Finger typing driven triboelectric nanogenerator and its use for instantaneously lighting up LEDs Q2 Q1 Q3 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 55 57 59 61 Q4 Available online at www.sciencedirect.com journal homepage: www.elsevier.com/locate/nanoenergy Nano Energy (]]]]) ], ]]]–]]] 2211-2855/$ - see fro http://dx.doi.org/1 �Corresponding a Engineering, Georgia USA. ����Correspondin E-mail addresse jun.zhou@mail.hust. Please cite this art LEDs, Nano Energy RAPID COMMUNICATION Finger typing driven triboelectric nanogenerator and its use for instantaneously lighting up LEDs Junwen Zhonga, Qize Zhonga, Fengru Fanb, Yan Zhangb,c, Sihong Wangb, Bin Hua, Zhong Lin Wangb,c,�, Jun Zhoua,���� aWuhan National Laboratory for Optoelectronics (WNLO), and School of Optical and Electronic Information, Huazhong University of Science and Technology (HUST), Wuhan, 430074, PR China bSchool of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0245, USA cBeijing Institute of Nanoenergy and Nanosystems, Chinese Academy of Sciences, Beijing, China Received 27 November 2012; accepted 28 November 2012 KEYWORDS Nanogenerator; Self-powered system; Flexible nt matter & 2012 0.1016/j.nanoen.2 uthor at: School Institute of Techno g author. Tel.: +86 s: zhong.wang@m edu.cn (J. Zhou). icle as: J. Zhong, (2012), http://dx Abstract Harvest mechanical energy with variable frequency and amplitude in our environment for building self-powered systems is an effective and practically applicable technology to assure the independently and sustainable operation of mobile electronics and sensor networks without the use of a battery or at least with extended life time. In this study, we demonstrated a novel and simple arch-shaped flexible triboelectric nanogenerator (TENG) that can efficiently harvesting irregular mechanical energy. The mechanism of the TENG was intensively discussed and illustrated. The instantaneous output power of single TENG device can reach as high as�4.125 mW by a finger typing, which is high enough to instantaneously drive 50 commercial blue LEDs connected in series, demonstrating the potential application of the TENG for self-powered systems and mobile electronics. & 2012 Published by Elsevier Ltd. 63 65 67 69 Introduction Recently, research on light-weight, flexible, and even wear- able electronics have attracted much attention for its poten- tial applications including but not limited to, wearable display, 71 73 75 Published by Elsevier Ltd. 012.11.015 of Materials Science and logy, Atlanta, GA 30332-0245, 13307198060. se.gatech.edu (Z.L. Wang), et al., Finger typing driven tribo .doi.org/10.1016/j.nanoen.2012. artificial electronic skin, and distributed sensors [1,2]. A key component for these applications is the power source that is as flexible as the electronic sheet itself. Harvesting energy from ambient energy source including solar, thermal energy and mechanical energy could assure the independent and sustainable operating of such systems without the use of a battery or at least extending the life time of a battery [3–5]. Irregular mechanical energy, including ambient noise, airflows and activity of the human body, is probably the most common energy sources in our living environment and almost available anywhere at any time, which could be an ideal source of energy for mobile electronics. Piezoelectric 77 electric nanogenerator and its use for instantaneously lighting up 11.015 dx.doi.org/10.1016/j.nanoen.2012.11.015 dx.doi.org/10.1016/j.nanoen.2012.11.015 dx.doi.org/10.1016/j.nanoen.2012.11.015 mailto:zhong.wang@mse.gatech.edu mailto:jun.zhou@mail.hust.edu.cn dx.doi.org/10.1016/j.nanoen.2012.11.015 dx.doi.org/10.1016/j.nanoen.2012.11.015 dx.doi.org/10.1016/j.nanoen.2012.11.015 dx.doi.org/10.1016/j.nanoen.2012.11.015 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 55 57 59 61 63 65 67 69 71 73 75 77 J. Zhong et al.2 nanogenerators (PNGs) [6–16] and triboelectric nanogenera- tors (TENGs) [17–20] have been developed to harvest irregular mechanical energy with