## 3 Results and Discussion
In order to take advantage of a nanophranched structure for potential applications in energy-harvesting devices, its electrical behavior has to be studied in detail to clarify the interactions  
Figure 3: Scanning electron microscopy (SEM) image of the surface morphology of nanophranched ZnO grown on a PEDOT:PSS-coated flexible substrate of PET. Figure 2: X-ray diffraction (XRD) pattern of nanophranched zinc oxide (ZnO) grown on poly(3,4-ethylenedioxythiophene) doped with a polystyrene sulfonate (PEDOT:PSS)-coated flexible substrate of polyethylene teerephthalalate (PET). between the dipole formations and the nanobranches. For this purpose, the permittivity (\(\varepsilon_{r}\)) and the dielectric losses (tan \(\delta\)) were measured at different frequencies (_f_) and temperatures (_T_), as well as at static mechanical load (continuous bended position). The device with nanobranched ZnO showed significantly enhanced relative permittivity compared with dense ZnO and ZnO composites prepared for improving the piezoelectric response [31]. Figure 4a shows that all curves exhibit a similar trend of gradual decrease along with the frequency, with a more significant difference in the values at the negative temperature of \(-10\)\({}^{\circ}\)C. Figure 4b shows that in the frequency range of 20 Hz-20 kHz, little difference can be observed in the curves measured at different temperatures. This may be because all of the nanobranches are similar lengths. This can be confirmed from the SEM image shown previously, where not much difference can be observed between the separate nanoformations. Dielectric losses indicate that a decrement with almost one order of magnitude can be seen in the lower frequency region from a few Hz up to 10 kHz, except for the negative temperature (\(-10\)\({}^{\circ}\)C), where first there is a small increment in the lowest frequency range. All curves follow a similar trend for frequencies higher than 10 kHz. The dielectric losses increase with the temperature (and with the frequency). The higher values at the lower frequency region are related to the electric energy converted into heat loss when the electric field is applied, probably due to impossibility of the dipoles to move fluently among the branched media when no stress (displacement) is applied. The higher values of the dielectric losses at frequencies higher than 30 kHz occurred because of the low dipoles mobility, which prevented any following of the fast changes of the stimulus polarity. The relative permittivity decreased sharply up to 200 Hz, and after that slowed down. This is due to the dipoles' low mobility; because they do not have much time to polarize the media at higher frequencies, weak dependence of the permittivity on the frequencies was observed. The higher permittivity of the nanobranched ZnO (\(\varepsilon_{r}\)\(\sim\)15) compared with the typical values known (\(\varepsilon_{r}\)\(\sim\)9) is probably due to high branch interfacial polarization, which causes an accumulation of charges at the interfaces between each side dendrite and the main core. The dielectric permittivity increased with the temperature increase, too. This can be ascribed to improving the crystallinity, which leads to stronger interfacial polarization. The results from the relative permittivity and dielectric losses measurements of the bended piezoelectric microgenerator samples are shown in Figure 5a,b. They indicate that the bended sample shows a lower permittivity than the case before mechanical loading. This can be ascribed to the dipoles' displacement, and the decrease of the distance between them after deformation [32]. This effect is enhanced by the non-centrosymmetric microstructure of the ZnO due to additional polarization induced by the strain gradient across the sample length (the mechanical loading is different at the maximum curvature and at the attachment points of the samples to the measurement setup).