UV-Cured Composite Films Containing ZnO Nanostructures: Effect of Filler Shape on Piezoelectric Response

In this work, a facile aqueous sol-gel approach was exploited for synthesizing different ZnO nanostructures; these latter were employed at 4 wt% loading in a UV-curable acrylic system. The piezoelectric behavior of the resulting UV-cured nanocomposite films (NCFs) at resonance and at low frequency (150 Hz, typical value of interest in energy harvesting applications) was thoroughly investigated and correlated to the structure and morphology of the utilized ZnO nanostructures. For this purpose, the NCFs were used as active material into cantilever-shaped energy harvesters obtained through standard microfabrication technology. Interesting piezoelectric behavior was found for all the prepared UV-cured nanostructured films; the piezoelectric response of the different nano-fillers was compared in terms of RMS voltage measured as a function of the applied waveform and normalized to the maximum acceleration applied to the cantilever devices. The obtained results confirmed the promising energy harvesting capability of such ZnO nanostructured films. In particular, flower-like structures showed the best piezoelectric performance both at resonance and 150 Hz, gaining a maximum normalized RMS of 0.914 mV and a maximum peak-peak voltage of about 16.0 mVp-p corresponding to the application of 5.79 g acceleration.