variable frequency and amplitude in our environment based on the piezoelectric effect and triboelectric effect, and they have been demon- strated to power small electronic devices, such as a small liquid crystalline display (LCD) screen [21] and electrochro- mic device [22]. Here we demonstrate a novel and simple design of the TENG for efficiently harvesting mechanical energy. A fingertip typing can generate an output voltage of up to�125 V, and the output power is sufficient to lit up 50 LEDs connected in series. By conjunct with a transformer for enhancing the output current, the TENG can power a commercial infrared transmitter with an output current of�6 mA at�1 V. Our study unambiguously demonstrates the application of the TENGs for self-powered system. 79 81 83 85 87 Experimental Fabrication of the TENG The design of the TENG is presented in Figure 1a. The fabrication process started with a rectangular (3.5 cm �2.5 cm) polytetrafluoroethylene (PTFE) film (0.20 mm in Figure 1 (a) Schematic diagram and digital photography of an arch (b) PTFE film and (c) Ag coated PVA nanowires on PET film. Inset show circuit of the TENG with an external load of R when the device is corresponding current–time curve, respectively. (h) Linear superpos the same polarity (G1+G2) and opposite polarity (G1�G2). Please cite this article as: J. Zhong, et al., Finger typing driven tribo LEDs, Nano Energy (2012), http://dx.doi.org/10.1016/j.nanoen.2012. thickness, Figure 1b). Cu layer (200 nm) was deposited on the upper surface of PTFE by sputter coating, and used as the top electrode. Specially, the Cu-coated PTFE film will be bent toward the polymer side because of the large differ- ence in thermal expansion coefficients, which results in an arch-shape structure. Then PTFE side of the hybrid film was placed onto another rectangular (3.5 cm�2.2 cm) poly- ethylene glycol terephthalate (PET) film (0.22 mm in thick- ness). The inner surface of PET film was coated with PVA nanowires prepared by electrospining, and then deposited with a thin Ag layer (100 nm in thickness) by sputter coating as the bottom electrode (Figure 1c). Before assembling of the device, the inner surface of the PEFE film was rubbed with cellulose paper to charging the surface of PTFE film. According to the triboelectric series, [23] that is, a list of materials based on their tendency to gain or lost charges, electrons are injected from cellulose paper to PTFE, resulting in net negative charges (Q) on the PTFE surface. It is reported that PTFE can contain charge densities up to�5�10�4 C/m2 with theoretical lifetimes of hundreds of years [24,25]. During the assembling process, the inner surface of the PTFE film faced Ag layer of the PET film, then the edges of the two films along the length axis were fixed by Kapton tape, forming an arch-shaped device (inset of Figure 1a). 89 91 93 95 97 99 101 103 105 107 109 111 113 115 117 119 121 123 -structured flexible triboelectric nanogenerator. SEM images of s the EDS spectrum of the Ag coated PVA nanowires. Equivalent at (d) origin, (e) pressing and (f) releasing states and (g) the ition tests of two TENGs (G1 and G2) connected in parallel with electric nanogenerator and its use for instantaneously lighting up 11.015 dx.doi.org/10.1016/j.nanoen.2012.11.015 dx.doi.org/10.1016/j.nanoen.2012.11.015 dx.doi.org/10.1016/j.nanoen.2012.11.015 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 55 57 59 61 63 65 67 69 3Finger typing driven triboelectric nanogenerator Results and discussions Power generation mechanism of TENG In a simplified model, the equivalent circuit of the TENG with an external load of R is illustrated in Figure 1d, f and g, in which the device can be regarded as a flat-panel capacitor. As the inner surface of the PTFE was charged Figure 2 Electrical performance characterization measurement current–time curve and (b) maximum output current as well as the frequency of 3 Hz and external load resistance of 500 MO. (c) Outpu total charges transported at different stimulation