Electret transducer for vibration-based energy harvesting

Hillenbrand, J.; Pondrom, Perceval; Sessler, G. M.

doi:10.1063/1.4919875

Cited by 56 publications

(41 citation statements)

References 23 publications

(16 reference statements)

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“…The formation of PP films involves a process in which biaxial stretching results in lens-like voids in the material due to initially compound small particles such as minerals (which act as nuclei for void creation) prior to corona discharging [12,13]. There has been growing interest [11,[14][15][16] in the use of PP films for energy harvesting as an alternative to PVDF [8][9][10] and other soft materials such as dielectric elastomers [17,18] and ionic polymer-metal composites [19,20].…”

Section: Introductionmentioning

confidence: 99%

Figure of merit comparison of PP-based electret and PVDF-based piezoelectric polymer energy harvesters

et al. 2016

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The harvesting of mechanical strain and kinetic energy has received great attention over the past two decades in order to power wireless electronic components such as those used in passive and active monitoring applications. Piezoelectric ceramics, such as PZT (lead zirconate titanate), constitute the most commonly used electromechanical interface in vibration energy harvesters. However, there are applications in which piezoelectric ceramics cannot be used due to their low allowable curvature and brittle nature. Soft polymer PVDF (polyvinylidene fluoride) is arguably the most popular non-ceramic soft piezoelectric energy harvester material for such scenarios. Another type of polymer that has received less attention is PP (polypropylene) for electret-based energy harvesting using the thickness mode (33-mode). This work presents figure of merit comparison of PP versus PVDF for off-resonant energy harvesting in thickness mode operation, revealing substantial advantage of PP over PVDF. For thicknessmode energy harvesting scenarios (e.g. dynamic compression) at reasonable ambient vibration frequencies, the figure of merit for the maximum power output is proportional to the square of the effective piezoelectric strain constant divided by the effective permittivity constant. Under optimal conditions and for the same volume, it is shown that PP can generate more than two orders of magnitude larger electrical power as compared to PVDF due to the larger effective piezoelectric strain constant and lower permittivity of the former.

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Section: Introductionmentioning

confidence: 99%

Figure of merit comparison of PP-based electret and PVDF-based piezoelectric polymer energy harvesters

et al. 2016

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“…[7,8] Ferroelectret polymers with an average pore diameter of 0.9 µm or a pore height of 4.5 µm and pore width of 1.55 µm were also demonstrated to produce 44.9 nW [9] and 4.35 mW [10] for energy harvesting applications. Therefore, ferroelectrets have gained much interest in low-level mechanical energy harvesting [11] and sensing [4] based on their relatively high piezoelectric coefficient and low permittivity. 3 To create ferroelectret materials with a high electro-mechanical response, a cellular geometry or lens-shaped pore structure is desirable with pores that are elongated in the lateral extension; this can be typically > 10 μm long and only a few μm in height [12,13].…”

Section: Introductionmentioning

confidence: 99%

Ice-templated poly(vinylidene fluoride) ferroelectrets

2019

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Ferroelectrets are piezoelectrically-active polymer foams that can convert externally applied loads into electric charge. Existing processing routes used to create pores of the desired geometry and degree of alignment appropriate for ferroelectrets are based on complex mechanical stretching and chemical dissolution steps. As a simple, cost effective and environmentally friendly approach, freeze casting is able to produce aligned pores with almost all types of the materials, including polymers. In this work, we present the first demonstration of freeze casting to create polymeric ferroelectrets. The pore morphology, phase analysis, relative permittivity and direct piezoelectric charge coefficient (d33) of porous poly(vinylidene fluoride (PVDF) ferroelectrets with porosity volume fractions ranging from 24% to 78% were analysed. The long-range alignment of pore channels produced during directional freezing was shown to be beneficial in forming a highly polarised structure after breakdown of air in the pore channels via corona poling. This new method opens a way to create tailored pores and voids in ferroelectret materials for transducer applications related to sensors and vibration energy harvesting.

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“…21 Among them, electrostatic transducers using electrets (a dielectric material that has a quasi-permanent electric charge or dipole polarization) are increasingly studied with the progress of MEMS technology and are believed to offer a viable solution to battery replacements for microelectronic devices such as autonomous wireless sensors. [22][23][24][25][26] Electret-based electrostatic transducers are variable-capacitor structures that use electrets with quasipermanently implanted charges to generate electric current in response to a relative motion between the electrodes, thus directly convert vibrational energy into electricity. They possess four main advantages if utilized for thermoacoustic power generation.…”

Section: Introductionmentioning

confidence: 99%

An electret‐based thermoacoustic‐electrostatic power generator

et al. 2019

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Summary This study reports a new concept for power generation from thermal energy, which integrates a thermoacoustic engine (TAE) with a contact‐free electret‐based electrostatic transducer. The TAE converts thermal energy into high‐intensity acoustic energy, while the electret‐based electrostatic transducer converts the generated acoustic energy into electricity. The experiments demonstrate the feasibility and potential of the proposed electret‐based thermoacoustic‐electrostatic power generator (TAEPG). The dynamic response of the electrostatic transducer and energy conversion inside the TAE are further investigated using a lumped element model and a frequency‐domain reduced‐order network model. Good agreement is achieved between experimental measurements and theoretical predictions. Furthermore, a parametric study is performed to study the effect of key parameters including the external heating power, air gap, and resistive load on the performance of the TAEPG. Results show that an open‐circuit voltage amplitude of 4.7 V is produced at a closed‐end pressure amplitude of 480 Pa in the experiment, and it is estimated that 25.2% of the acoustic power generated by the TAE has been extracted by the electret‐based electrostatic transducer. In this case, the maximum electric power output is measured to be 2.91 μW at a resistive load of around 2.2 MΩ. By increasing the external heating power, the TAEPG can produce a maximum voltage amplitude of 8 V. This work shows that the proposed concept has great potential for developing miniature heat‐driven power generators.

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Electret transducer for vibration-based energy harvesting

Abstract: Inducing bistability with local electret technology in a microcantilever based non-linear vibration energy harvester

Cited by 56 publications

References 23 publications

Figure of merit comparison of PP-based electret and PVDF-based piezoelectric polymer energy harvesters

Figure of merit comparison of PP-based electret and PVDF-based piezoelectric polymer energy harvesters

Ice-templated poly(vinylidene fluoride) ferroelectrets

An electret‐based thermoacoustic‐electrostatic power generator

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