Piezoelectric energy harvesters have been extensively researched for use with wireless sensors or low power consumption electronic devices. Most of the piezoelectric energy harvesters cannot generate enough power for potential applications. In this study, we explore the parameters, including gap and proof mass, that can affect the damping of the cantilever to optimize the design of the energy harvester. A finite analysis is conducted using COMSOL Multiphysics software. Usually, this type of simulation is performed using the loss factor. However, it is known that results from the loss factor produce models that do not fit the experimental data well. In fact, the result of output voltage using the loss factor is 50% higher than the real value, which is due to ignoring the adverse effect of a superimposing mechanical damping of different constituent materials. In order to build a true model, Rayleigh damping coefficients are measured to use in a simulation. This resulted in a closer fit of modeling and experimental data, and a 5 times better output voltage from the optimized energy harvester compared with using the smallest gap and mass.

Energy harvesting using the piezoelectric material in the development of compact vibration energy harvesters can be used as a backup power source for wireless sensors or to fully replace the use of fossil-resource-wasting batteries and accumulators to power a device or sensor. Generally, the coefficient is used as the metric for evaluating the property in materials. Recent research reports that accurate measurement and calculation of the coefficient in materials, especially in polymers, can be challenging for various reasons. From the reviewed references, different methods, including the quasi-static, dynamic, interferometric, and acoustic methods, are discussed and compared based on the direct and indirect effect, accuracy, repeatability, frequency range, and so on. A development of an ultrasound piezoelectric transducer is conducted to estimate $d_{33}$ coefficient with a reference value. The purpose of the method was mainly to measure the values of piezoelectric material in order to measure the efficiency of the poling process in piezoelectric materials. The test setup described in this study allowed for the effective measurement of the $d_{33}$ factor of piezoelectric materials using a 1.4 MHz PZT ultrasonic piezoelectric transducer. The arrangement of the components, including the use of organic glass, copper, and aluminum electrodes, ensured accurate and reliable measurements. This setup can be valuable for various applications requiring the characterization of piezoelectric materials and for understanding their behavior under specific conditions. The advantages and challenges in this method are discussed and compared with existing works.

Piezoelectric energy harvesters operate by converting mechanical vibrations or strains into electrical energy. From recent research, it is understood that the choice of coating material for piezoelectric energy harvesters is a critical consideration that impacts the device’s performance, durability, and compatibility with the intended application. Selecting the right coating material involves balancing the electrical, mechanical, and environmental requirements to optimize energy conversion and reliability. There are methods like the thermocycling process that can provide an accelerated ageing of the energy harvester in order to conduct a reliability assessment. The thermocycling process was carried out for 450 h on six samples of piezoelectric cantilever-type energy harvesters made of copper–nickel- and aluminum-coated PVDF (Polyvinylidene fluoride) piezoelectric material. The effect of aluminum and copper–nickel coating on PVDF piezoelectric material before and after the aging process was studied. The numerical results of the generated output voltage, surface resistance, and capacitance values measured before and after the accelerated aging process are presented in this study. This work also discusses the structure of the developed energy harvester, thermocycling experiment setup, and methodology of conducting the ageing process. It aims to provide a conclusion on the suitability of the PVDF metal coating material, the type of conductive adhesive to be used in order to seal the PVDF material to the harvester core, improvements in the structural design and selection of materials to reduce mechanical fatigue and ensure even stress distribution, and minimizing points of stress concentration, to help mitigate piezoelectric material delamination risks.

In poly (vinylidene fluoride) (PVDF) polymer films, α-phase usually dominates but only β-phase exhibits the strongest Ferro- and piezoelectric properties. To explore the influence of different conditions on the piezoelectric property of PVDF, in this paper, parameters dependence of dielectric properties of piezoelectric material poly (vinylidene fluoride) (PVDF) were quantitatively analysed by a piezoelectric resonance method. The dielectric coefficient d33 was used to evaluate the piezoelectricity of PVDF. The results show that poling time has a limited effect on d33, which means there will be no further change in d33 after poling enough time. For poling voltage, the d33 increased with voltage until the breakdown of PVDF material. There’s a linear relationship between d33 and poling voltage, as long as poling time is enough. Poling temperature also has an effect on d33, which can help increase d33. But there will be a reduction in d33 measuring after 24 hours. It also needs to be mentioned that the decrease rate is different while poling in different temperatures.

Energy harvesting technologies and material science has made it possible to tap into the abundant amount of surrounding vibrational energy to efficiently convert it into useable energy providing power to portable electronics and IoT devices. Recent investigations show that the piezoelectric effect is created in cellular polymers called ferroelectrets. These cellular-compliant polymers with polarized pores have a piezoelectric response to generate electrical energy when subjected to mechanical strain or surrounding vibration. It is found that there is a significant difference between ferroelectret polarized cellular polypropylene foam and traditional piezoelectric polymers such as polyvinylidene fluoride (PVDF). The former has approximately ten times higher piezoelectric coefficient than the latter. This means that with an acceleration of 9.81 $\mathrm{m}/{\mathrm{s}}^2$ force on this material, ferroelectrets generate up to 39 (µW/g/${\mathrm{m}\mathrm{m}}^3$) power output. Designing a polypropylene-based piezoelectric energy harvester based on the d33 mode of vibration can be challenging due to several factors, as it requires balancing multiple factors such as mechanical stability, piezoelectric response, circuit topology, electrode size, spacing, placement relative to the piezoelectric material, and so on. This paper proposes the preliminary experimental investigation of ferroelectret cellular polypropylene foam in harvesting performance. Suggestions of different approaches for the structural design of energy harvesters are provided. The vibration-dependent response and generated output are examined concerning pulse or sinusoidal input excitation. The voltage generated for both excitations is compared and suggestions are provided regarding the suitable kind of excitation for the chosen ferroelectret material. Finally, conclusions and prospects for ferroelectret materials used in energy-harvesting applications are given.

This work presents an energy harvesting system by leveraging the open power of vibration. The object of this paper is a multilayer piezoelectric vibrational energy harvesting device consisting of relatively flexible cantilever beam covered with PVDF, which is enveloped with electrodes enabling to collect charge developed across deformed piezoelectric material. This cantilever beam is supported by a rigid mechanical support (steel substrate), incorporated into the harvester with the aim to widen its operational frequency range and prolong lifetime. The designed harvester successfully generates an average power of 9.2 μW/g/mm³ with a resonant frequency of 43Hz, generating at least 15 V RMS voltage and 495 μW power for acceleration 1g. Whereas the commercial piezo sensors generate power of 10 nW/g/mm³. The method of fabrication of the proposed energy harvester is discussed. The performance of proposed energy harvester and commercially available piezo sensor is compared and discussed in this work.