frequencies at a 500 MO. (e) Stimulations and variation with different degrees of d (f) Maximum output current and instantaneous peak power as a funct of 3 Hz and deformation of 1.5 mm. Please cite this article as: J. Zhong, et al., Finger typing driven tribo LEDs, Nano Energy (2012), http://dx.doi.org/10.1016/j.nanoen.2012. with negative charges of Q while the Cu electrode was grounded, the Cu electrode and Ag electrode would produce positive charges of Q1 and Q2, respectively, due the electro- static induction and conservation of charges, where �Q=Q1+Q2 at any moment. Assuming that the charges distributed is uniformly on the surface of PTFE, Cu and Ag, thus �s¼s1þs2 ð1Þ 71 73 75 77 79 81 83 85 87 89 91 93 95 97 99 101 103 105 107 109 111 113 115 117 119 121 123 of a TENG under different experiment conditions. (a) Output total charges transported at different deformations for a given t current–time curve and (d) maximum output current as well as given deformation of 1.5 mm and external load resistance of eformation provided by the mechanical trigger to the TENG. ion of the external load resistance at a given bending frequency electric nanogenerator and its use for instantaneously lighting up 11.015 dx.doi.org/10.1016/j.nanoen.2012.11.015 dx.doi.org/10.1016/j.nanoen.2012.11.015 dx.doi.org/10.1016/j.nanoen.2012.11.015 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 55 57 59 61 63 65 67 69 71 73 75 77 79 81 83 85 87 89 91 93 95 J. Zhong et al.4 where s is the charge density of PTFE surface, s1 is charge density of Cu surface which is contacted with PTFE and s2 is charge density of Ag upper surface (Figure 1d). If we define electric potential of the top electrode as UTE and electric potential of bottom electrode as UBE, then at any equilibrium state (Figure 2b) UBE can be presented as follows [20]: UBE ¼ s2 2e0 d2þ s2 2erpe0 d1þ s 2erpe0 d1� s 2e0 d2 � s1 2e0erp d1� s1 2e0 d2 ¼UTE ¼0 ð2Þ where e0 is the vacuum permittivity, and erp is the relative permittivity of PTFE, d1 is the thickness of PTFE film, d2 is the distance between the two electrodes. Put Eq. (1) into Eq. (2), we can get sd2þs1d2þ s1 erp d1 ¼0 ð3Þ s1 ¼� s 1þd1=d2erp ð4Þ As d1 and erp are constant with value of 0.2 mm and �1.93, [25] respectively, and charge Q is stable for a relatively long time on the PTFE surface, thus s1 is dictated by the gap distance d2 (See Figure S2). The variation of d2 will result in the redistribution of the charges between Cu and Ag electrodes through the load R which generates a current through the load, so that mechanical energy is converted into electricity. The working mechanism of the TENG is similar to a variable-capacitance generator [26–28] except that the bias is provided by the triboelectric charges rather than an external voltage source. Once the TENG was being pressed (Figure 1e), a reduction of the interlayer distance of d2 would make the decrease s1 according to Figure 3 TENG as a direct power source to drive 50 commercia harvesting circuit and LED display. (b) Current–voltage curve of the 5 of the prototype energy harvesting circuit and LED display. (c) The r a finger typing. (f) The magnified current peak and the correspond Please cite this article as: J. Zhong, et al., Finger typing driven tribo LEDs, Nano Energy (2012), http://dx.doi.org/10.1016/j.nanoen.2012. Eq. (4) (See Figure S1), which results in an instantaneous positive current (Figure 1g) (here we defined a forward connection for the measurement as a configuration with positive end of the electrometer connected to the top electrode). Upon the TENG was being released (Figure 1f), the device would revert back to its original arch shape due to resilience, the interlayer distance d2 would increase, and the surface charge s1 increased as well, resulting in an instantaneous negative current (Figure 1g). The output performance of TENG The output of the TENG was carefully studied by periodi- cally bending and releasing at a controlled frequency and amplitude. The measuring system is schematically shown in Figure