This paper reviews the state-of-the art in vibration energy harvesting for wireless, self-powered microsystems. Vibration-powered generators are typically, although not exclusively, inertial spring and mass systems. The characteristic equations for inertial-based generators are presented, along with the specific damping equations that relate to the three main transduction mechanisms employed to extract energy from the system. These transduction mechanisms are: piezoelectric, electromagnetic and electrostatic. Piezoelectric generators employ active materials that generate a charge when mechanically stressed. A comprehensive review of existing piezoelectric generators is presented, including impact coupled, resonant and human-based devices. Electromagnetic generators employ electromagnetic induction arising from the relative motion between a magnetic flux gradient and a conductor. Electromagnetic generators presented in the literature are reviewed including large scale discrete devices and wafer-scale integrated versions. Electrostatic generators utilize the relative movement between electrically isolated charged capacitor plates to generate energy. The work done against the electrostatic force between the plates provides the harvested energy. Electrostatic-based generators are reviewed under the classifications of in-plane overlap varying, in-plane gap closing and out-of-plane gap closing; the Coulomb force parametric generator and electret-based generators are also covered. The coupling factor of each transduction mechanism is discussed and all the devices presented in the literature are summarized in tables classified by transduction type; conclusions are drawn as to the suitability of the various techniques.

/pdf/energy-harvesting-vibration-sources-for-microsystems-46t885pwdp.pdf

Energy harvesting vibration sources for microsystems applications

The field of power harvesting has experienced significant growth over the past few years due to the ever-increasing desire to produce portable and wireless electronics with extended lifespans. Current portable and wireless devices must be designed to include electrochemical batteries as the power source. The use of batteries can be troublesome due to their limited lifespan, thus necessitating their periodic replacement. In the case of wireless sensors that are to be placed in remote locations, the sensor must be easily accessible or of a disposable nature to allow the device to function over extended periods of time. Energy scavenging devices are designed to capture the ambient energy surrounding the electronics and convert it into usable electrical energy. The concept of power harvesting works towards developing self-powered devices that do not require replaceable power supplies. A number of sources of harvestable ambient energy exist, including waste heat, vibration, electromagnetic waves, wind, flowing water, and solar energy. While each of these sources of energy can be effectively used to power remote sensors, the structural and biological communities have placed an emphasis on scavenging vibrational energy with piezoelectric materials. This article will review recent literature in the field of power harvesting and present the current state of power harvesting in its drive to create completely self-powered devices.

/pdf/a-review-of-power-harvesting-using-piezoelectric-materials-k69swwfj1u.pdf

A review of power harvesting using piezoelectric materials (2003–2006)

Power consumption is forecast by the International Technology Roadmap of Semiconductors (ITRS) to pose long-term technical challenges for the semiconductor industry. The purpose of this paper is threefold: (1) to provide an overview of strategies for powering MEMS via non-regenerative and regenerative power supplies; (2) to review the fundamentals of piezoelectric energy harvesting, along with recent advancements, and (3) to discuss future trends and applications for piezoelectric energy harvesting technology. The paper concludes with a discussion of research needs that are critical for the enhancement of piezoelectric energy harvesting devices.

/pdf/powering-mems-portable-devices-a-review-of-non-regenerative-30r5zxggdp.pdf

Powering MEMS portable devices—a review of non-regenerative and regenerative power supply systems with special emphasis on piezoelectric energy harvesting systems

Piezoelectric materials can be used as a means of transforming ambient vibrations into electrical energy that can then be stored and used to power other devices. With the recent surge of microscale devices, piezoelectric power generation can provide a convenient alternative to traditional power sources used to operate certain types of sensors/actuators, telemetry, and MEMS devices. However, the energy produced by these materials is in many cases far too small to directly power an electrical device. Therefore, much of the research into power harvesting has focused on methods of accumulating the energy until a sufficient amount is present, allowing the intended electronics to be powered. In a recent study by Sodano et al. (2004a) the ability to take the energy generated through the vibration of a piezoelectric material was shown to be capable of recharging a discharged nickel metal hydride battery. In the present study, three types of piezoelectric devices are investigated and experimentally tested to deter...

