Wide-bandwidth piezoelectric energy harvester integrated with parylene-C beam structures

• A wide-bandwidth MEMS piezoelectric energy harvester by the Duffing effect.
• Parylene-C was employed as the structure material to reduce the resonance frequency.
• The load–deflection relationship for trapezoid doubly-clamped beams was formulated.
• At 615 Hz, with a maximum open-circuit voltage 368 mV, the power achieves to 0.28 μW.
• A wide operational frequencies range is obtained (from 200 Hz to 600 Hz).

This work presents a wide-bandwidth MEMS energy harvester which converts the energy from ambient vibration into the electrical energy using piezoelectric effect. The proposed device consists of an inertia silicon proof-mass with four parylene-C beam structures, and a piezoelectric PVDF layer. In order to achieve wide-bandwidth harvesting, the design of doubly-clamped beams for inducing tensile stretching strain is adopted. The parylene-C beam structures are fabricated by simple RIE etching method, and the silicon proof-mass is made by isotropic wet etching technique. The piezoelectric film is bonded with the beam structure using parylene-C deposition. The measured frequency responses of the resonance structure show a broad frequency range with relatively large oscillation amplitude. When excited at an acceleration of 0.5 g, the energy harvester achieves to a maximum open-circuit voltage of 368 mV. The maximum output power is 0.288 μW.

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