S2. One end of the TENG was fixed on a x–y–z mechanical stage that was fixed tightly on an optical air table, with another end free to be bend. To rule out the possible artifacts, we did the measurement of the output current when two TENG were connected in parallel with an external load of 500 MO and the results are shown in Figure 1h. When two TENGs were connected in the same direction, the total output current was enhanced. In comparison, when two TENGs were connected in antipar- allel, the total output current was decreased. The results indicated that the electrical output of the TENGs satisfied linear superposition criterion in the basic circuit connec- tions [18]. The output current of a TENG variation with different degree of deformations (the amplitude of the pushing down distance of the mechanical trigger) are depicted in the Figure 2a. Correspondingly, for a given frequency of 3 Hz and external load resistance of 500 MO, an increase of 97 99 101 103 105 107 109 111 113 115 117 119 121 123 lized blue light emitting diodes. (a) Schematic of the energy 0 LEDs connected in series. Inset shows the digital photography ectified output current through 50 LEDs driven by the TENG with ing snapshots of the TENG-driven flashing LED display. electric nanogenerator and its use for instantaneously lighting up 11.015 dx.doi.org/10.1016/j.nanoen.2012.11.015 dx.doi.org/10.1016/j.nanoen.2012.11.015 dx.doi.org/10.1016/j.nanoen.2012.11.015 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 55 57 59 61 63 65 67 69 71 73 75 77 79 81 83 85 87 89 91 5Finger typing driven triboelectric nanogenerator deformation generally increased the magnitude of the maximum current, from 0.25 mA at 0.5 mm to 0.72 mA at 2 mm. The integration of each current peak can gives the total chargers transferred between the electrodes, as shown in Figure 2b, indicating that the total amount charges transferred increased with the increase of distance change between the two electrodes, which is consisted with our model discussed above. Figure 2c shows the output current of the TENG under stimulation frequencies ranging from 1 to 4 Hz for a given deformation distance (1.5 mm) and external load resistance (500 MO), revealing a clear increasing trend with the increase of frequency. For a given deformation, as the deformation rate increases with stimulation frequency, which leads to a higher flow rate of charges, resulting in a higher current peak value, however the total amount of the charges transferred is constant. The integration of each current peak from each of the 4 different stimulation frequency are shown in Figure 2d, indicating that the total amount of the charges transferred almost keep constant of�21 nC at a given deformation. Therefore, the instanta- neous power output increases with the increase of stimula- tion frequency. The output current and voltage of a TENG variation with different external load for a given frequency of 3 Hz and degree of deformation (1.5 mm) are depicted in Figure 2e. With an increase in the load resistance, the maximum current decreases, while the voltage across the following an opposite trend with the maximum value of�407 V. ITD A + - Figure 4 (a) Schematic of an infrared transmitter–receiver system TENG in conjunct with a transformer. L2 is the infrared receiver d external load connected with IRD with a value of 20 M. (b) The outpu time when ITD was driven by TENG in conjunct with a transformer Please cite this article as: J. Zhong, et al., Finger typing driven tribo LEDs, Nano Energy (2012), http://dx.doi.org/10.1016/j.nanoen.2012. The output power exhibits an instantaneous peak value of 0.23 mW with an external load of 300 MO (Figure 2f). The measurement results reveal that the TENG is particularly efficient provided that the load has a resistance on the order of hundreds of megaohm. The electric energy pro- duced by our TENG can be stored and using a rectifier and capacitor, and also can be used as a direct power source without electric storage to power commercial LEDs (Video 1 and Figure S3). Supplementary material related to this article can be found online at http://dx.doi.org/10.1016/j.nanoen.2012. 