Fabrication and modeling of β-phase PVDF-TrFE based flexible piezoelectric energy harvester

Abstract

There is increased interest in flexible substrate-based piezoelectric energy harvester (PEH) for self-powered wireless sensor nodes, due to their low-cost and environmental friendliness. However, it presents fabrication challenges due to the low-temperature process and formation of a highly polar β-phase of a polymer film on a flexible substrate. In this work, first, we optimize the deposition parameters to grow the polar β-phase of poly vinylidene fluoride trifluoroethylene (PVDF-TrFE) film on Polyethylene terephthalate (PET) substrate. Using optimized PVDF-TrFE film, rectangular shape PEH is fabricated on a flexible Mo/PET substrate and characterized for voltage and power. It is found that the maximum measured power is 6.83 μW with input acceleration of 1.0 g. Further, we develop a novel analytical approach using a mass-spring damper model of PEH to predict the resonance frequency and output power. The fabricated and model results are shown to match well with mechanical and induced electrical damping as fitting parameters. The maximum measured power density from the flexible substrate based PEH is found to be 312.85 μW/cm3. The obtained power density is better than similar reported devices, with the advantage of low-cost material and fabrication. The optimized and low frequency PEHs reported in this work have a high potential for the wireless sensor node applications, such as monitoring of water bodies and plant health monitoring in agriculture, etc.