Flexible piezoelectric nanogenerators based on PVDF-TrFE nanofibers Linda Serairi, Long Gu, Yong Qin, Yingxian Lu, Philippe Basset and Yamin Leprince-Wang Eur. Phys. J. Appl. Phys., 80 3 (2017) 30901 Published online: 23 January 2018 DOI: 10.1051/epjap/2017170288