Comparison of piezoelectric energy harvesting devices for recharging batteries

A microelectromechanical system (MEMS) piezoelectric energy harvesting device, a unimorph PZT cantilever with an integrated Si proof mass, was designed for low vibration frequency and high vibration amplitude environment. Pt/PZT/Pt/Ti/SiO2 multilayered films were deposited on a Si substrate and then the cantilever was patterned and released by inductively coupled plasma reactive ion etching. The fabricated device, with a beam dimension of about 4.800 mm × 0.400 mm × 0.036 mm and an integrated Si mass dimension of about 1.360 mm × 0.940 mm × 0.456 mm produced 160 mVpk, 2.15 μW or 3272 μW cm−3 with an optimal resistive load of 6 kΩ from 2g (g = 9.81 m s−2) acceleration at its resonant frequency of 461.15 Hz. This device was compared with other demonstrated MEMS power generators.

https://iopscience.iop.org/article/10.1088/0960-1317/18/5/055017/pdf

The design, fabrication and evaluation of a MEMS PZT cantilever with an integrated Si proof mass for vibration energy harvesting

The use of piezoelectric materials for power harvesting has attracted significant interest over the past few years. The majority of research on this subject has sought to quantify the amount of energy generated in power harvesting applications, or to develop methods of improving the amount of energy generated. Usually, a monolithic piezoelectric material with a traditional electrode pattern and poled through its thickness is used for power harvesting. However, in recent years several companies and research institutions have begun to develop and market a broad range of piezoelectric composite sensor/actuator packages, each conceived for specific operational advantages and characteristics. Commonly, these devices are employed in control and vibration suppression applications, and their potential for use in power-harvesting systems remains largely unknown. Two frequently implemented design techniques for improving the performance of such actuators are the use of interdigitated electrodes and piezofibers. This paper seeks to experimentally quantify the differences in performance in power-harvesting applications between several of these new actuators and to identify the reasons for their relative performance characteristics. A special focus on the structural and compositional differences between each actuator is incorporated in the discussion of the effectiveness of each actuator as a power-harvesting device.

https://iopscience.iop.org/article/10.1088/0964-1726/15/5/007/pdf

An experimental comparison between several active composite actuators for power generation

The design, fabrication, and testing of a flexible, laminar, anisotropic piezoelectric composite actuator utilizing machined PMN-32%PT single crystal fibers is presented. The device consists of a layer of rectangular single crystal piezoelectric fibers in an epoxy matrix, packaged between interdigitated electrode polyimide films. Quasistatic free-strain measurements of the single crystal device are compared with measurements from geometrically identical specimens incorporating polycrystalline PZT-5A and PZT-5H piezoceramic fibers. Free-strain actuation of the single crystal actuator at low bipolar electric fields (+/- 250 V/mm) is approximately 400% greater than that of the baseline PZT-5A piezoceramic device, and 200% greater than that of the PZT-5H device. Free-strain actuation under high unipolar electric fields (0-4kV/mm) is approximately 200% of the PZT-5A baseline device, and 150% of the PZT-5H alternate piezoceramic device. Performance increases at low field are qualitatively consistent with predicted increases based on scaling the low-field d33 piezoelectric constants of the respective piezoelectric materials. High-field increases are much less than scaled d33 estimates, but appear consistent with high-field freestrain measurements reported for similar bulk single-crystal and piezoceramic compositions. Measurements of single crystal actuator capacitance and coupling coefficient are also provided. These properties were poorly predicted using scaled bulk material dielectric and coupling coefficient data. Rules-of-mixtures calculations of the effective elastic properties of the single crystal device and estimated actuation work energy densities are also presented. Results indicate longitudinal stiffnesses significantly lower (50% less) than either piezoceramic device. This suggests that single-crystal piezocomposite actuators will be best suited to low induced-stress, high strain and deflection applications.

