with energy conversion efficiency higher than the PVDF
thin-film based nanogenerators. The open-circuit voltage
and short-circuit current of this nanogenerator are 5–30mV
and 0.5–3 nA, respectively. In order to increase the output,
they have fabricated 500 parallel nanofibers and connected
them with comb-shape electrodes on flexible substrate to
amplify the current outputs [59]. The peak current was
increased to 35 nA with 0.2mV in peak voltage. Zhao and
co-authors have demonstrated a hybrid LING that consisted
of the piezoelectric PVDF nanofibers fabricated by farfield
electrospinning process [14]. The PVDF nanofibers
were patterned into lateral-aligned arrays on the substrate
and were poled with high field (200 kV/cm) for 15min.
The output voltage and current can be increased from
15 to 20mV and 0.2 to 0.3 nA by increasing the strain
rate of the device, respectively. A detailed review about
the nanofiber-based LINGs until 2012 was demonstrated
by Chang et al. [46]. Moreover, poly(vinylidenefluoride-cotrifluoroethylene)
nanofibers have also been employed for
high-performance flexible piezoelectric nanogenerators [60,
61]. These devices can also be used for mechanical energy
harvesting and ultra-highly sensitive sensing of pressure.
Zeng et al. have combined theNaNbO3,PVDF, and the elastic
conducting knitted fabric nanofibers to obtain all fiber based
nanogenerators, which could generate output voltage of 3.4V
and current of 4.4