Characterization of the harvesting capabilities of an ionic polymer metal compositedevice

Abstract

Harvesting systems capable of transforming dusty environmental energy into electricalenergy have aroused considerable interest in the last two decades. Several researchworks have focused on the transformation of mechanical environmental vibrationsinto electrical energy. Most of the research activity refers to classic piezoelectricceramic materials, but more recently piezoelectric polymer materials have beenconsidered. In this paper, a novel point of view regarding harvesting systems isproposed: using ionic polymer metal composites (IPMCs) as generating materials.The goal of this paper is the development of a model able to predict the energy harvestingcapabilities of an IPMC material working in air. The model is developed by using the vibrationtransmission theory of an Euler–Bernoulli cantilever IPMC beam. The IPMC is consideredto work in its linear elastic region with a viscous damping contribution ranging from 0.1 to100 Hz. An identification process based on experimental measurements performed on aNafion® 117 membrane is used to estimate the material parameters. The model validation shows agood agreement between simulated and experimental results.The model is used to predict the optimal working region and the optimal geometricalparameters for the maximum power generation capacity of a specific membrane. The modeltakes into account two restrictions. The first is due to the beam theory, whichimposes a maximum ratio of 0.5 between the cantilever width and length. Thesecond restriction is to force the cantilever to oscillate with a specific strain; inthis paper a 0.3% strain is considered. By considering these two assumptionsas constraints on the model, it is seen that IPMC materials could be used aslow-power generators in a low-frequency region. The optimal dimensions for theNafion® 117 membraneare length = 12 cmand width = 6.2 cm, and the electric power generation is 3 nW at a vibrating frequency of7.09 rad s−1. IPMC materials can sustain big yield strains, so by increasing the strain allowed on thematerial the power will increase dramatically, the expected values being up to a fewmicrowatts.