Measured Output Voltages of Piezoelectric Devices Depend on the Resistance of Voltmeter

© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 5320 wileyonlinelibrary.com integrating them in devices permits the applications of devices without external power source or battery. Several examples of various materials and device confi gurations appear in the literature. An example of piezoelectric materials that has been constantly studied is ZnO, mostly in nanowire (NW) form. [ 2–4 ] A nanogenerator (NG) based on ZnO NW was an application that utilizes the piezoelectric effect on NWs to harvest energy from the environment for electricity. [ 5 ] A high-level current of ≈500 nA and voltage of ≈10 mV were obtained. In order to solve the problems of the electrical output stability and mechanical robustness in the previous design, Yang et al. [ 6 ] reported a fl exible power generator based on a piezoelectric fi ne wire that was fi rmly attached to the metal electrodes at both ends. Repeating stretching and releasing a single wire with a strain of 0.05–0.1% created an oscillating output voltage of up to ≈50 mV. Xu et al. [ 7 ] reported that a lateral integration of 700 rows of ZnO NWs provided promising capability to charge an AA battery as it yielded an output voltage of 1.26 V. ZnO NWs had also been used to develop a high-output nanogenerator (HONG) on plastic substrates that could generate power to light up a commercial light-emitting diode (LED). [ 8 ] Li et al. [ 9 ] showed the feasibility of harvesting energy from the pulmonary motions and heartbeat of animals. PZT-based NGs have also been investigated as they can generate higher power outputs than other semiconductive Measured Output Voltages of Piezoelectric Devices Depend on the Resistance of Voltmeter