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.

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Energy harvesting vibration sources for microsystems applications

Energy harvesting generators are attractive as inexhaustible replacements for batteries in low-power wireless electronic devices and have received increasing research interest in recent years. Ambient motion is one of the main sources of energy for harvesting, and a wide range of motion-powered energy harvesters have been proposed or demonstrated, particularly at the microscale. This paper reviews the principles and state-of-art in motion-driven miniature energy harvesters and discusses trends, suitable applications, and possible future developments.

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Energy Harvesting From Human and Machine Motion for Wireless Electronic Devices

This paper describes the design of miniature generators capable of converting ambient vibration energy into electrical energy for use in powering intelligent sensor systems. Such a device acts as the power supply of a microsystem which can be used in inaccessible areas where wires can not be practically attached to provide power or transmit sensor data. Two prototypes of miniature generator are described and experimental results presented. Prototype A is based around two magnets coupled to a coil attached to a cantilever; prototype B is based around four magnets. For prototype A, experimental results are given for its resonant frequency and its open circuit and loaded output as a function of vibration amplitude. For prototype B, experimental results are given for the generator's Q factor in air and vacuum, its output voltage as a function of vibration amplitude as well as its magnetic field strength. This generator has been tested on a car engine and shown to produce a peak power of 3.9 mW with an average power of 157 micro watts.

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An electromagnetic, vibration-powered generator for intelligent sensor systems

This paper reviews the development of energy harvesting for low-power embedded structural health monitoring (SHM) sensing systems. A statistical pattern recognition paradigm for SHM is first presented and the concept of energy harvesting for embedded sensing systems is addressed with respect to the data acquisition portion of this paradigm. Next, various existing and emerging sensing modalities used for SHM and their respective power requirements are summarized followed by a discussion of SHM sensor network paradigms, power requirements for these networks, and power optimization strategies. Various approaches to energy harvesting and energy storage are discussed and limitations associated with the current technology are addressed. The paper concludes by defining some future research directions that are aimed at transitioning the concept of energy harvesting for embedded SHM sensing systems from laboratory research to field-deployed engineering prototypes. Finally, it is noted that many of the technologies discussed herein are applicable to powering any type of low-power embedded sensing system regardless of the application.

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Energy Harvesting for Structural Health Monitoring Sensor Networks

As the wireless sensor networks (WSNs) technology has great advancement, small and smart WSN systems now can be used for more complicated and challenging applications. WSNs investigation has primarily believed the use of a convenient and inadequate energy source for empowering the sensors. A sensor becomes useless in the absence of energy and becomes unable to contribute to the utility of the network as a group. Therefore, extensive efforts have been used in finding energy-efficient networking protocols for increasing the life span of WSNs. However, there are promising WSN applications where the sensors are obligatory to work for a long time after their deployments. In these cases, batteries are tough or impractical to replace/recharge. Although, a little amount of power is required for these applications, the useable lifetime of WSNs is decreased by the gradual degradation of the batteries. With the motivation of raising the usable WSNs around us and to value a number of economic and environmental limitations, researchers are looking for new green and theoretically unlimited energy sources. Harvesting of energy from the ambient energy is the basement of these new sources. Energy harvesting devices efficiently and effectively capture, accumulate, store, condition, and manage this energy and supply it in a form that can be used to empower WSNs. This harvested energy can be an alternative energy source for adding-on a principal power source and thus increase the consistency of the whole WSN by preventing the disruption of power. A great deal of research has been reviewed and specific ranges of applications have been found. Though there are challenges to overcome, different researchers have taken different approaches to solve those. In this review, we have emphasized on different scopes, challenges, ideas and actions of energy harvesting for WSNs.

Energizing Wireless Sensor Networks by Energy Harvesting Systems: Scopes, Challenges and Approaches

This paper presents the design, analysis, and experimental results of a vibration-induced power generator with total volume of -1 cm3 that uses laser-micromachined springs as resonating structures. The goal of our research is to create a minimally sized electric power generator capable of producing enough voltage to drive low-power IC circuit systems or micro sensors for robotic and automation applications where mechanical vibrations are present. Potential applications for the generator may also include mobile phone and heart-pacers where human motions can be used as a source of mechanical energy. Thus far, we have produced a generator capable of producing 2V DC with 64Hz input frequency with <200pm input vibration amplitude.

A Micromachined Vibration-Induced Power Generator For Low Power Sensors Of Robotic Systems

This paper presents the preliminary design and experimental results of a standard AA size vibration-induced micro energy transducer which is integrated with a power-management circuit. The transducer is a spring mass system which uses SU-8 molding and MEMS electroplating technologies fabricated copper springs to convert mechanical energy into electrical power by Faraday's law of induction. We have shown that when the MPG is packaged into an AA battery size container along with a power-management circuit that consists of rectifiers and a capacitor, it is capable of producing /spl sim/1.6 V DC when charged for less than 1 min. Potential applications for this micro power generator to serve as a power supply for a wireless temperature sensing system was proved to be possible with input frequencies at about 100 Hz and amplitudes be approximately 250 microns.

AA size micro power conversion cell for wireless applications

This paper presents the design and experimental results of a Micro Power Generator (MPG) which harvests mechanical energy from its environment and converts this energy into useful electrical power. The energy transduction component is mainly a magnet and a resonating spring made using SU-8 molding and MEMS electroplating technologies. We have shown that when the MPG is packaged into an AA battery size container along with a power-management circuit that consists of rectifiers and a capacitor, it is capable of producing ~1.6V DC when charged for less than 1min. Our goal is to realize a MPG to function with low input mechanical frequencies while produce enough power for low-power wireless applications.

Vibration-to-Electrical Power Conversion Using High-Aspect-Ratio MEMS Resonators

This paper presents the design and experimental results of a Micro Power Generator (MPG) which harvests mechanical energy from its environment and converts this energy into useful electrical power. The energy transduction component is mainly a magnet and a resonating spring made using SU-8 molding and MEMS electroplating technologies. We have shown that when the MPG is packaged into an AA battery size container along with a power-management circuit that consists of rectifiers and a capacitor, it is capable of producing ~1.6 V DC when charged for less than 1 min. Our goal is to realize a MPG to function with low input mechanical frequencies while producing enough power for low-power wireless applications.

Self-powered wireless temperature sensing using mems-based aa-size energy transducer

This paper presents the preliminary design and experimental results of a standard AA size vibration-induced micro power generator. The energy transduction unit of this micro power generator is a spring mass system that uses MEMS fabricated copper springs to convert mechanical energy into electrical power by Faraday’s Law of Induction. We have shown that this AA size power cell is capable of producing ~2.5V DC and ~60μW with a 100kΩ loading when charged for about one and a half minutes. Potential applications for this micro power generator to serve as a power supply for a wireless temperature sensing system was proved to be possible with input frequencies at about 79Hz with an amplitude of approximately 250microns.

Gordon M. H. Chan

Papers

A Micromachined Vibration-Induced Power Generator For Low Power Sensors Of Robotic Systems

AA size micro power conversion cell for wireless applications

Vibration-to-Electrical Power Conversion Using High-Aspect-Ratio MEMS Resonators

Self-powered wireless temperature sensing using mems-based aa-size energy transducer

AA Size Power Cell for Wireless Applications Using Micro-Fabricated Resonators