Enhanced Energy Harvesting by Devices with the Metamaterial Substrate

Nowadays, the optimal use of existing energy sources is just as important as the development of new and alternative energy sources. One of the available and renewable energy sources is vibrations. The simplest way to use this energy source is piezoelectric energy harvesters. These harvesters consist of two parts, the piezoelectric element and the substrate to which the piezoelectric element is connected. The geometric structure of the substrate can greatly influence the efficiency of a harvester. In this study, the effect of auxetic substrates on the output voltage of energy harvesters is investigated. For this purpose, two auxetic substrates and one plain substrate are investigated experimentally and numerically. The results show that the use of auxetic substrates 1 and 2 increases the output voltage by 3.45 and 2.18 times, respectively, compared to the plain substrate. A parametric study is conducted to better understand the effect of the geometric parameters of the auxetic unit cell on the energy harvested. Because of the stress concentration and porosity in auxetic substrates and the application of periodic loading, it is necessary to study the growth of cracks and the fatigue life of these structures. The results show that auxetic substrates 1 and 2 have 50 and 72% shorter fatigue lives than the plain substrate, respectively.