Abstract

Energy harvesting devices can convert energy from various ambient sources (that are usually ignored) into electricity to power portable electronic devices and wireless sensor networks. Such devices have stimulated extensive interest in recent years. For the current study, we succeeded in designing and fabricating a new type of energy harvester using high performance unipolar ferroelectrets made from fluorinated ethylene propylene (FEP), consisting of a negatively charged and a noncharged wave-shaped FEP layer. Such materials are resistant to elevated temperatures owing to the thermally stable negative charges in this material. They also exhibit great stretchability due to the symmetric wave-shaped structure. By using a variety of test frequencies, seismic masses, external resistances, and wave-shaped FEP films with different surface potentials, we systematically investigated the energy harvesting performance of these devices. Typically, wave-shaped films with a material thickness of 12.5 μm and a maximum total thickness of the wavy structure (including the air thickness) of about 160 µm were employed. When charged to a surface potential of −500 V and operated with a seismic mass of 3 g fixed on the center of the band shaped unipolar ferroelectret sample, a power of 355 µW for an input acceleration of 1 g (g is the gravity of the Earth) was delivered to the optimal load resistance at the resonance frequency of 22 Hz. The relatively large power generated is due to the sizeable elasticity of the wave-shaped FEP film and the amplification of the force acting on the film in the specifically designed device.

Highlights

  • In the past two decades, accompanied by the development of miniature, low power consumption electronics, a new research field called energy harvesting has arisen and gained increasing attention from both academia and industry.[1,2,3,4,5] Energy harvesting refers to collecting some of the surrounding energy resources, including solar, thermal, and mechanical energy, and converting it into electric energy.[6–9] Numerous advantages of this technology exist, such as durable operation that is inexpensive and eco-friendly

  • When charged to a surface potential of −500 V and operated with a seismic mass of 3 g fixed on the center of the band shaped unipolar ferroelectret sample, a power of 355 μW for an input acceleration of 1 g (g is the gravity of the Earth) was delivered to the optimal load resistance at the resonance frequency of 22 Hz

  • The unipolar ferroelectrets investigated in this study were prepared with two pieces of wave-shaped fluorinated ethylene propylene (FEP) layers and with a symmetric structure, as shown in Fig. 1(a), of which one layer was negatively corona charged to a given surface potential

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Summary

INTRODUCTION

In the past two decades, accompanied by the development of miniature, low power consumption electronics, a new research field called energy harvesting has arisen and gained increasing attention from both academia and industry.[1,2,3,4,5] Energy harvesting refers to collecting some of the surrounding energy resources, including solar, thermal, and mechanical energy, and converting it into electric energy.[6–9] Numerous advantages of this technology exist, such as durable operation that is inexpensive and eco-friendly. In the past two decades, accompanied by the development of miniature, low power consumption electronics, a new research field called energy harvesting has arisen and gained increasing attention from both academia and industry.[1,2,3,4,5] Energy harvesting refers to collecting some of the surrounding energy resources, including solar, thermal, and mechanical energy, and converting it into electric energy.[6–9]. Previous work shows that they have great potential due to their increased thermal stability.[26,27] Their energy harvesting performance was first investigated by using negatively charged polypropylene.[28]. Thermally stable unipolar ferroelectrets were realized with wavy fluorinated ethylene propylene (FEP) films having a negatively charged layer.[29,30] The suggested harvesters incorporating such unipolar ferroelectret films are superior to those with bipolar ferroelectrets since in FEP negative charges are much more thermally stable than positive charges.[31,32] It was found that a relatively large amount of power can be generated with such harvesting devices

WORKING PRINCIPLE OF THE ENERGY HARVESTER
Fabrication process of unipolar ferroelectrets and the energy harvesters
Stretchability of the wave-shaped FEP films
Charge storage performance of negatively charged unipolar FEP films
Humidity sustainability of negatively charged wavy FEP films
Operation and analysis of the unipolar film harvesters
Generated power of the unipolar ferroelectret harvesters and discussion
SUMMARY

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