Flexoelectric energy harvesters utilizing controllably wrinkled micro-dielectric film

Self-powered electronic devices require energy harvesting systems to support their energy needs, but their energy harvesting efficiency seems still insufficient. In this paper, a flexoelectric energy harvester based on controllable wrinkling mechanism is theoretically proposed to enhance the energy harvesting efficiency. The dielectric film, partly bonded to a pre-stretched substrate, wrinkles after release to achieve controllable wavy shapes. A harmonic cyclic post-stretch is employed to stimulate the generation of electric charges. Meanwhile, an electrode-regrouping technique is resorted to optimize the energy harvesting efficiency. Formulation toward this problem includes both the flexoelectricity and piezoelectricity of dielectrics. Theoretical prediction indicates that electrode-regrouping technique can effectively act to relieve neutralization of the charges induced mainly by flexoelectricity and thus improve the energy harvesting efficiency of FEHs. A larger loading frequency and a lower resistance are preferred to optimize the effective power. The power density of the present FEHs is at least 1 orders of magnitude higher than that of vibrational FEHs under micro-scale. Meanwhile, with the scale shrinking below 100 nm, the energy density of the present FEHs may exceed 104W=m(3) which is generally 2-4 orders of magnitude higher than that of most vibrational energy harvesters (including electrostatic, electromagnetic, piezoelectric types). (C) 2021 Elsevier Ltd. All rights reserved.