Effect of auxetic structures parameters variation on PVDF-based piezoelectric energy harvesters

This work deals with enhancing piezoelectric energy harvesting by incorporating different auxetic structures and varying geometrical parameters. A bimorph consisting of polyvinylidene fluoride as a piezoelectric layer and brass auxetic substrate (re-entrant, s-shape, and elliptical holes) are considered for analysis. A finite element method-based simulation is performed to find the best auxetic systems that provide higher power output. The environmental vibration is taken for energy harvesting; thus, the first resonance frequency is below 100 Hz. The maximum power of ∼0.52, ∼0.67, and ∼0.79 mW is estimated for piezoelectric energy harvesters (PEH’s) re-entrant, s-shape, and elliptical holes. The auxetic re-entrant, s-shape, and elliptical substrate-based PEHs show 200%, 300%, and 333% more power than the solid substrate (conventional design). However, the elliptical-based auxetic structure obtains a maximum power density of 0.004 66 mW/mm3. The stresses in all structures are within the permissible limit; hence, any design can be used for practical applications. All three auxetics have comparable geometrical dimensions and the same material is used; thus, auxetic behavior is independent of the material employed and depends on the structure’s shape. The estimated power is higher than that reported in the literature.