The inset displaysthe measurement of piezoelectric current under various degrees
of bending. Figure 6 reveals that the increase in the output
current is correlated with the bending, for which the result is
consistent with the measurements in Figure 5. The compressive
energy of the sample ZnO nanowires was transferred to
piezoelectric energy. The sample under 2% bending generated
approximately double the current that was generated by the
sample under 1% bending. The former sample generated a
maximum measured current of around 2.5 × 10−9 A under
instantaneous compressive bending, but the compressioninduced
piezoelectric current decreased over time. The bent
sample was clamped in a holder, which did not supply any
physical energy to the sample, but the bent sample still
provided a stable current of approximately 5 × 10−10 A,
suggesting that the current is associated with the flexible
substrate and deformation energy of the substrate under
internal stress. Therefore, the internal stress increased with
deformation, increasing the current.
Figure 7 plots the piezoelectric current of the bent sample
under vibration, which was caused by a rotating cooling fan.