Electronic Supplementary Material (ESI) for Journal of Materials Chemistry A. This journal is © The Royal Society of Chemistry 2018 Supporting Information Layer-by-layer assembled graphene multilayers on multidimensional surfaces for highly durable, scalable, and wearable triboelectric nanogenerators Il Jun Chung,†a Wook Kim,†b Wonjun Jang,a Hyun-Woo Park,c Ahrum Sohn,d Kwun-Bum Chung,c Dong-Wook Kim,d Dukhyun Choi*b and Yong Tae Park*a aDepartment of Mechanical Engineering, Myongji University, 116 Myongji-ro, Cheoin-gu, Yongin, Gyeonggi-do, 17058, Republic of Korea Email: [email protected] bDepartment of Mechanical Engineering, Kyung Hee University, 1732 Deogyeong-daero, Giheung-gu, Yongin, Gyeonggi-do, 17104, Republic of Korea Email: [email protected] cDivision of Physics and Semiconductor Science, Dongguk University, 30, Pildong-ro 1-gil, Jung-gu, Seoul, 04620, Republic of Korea dDepartment of Physics, Ewha Womans University, 52, Ewhayeodae-gil, Seodaemun-gu, Seoul, 03760, Republic of Korea Fig. S1 Power generation mechanism of G-TENGs. a–d) Potential distribution of the G- TENG simulated by the COMSOL multi-physics software. Fig. S2 FE-SEM images of (a) the top surface of a bare (flat) PET substrate, (b) the top surface of an NaOH-etched (undulated) PET substrate, and (c) an NaOH-etched PET substrate tilted about 30 degrees. Fig. S3 (a) Visible light absorbance spectra of the LbL-assembled graphene films (1 to 10 BLs, wavelength = 450-850 nm). (b) Dependence of the light absorbance at 550 nm wavelength of the LbL-assembled graphene films (1 to 10 BLs) on the number of bilayers. (c) Photograph of LbL-assembled graphene films (1 to 10 BLs) assembled on both sides of PET film. Fig. S4 Resistivity (top) and conductivity (bottom) of the LbL-assembled graphene films from 1 to 20 bilayers deposited on bare PET substrates. After 5 BLs, they showed the similar values up to 20 BLs (0.031 Ω cm and 33 S cm-1 at 10 BLs) Fig. S5 Transferred charge density of 3 BL FG-TENG and 3 BL UG-TENG. Fig. S6 Output voltage and current of 3 BL FG-TENG and UG-TENG under the different external loads of 3, 6, and 9 N, respectively. Fig. S7 Output voltage of 3 BL TG-TENG under the different contact materials of dry skin (bare finger, black) and PTFE glove (red), respectively. The other test conditions were contact frequency of 4 Hz, contact load of 6 N, and contact area of 3 cm2 (approximate fingertip size). Fig. S8 Raman spectra of the 3 BL TG-TENG, showing broad D (~1350 cm-1) and G (~1589 cm-1) bands, all of which are characteristic of defective graphene. Supporting Video 1. LEDs on by TG-TENG.