PIEZOELECTRET FOAM-BASED VIBRATION ENERGY HARVESTER FOR LOW- POWER ENERGY GENERATION

摘要

The use of energy harvesting systems to provide power to low-power electronic devices has the potential to create autonomous, self-powered electronics. While research has been performed to study the harvesting of ambient energy through a wide variety of transduction mechanisms, this paper presents the investigation of a novel material for vibration-based energy harvesting. Piezoelectret foam, a polymer-based electret material exhibiting piezoelectric properties, is investigated for low-power energy generation. An overview of the fabrication and operation of piezoelectret foams is first given. Mechanical testing is then performed to evaluate the tensile properties of the material, where anisotropy in the length direction is found along with Young's moduli between 0.5 - 1 GPa and tensile strengths from 35-70 MPa. Dynamic electromechanical characterization is performed in order to measure the piezoelectric d_(33) coefficient of the foam over a wide frequency range. The d_(33) coefficient is found to be relatively constant at 35 pC/N from 5 Hz - 1 kHz. Lastly, energy harvesting tests are performed to evaluate the ability of piezoelectric foam to harvest vibration energy. Frequency response measurements of foam samples excited along the length direction confirm the anisotropic behavior of the material. Harmonic excitation of a pre-tensioned 15.2 cm x 15.2 cm sample at a frequency of 60 Hz and displacement of ± 73 μrn yields an average power of 5.8 μW delivered to a 1 mF storage capacitor through a simple diode bridge rectifier. The capacitor is charged to 4.67 V in 30 minutes, proving the ability of piezoelectret foam to supply power to low-power electronics.