26]. Such characteristics make it ideal for powering the light-emitting diodes (LEDs) that have a threshold for operation voltage but require only a small amount of current. For ex- ample, a small TENG device (size of 1 in. × 1 in.) can easily light up tens of LEDs with a simple contact and separate operation [27]. Therefore, the TENG may be employed as a competitive power supply https://doi.org/10.1016/j.nanoen.2018.03.044 Received 18 January 2018; Received in revised form 26 February 2018; Accepted 14 March 2018 ⁎ Corresponding author at: School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332, United States. 1 These authors contributed equally to this work. E-mail addresses: wenbo.ding@mse.gatech.edu (W. Ding), changsheng.wu@gatech.edu (C. Wu), yunlongzi@gmail.com (Y. Zi), hzou8@gatech.edu (H. Zou), jiyu.wang@mse.gatech.edu (J. Wang), jia.cheng@gatech.edu (J. Cheng), aurelia.wang0@gmail.com (A.C. Wang), zhong.wang@mse.gatech.edu (Z.L. Wang). Nano Energy 47 (2018) 566–572 Available online 15 March 2018 2211-2855/ © 2018 Elsevier Ltd. All rights reserved. T