51 times. This confirms that the Au-coated silica sphere array played the role of an efficient top electrode on the ZnO NRA-based NGs. Figure 5 Measured results of ZnO NRA-based NG. (a) Measured output current and voltage of the ZnO NRA-based NG with the top electrodes of (i) Au film on PET and (ii) Au-coated silica sphere array on PET under 0.3 kgf of external pushing force. (b) Statistical distributions of the generated output (i) current and (ii) voltage by Gaussian fits. Conclusion We successfully fabricated the efficient top electrode

for ZnO NRA-based NGs by incorporating the Au-coated silica sphere array on the PET substrate. When Au was deposited onto the multilayer of silica spheres, it formed as a highly MK-1775 price rough surface with angulated morphology. By computational simulations for the strain distribution when bending ZnO nanorods, the rough surface of Au-coated silica sphere array could be expected to further increase the bending radius under an external pushing force. For an experimental analysis, the NGs were fabricated with ZnO NRAs on ITO/PET via the ED method and different top electrodes (i.e., Au film on PET and Au-coated silica sphere array on PET). Under an external pushing force of 0.3 kgf, the Au-coated silica sphere array contributed

to the improvement in output current and voltage by about 2.01 and 1.51 times with regular curves. From these results, the Au-coated silica sphere array could be useful for an efficient top electrode in various ZnO nanostructure-based piezoelectric NG applications. Acknowledgements This research was supported by the QNZ cell line Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT and Future Planning (no. 2013–010037). References 1. enough Wang Z, Zhu G, Yang Y, Wang S, Pan C: Progress in nanogenerators for portable electronics. Mater Today 2012, 15:532.CrossRef 2. Choi D, Lee KY, Lee KH, Kim ES, Kim TS, Lee SY, Kim S, Choi J, Kim JM: Piezoelectric touch-sensitive flexible hybrid energy

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