11.015. Powering 50 LEDs in series by TENG directly As a demonstration of converting irregular mechanical energy, such as human motion into electricity to power electronics, our TENG was successfully used as a direct power source without an energy storage system to instantly power 50 commercial blue LEDs (3B4SC) connected in series with a finger typing! Figure 3a and inset of Figure 3b show the schematic and digital photography of the prototype energy harvesting circuit and LED display. A bridge rectifier is used to convert the AC output signals into DC signals. 50 LEDs are connected in series, and 26 LEDs in the first row forms characters of ‘‘HUST’’, while 24 LEDS in the second row forms characters of ‘‘WNLO’’. Figure 3b shows the current–voltage (I–V) curve of the 50 LEDs connected in 93 95 97 99 101 103 105 107 109 111 113 115 117 119 121 123 RIRD V 4.74 V in which the infrared transmitter diode (ITD, L1) was driven by a iode (IRD) as a receiver to detect the light from the ITD. R is t current through the ITD and (c) the voltage drop across R with under finger typing. electric nanogenerator and its use for instantaneously lighting up 11.015 dx.doi.org/doi:10.1016/j.nanoen.2012.11.015 dx.doi.org/doi:10.1016/j.nanoen.2012.11.015 dx.doi.org/10.1016/j.nanoen.2012.11.015 dx.doi.org/10.1016/j.nanoen.2012.11.015 dx.doi.org/10.1016/j.nanoen.2012.11.015 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 55 57 59 61 63 65 67 69 71 73 75 77 79 81 83 85 87 89 91 93 95 97 99 101 103 105 107 109 111 113 115 117 119 121 123 J. Zhong et al.6 series, revealing the forward turn-on voltage of�125 V. In our study, both the finger pressing and releasing process could light the LEDs (See Video 2 and inset of Figure 3d), and the corresponding output current through the LEDs were simultaneously recorded and shown in Figure 3c. It is observed that the current peak corresponding to releasing process has a smaller magnitude but lasts longer than that for pressing process (Figure 3d). Such an observation can be explained by the fact that pressing is caused by finger typing, while it is the resilience of the arch-shaped PTFE film that leads to the releasing. Therefore, it is very likely that releasing corresponds to a slower process and thus a smaller but wider current signal. The highest peak current went across the LEDs was �33 mA, corresponding to an instantaneous output power of�4.125 mW. TENG used in wireless system In addition, by conjunction with a transformer that is a passive device, high output current in the order of mili- amperes was generated by our TENG that could be used to power those electronic devices which work with high current. Figure 4a shows the schematic of an infrared transmitter–receiver system (ST188, L4). The infrared trans- mitter diode (ITD) (forward turn-on voltage of�1 V, Figure S4) was powered by a TENG conjunct with a transformer, while infrared receiver diode (IRD) and external load R (20 MO) were powered by a constant power source. When the ITD was driven by TENG which was triggered by finger typing, a strong infrared signal would emitted from the ITD, as the IRD received the infrared signal, the resistance of the IRD would decrease and leading to an obvious change of voltage across the external load R. In our study, the output current through the ITD and the voltage drop across R with time was monitored simultaneously, and are shown in Figure 4b and c, respectively. Figure 4b depicts the output current after applying the transformer can reach as high as �6 mA. The change of the voltage across the external load R has the same trend with the output current (Figure 4c). Conclusions In summary, a novel and simple arch-shaped TENG is invented that can efficiently used for harvesting irregular mechanical energy. The instantaneous output power of single TENG device can reach as high as�4.125 mW, which is high enough to instantaneously