Energy Generation Mechanism of Nanorings in Circumferential Oscillations

Abstract

This study focuses on the nanopiezoelectric energy harvesting mechanism of free-floating zinc oxide (ZnO) nanorings. Inner and outer surfaces of a ZnO nanoring are both deposited with an electrode layer that are uniformly and symmetrically segmented into series of couples to serve as distributed energy generators. The generation mechanism of voltage signal is analyzed first, followed by the energy generation analysis. Because of the cancellation of the electric potentials across the nanoring thickness induced by bending strains, the membrane strain is the only contribution to the output voltage and energy generations. The membrane (circumferential) oscillation modes of the nanoring are considered for the analysis of energy generation mechanism. Distributions of the output voltage signal and the generated energy are evaluated with respect to various nanoring modes and design parameters, e.g., nanoring radii and electrode segment sizes. Signal average and cancellation effect reduces the generated signal and energy when the segment size enlarges. The overall energy is also calculated by summing up energies generated from all energy harvesters of the whole nanoring. Analysis suggests that more energy can be generated when the segment size reduces. The energy distributions with respect to nanoring modes provide a design guideline to select proper segmentation and nanoring radius, as well as optimal distributions of electrode patches to achieve highest energy harvesting efficiency for nanoring generators.