Cantilever-Based Ferroelectret Energy Harvesting

We present a vibrational energy harvester with fluorinated ethylene propylene (FEP)-ferroelectrets working in d(31) mode. The ferroelectret film consists of two FEP films, fused together to form a parallel tunnel structure with well-defined air gaps. Its dynamic piezoelectric g(31) coefficient is0.7VmN- 1. The energy-harvesting device is an air-spaced cantilever arrangement that was produced by the additive manufacturing technique. The device was tested by exposing it to sinusoidal vibrations with an acceleration a, generated by a shaker. The measurement shows a resonance at about 35Hz and a normalized output power of 320 mu W for a seismic mass of 4.5g at an acceleration of 0.1g (g is the gravity of the earth). This demonstrates a significant improvement of air-spaced vibrational energy harvesting with ferroelectrets and greatly exceeds previous performance data for polymer cantilever devices.