drive 50 commercial blue LEDs connected in series. By conjunct with a transformer, the TENG can power a commercial infrared transmitter with an output current of�6 mA. The TENGs have potential of harvesting energy from human motion, mechanical vibration and more, with great applications in self-powered systems for wearable electronics, sensors and security. Acknowledgment JWZ and QZZ contributed equally to this work. This work was financially supported by the Foundation for the Author of National Excellent Doctoral Dissertation of PR China (201035), the Program for New Century Excellent Talents in University (NCET-10-0397). ZLW thanks the support of the Knowledge Please cite this article as: J. Zhong, et al., Finger typing driven tribo LEDs, Nano Energy (2012), http://dx.doi.org/10.1016/j.nanoen.2012. Innovation Program of the Chinese Academy of Sciences (Grant no. KJCX2-YW-M13). The authors would like to thank professor C. X. Wang from Sun Yat-sen University for his support. Appendix A. Supporting information Supplementary data associated with this article can be found in the online version at http://dx.doi.org/10.1016/j.nanoen. 2012.11.015. References [1] J.A. Rogers, Y.G. Huang, A. Curvy, Proceedings of the National Academy of Sciences 106 (2009) 10875. [2] D.H. Kim, N. Lu, R. Ma, Y.S. Kim, R.H. Kim, S. Wang, J. Wu, S.M. Won, H. Tao, A. Islam, et al., Science 333 (2011) 838. [3] Z.L. Wang, J.H. Song, Science 312 (2006) 242. [4] B.Z. Tian, X.L. Zheng, T.J. Kempa, Y. Fang, N.F. Yu, G.H. Yu, J.L. Huang, C.M. Lieber, Nature 449 (2007) 885. [5] D. Kraemer, B. Poudel, H.P. Feng, J.C. Caylor, B. Yu, X. Yan, Y. Ma, X.W. Wang, D.Z. Wang, A. 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Lang, IEEE Transcations on Circuits and Systems I: Regular Papers 53 (2006) 288. [27] P.D. Mitcheson, P. Miao, B.H. Stark, E.M. Yeatman, A.S. Holmes, T.C. Green, Actuators A 115 (2004) 523. [28] S.P. Beeby, M.J. Tudor, N.M. White, Measurement Science and Technology 17 (2006) 175. electric nanogenerator and its use for instantaneously lighting up 11.015 dx.doi.org/10.1016/j.nanoen.2012.11.015 dx.doi.org/10.1016/j.nanoen.2012.11.015 dx.doi.org/10.1016/j.nanoen.2012.11.015 dx.doi.org/10.1016/j.nanoen.2012.11.015 dx.doi.org/10.1016/j.nanoen.2012.11.015 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 55 57 59 61 63 7Finger typing driven triboelectric nanogenerator Junwen Zhong received his B.S. degree in Applied Chemistry from Huazhong Univer- sity of Science and Technology (HUST), China in 2011. He is a Ph.D. candidate in Wuhan National Laboratory for Optoelectro- nics (WNLO) and School of Optical and Electronic Information at HUST. His research interests is energy harvesting for self- powered system. 65 67 69 71 73 Qize Zhong received his B.S. degree in Optoelectronic Information from Huazhong University of Science and Technology(- HUST), PR China in Jun, 2011. He is a Ph.D. candidate in Wuhan National Labora- tory for Optoelectronics (WNLO) and School of Optical and Electronic Information at HUST. His research interests include flexible electronics. 75 77 79 81 83 Fengru Fan received his B.S. degree in Chemistry from Xiamen University, China in 2006. He is a Ph.D. candidate in College of Chemistry and Chemical Engineering at Xiamen University. From 2008 to 2011, he studied as a visiting student in Zhong Lin Wang’s group at Georgia Institute of Tech- nology. His research interests include nano- generators and self-powered nanosystem, preparation and applications of metal– 85 87 89 91 93 95 semiconductor hybrid devices, synthesis and characterization of novel nanostructures with functional materials. Yan Zhang received his B. S. degree (1995) and Ph.D degree in Theoretical Physics (2004) from Lanzhou University. Then, he worked as a lecturer and associate Professor (2007) of Institute of Theoretical Physics in Lanzhou University. In 2009 he worked as research scientist in the group of Professor Zhong Lin Wang at Georgia Institute of Technology. His main research interest and activities are: self-powered nano/micro sys- 97 99 101 103 105 107 tem, theoretical calculation of piezotronic, dynamics of time-delay systems and complex networks. Sihong Wang received his B. S. degree in Materials Science and Engineering from Tsin- ghua University, China in 2009. He is a Ph.D. candidate in Materials Science and Engineering at Georgia Institute of Technology. His main research interest is synthesis of ZnO nanowires and fabrication of nanodevices. 