The sample with 2% bending exhibited the largest
piezoelectric current because it exhibited the highest transfer of
compressive energy for vertical force. I, II, and III in Figure 8c
schematically depict three possible types of contact between
ultralong ZnO nanowires and an Pt/ZnO nanowire electrode.
7,10,20 On the basis of previous reports of the piezoelectric
effect, the stretched side of the ZnO nanowires develops a
positive potential (V+) and its compressed side has a negative
potential (V−).