/pdf/anisotropic-laminar-piezocomposite-actuator-incorporating-bg4n2rtmg0.pdf

Anisotropic Laminar Piezocomposite Actuator Incorporating Machined PMN–PT Single-crystal Fibers

The design, fabrication, and testing of a flexible, planar, anisotropic piezoelectric composite actuator utilizing machined PMN-32%PT single crystal fibers is presented. The device consists of a layer of rectangular single crystal piezoelectric fibers in an epoxy matrix, packaged between interdigitated electrode polyimide films. Quasistatic free-strain measurements of the single crystal device are compared with measurements from geometrically identical specimens incorporating polycrystalline PZT-5A and PZT-5H piezoceramic fibers. Free-strain actuation of the single crystal actuator at low bipolar electric fields (+/- 250 V/mm) is approximately 400% greater than that of the baseline PZT-5A piezoceramic device, and 200% greater than that of the PZT-5H device. Free-strain actuation under high unipolar electric fields (0-4kV/mm) is approximately 200% of the PZT-5A baseline device, and 150% of the PZT-5H alternate piezoceramic device. Performance increases at low field are qualitatively consistent with predicted increases based on scaling the low-field d(sub 33) piezoelectric constants of the respective piezoelectric materials. High-field increases are much less than scaled d(sub 33) estimates, but appear consistent with high-field freestrain measurements reported for similar bulk single-crystal and piezoceramic compositions. Measurements of single crystal actuator capacitance and coupling coefficient are also provided. These properties were poorly predicted using scaled bulk material dielectric and coupling coefficient data. Rules-of-mixtures calculations of the effective elastic properties of the single crystal device and estimated actuation work energy densities are also presented. Results indicate longitudinal stiffnesses significantly lower (50% less) than either piezoceramic device. This suggests that single-crystal piezocomposite actuators will be best suited to low induced-stress, high strain and deflection applications.

/pdf/anisotropic-piezocomposite-actuator-incorporating-machined-1tgiz60z8t.pdf

Anisotropic Piezocomposite Actuator Incorporating Machined PMN-PT Single Crystal Fibers

The use of piezoelectric materials for power harvesting has gained significant interest over the past few years. The majority of research on this subject has sought to quantify the amount of energy generated in power harvesting applications, or to develop methods of improving the amount of energy generated. Usually, a monolithic PZT material with a traditional electrode pattern and poled through its thickness is used in power harvesting research projects. In recent years, however, several companies and research institutions have begun to develop and market a broad range of piezoelectric composite sensor/actuator packages, each conceived for specific operational advantages and characteristics. Commonly, these devices are employed in control and vibration suppression applications, and their potential for use in power harvesting systems remains largely unknown. Two frequently implemented design techniques for improving the performance of such actuators are the use of interdigitated electrodes and piezofibers. This paper seeks to experimentally quantify the differences in power harvesting application performance between several of these new actuators and to identify the reasons for their relative performance characteristics. A special focus on the structural and compositional differences between each actuator is incorporated in the discussion of the effectiveness of each actuator as power harvesting devices.

While exhibiting powerful characteristics, monolithic piezoelectric sensors and actuators suffer from many drawbacks due to inherent material properties and implementation issues. As a result of their stiff structure and primary operating principle, monolithic piezoelectric wafers perform poorly in a variety of important engineering applications. Piezoelectric Fiber Composites (PFCs) offer one possible solution to these limitations. Mechanically flexible and functioning on the basis of the d33 effect, these actuators enable and improve many piezoelectric applications. The NASA-Langley Research Center recently developed the Macro-Fiber Composite (MFC) actuator to address several shortcomings in the operational characteristics of competing PFC packages. While the construction of this actuator results in many advantages over comparable PFCs, potential exists for improvement in the design of the MFC. Thus, the single-crystal MFC is proposed. Single-crystal PMN, a specific piezoceramic compound, comprises the piezoceramic fibers of the proposed device, contributing larger piezoelectric coupling, higher bandwidth and higher stiffness to the MFC configuration. Development of this new actuator necessitates extensive characterization of its electromechanical properties. This paper describes the development and computational results of a short-circuit stiffness model that produces the four independent mechanical properties which describe the single-crystal MFC. Modeling results are compared to those of the standard MFC.

Justin M. Lloyd

Papers

An experimental comparison between several active composite actuators for power generation

Anisotropic Laminar Piezocomposite Actuator Incorporating Machined PMN–PT Single-crystal Fibers

Anisotropic Piezocomposite Actuator Incorporating Machined PMN-PT Single Crystal Fibers

An experimental comparison between several active composite actuators for power generation

An analytical model of the mechanical properties of the single-crystal macro-fiber composite actuator