109 Please cite this article as: J. Zhong, et al., Finger typing driven tribo LEDs, Nano Energy (2012), http://dx.doi.org/10.1016/j.nanoen.2012. Bin Hu received his Ph.D. in materials science at Wuhan University of Technology in 2011. From 2009–2011, he was a visiting student in Georgia Institute of Technology He joined in Wuhan National Laboratory for Optoelectro- nics (WNOL) from 2012 as an associate pro- fessor, and his main research interest is the flexible sensors for integrated self-powered nano- and microsystems. Dr. Zhong Lin (ZL) Wang is the Hightower Chair in Materials Science and Engineering, Regents’ Professor, Engineering Distinguished Professor and Director, Center for Nanost- ructure Characterization, at Georgia Tech. Dr. Wang is a foreign member of the Chinese Academy of Sciences fellow of American Physical Society, fellow of AAAS, fellow of Microscopy Society of America, and fellow of Materials Research Society. Dr. Wang has been awarded the MRS Medal in 2011 from Materials Research Society and Burton Medal from Microscopy Society of America. He has made original and innovative contributions to the synthesis, discovery, characteriza- tion, and understanding of fundamental physical properties of oxide nanobelts and nanowires, as well as applications of nanowires in energy sciences, electronics, optoelectronics, and biological science. His discovery and breakthroughs in developing nanogenerators establish the principle and technological road map for harvesting mechanical energy from environment and biological systems for powering a personal electronics. His research on self-powered nanosystems has inspired the worldwide effort in academia and industry for studying energy for micro-nano-systems, which is now a distinct disciplinary in energy research and future sensor networks. He coined and pioneered the field of piezo-tronics and piezo-phototronics by introducing piezo- electric potential gated charge transport process in fabricating new electronic and optoelectronic devices. This breakthrough by redesign CMOS transistor has important applications in smart MEMS/NEMS, nanorobotics, human–electronics interface, and sensors. Dr. Wang’s publications have been cited for over 45,000 times. The H-index of his citations is 102. Details can be found at: http://www.nanoscience. gatech.edu. Jun Zhou received his B.S. degree in Mate- rial Physics (2001) and his Ph.D. in Material Physics and Chemistry (2007) from Sun Yat- Sen University, China. During 2005–2006, he was a visiting student in Georgia Institute of Technology. After he obtaining his Ph.D., He worked in Georgia Institute of Technology as a research scientist. He joined in Wuhan National Laboratory for Optoelectronics (WNOL), Huazhong University of Science and Technology (HUST) as a professor from the end of 2009. His main research interest is flexible energy havesting and storage devices for self-powered micro/nanosensor systems. electric nanogenerator and its use for instantaneously lighting up 11.015 dx.doi.org/10.1016/j.nanoen.2012.11.015 dx.doi.org/10.1016/j.nanoen.2012.11.015 dx.doi.org/10.1016/j.nanoen.2012.11.015 dx.doi.org/10.1016/j.nanoen.2012.11.015 dx.doi.org/10.1016/j.nanoen.2012.11.015 Finger typing driven triboelectric nanogenerator and its use for instantaneously lighting up LEDs Introduction Experimental Fabrication of the TENG Results and discussions Power generation mechanism of TENG The output performance of TENG Powering 50 LEDs in series by TENG directly TENG used in wireless system Conclusions Acknowledgment Supporting information References