This paper presents a state-of-the-art review on a hot topic in the literature, i.e., vibration based energy harvesting techniques, including theory, modelling methods and the realizations of the piezoelectric, electromagnetic and electrostatic approaches. To minimize the requirement of external power source and maintenance for electric devices such as wireless sensor networks, the energy harvesting technique based on vibrations has been a dynamic field of studying interest over past years. One important limitation of existing energy harvesting techniques is that the power output performance is seriously subject to the resonant frequencies of ambient vibrations, which are often random and broadband. To solve this problem, researchers have concentrated on developing efficient energy harvesters by adopting new materials and optimising the harvesting devices. Particularly, among these approaches, different types of energy harvesters have been designed with consideration of nonlinear characteristics so that the frequency bandwidth for effective energy harvesting of energy harvesters can be broadened. This paper reviews three main and important vibration-to-electricity conversion mechanisms, their design theory or methods and potential applications in the literature. As one of important factors to estimate the power output performance, the energy conversion efficiency of different conversion mechanisms is also summarised. Finally, the challenging issues based on the existing methods and future requirement of energy harvesting are discussed.

A comprehensive review on vibration energy harvesting: Modelling and realization

This paper provides a detailed overview of developments in transducer materials technology relating to their current and future applications in micro-scale devices. Recent advances in piezoelectric, magnetostrictive and shape-memory alloy systems are discussed and emerging transducer materials such as magnetic nanoparticles, expandable micro-spheres and conductive polymers are introduced. Materials properties, transducer mechanisms and end applications are described and the potential for integration of the materials with ancillary systems components is viewed as an essential consideration. The review concludes with a short discussion of structural polymers that are extending the range of micro-fabrication techniques available to designers and production engineers beyond the limitations of silicon fabrication technology.

/pdf/new-materials-for-micro-scale-sensors-and-actuators-an-21qnaonn0l.pdf

New materials for micro-scale sensors and actuators An engineering review

Over the past two decades, several advances have been made in micromachined sensors and actuators. As the field of microelectromechanical systems (MEMS) has advanced, a clear need for the integration of materials other than silicon and its compounds into micromachined transducers has emerged. Piezoelectric materials are high energy density materials that scale very favorably upon miniaturization and that has led to an ever-growing interest in piezoelectric films for MEMS applications. At this time, piezoelectric aluminum-nitride-based film bulk acoustic resonators (FBAR) have already been successfully commercialized. Future innovations and improvements in inertial sensors for navigation, high-frequency crystal oscillators and filters for wireless applications, microactuators for RF applications, chip-scale chemical analysis systems and countless other applications hinge upon the successful miniaturization of components and integration of piezoelectrics and metals into these systems. In this article, a comprehensive review of micromachined piezoelectric transducer technology will be presented. Piezoelectric materials in bulk and thin film forms will be reviewed and fabrication techniques for the integration of these materials for microsensor applications will be presented. Recent advances in various piezoelectric microsensors will be presented through specific examples. This review will conclude with a critical assessment of the future trends and promise of this technology.

https://iopscience.iop.org/article/10.1088/0957-0233/20/9/092001/pdf

Piezoelectric MEMS sensors: state-of-the-art and perspectives

A review of vibration-based MEMS piezoelectric energy harvesters

https://www.repository.cam.ac.uk/bitstream/1810/264501/1/Fu_et_al-2017-Progress_in_Material_Science-VoR.pdf

Advances in piezoelectric thin films for acoustic biosensors, acoustofluidics and lab-on-chip applications

This paper describes fabrication arid characterization results of piezoelectric micromachined ultrasonic transducers (pMUTs) based on 2-/spl mu/m-thick Pb(Zr/sub 0.53/Ti/sub 0.47/O/sub 3/) (PZT) thin films. The applied structures are circular plates held at four bridges, thus partially undamped. A simple analytical model for the fully clamped structure is used as a reference to optimize design parameters such as thickness relations and electrodes, and to provide approximate predictions for coupling coefficients related to previously determined thin film properties. The best coupling coefficient was achieved with a 270-/spl mu/m plate and amounted to k/sup 2/=5.3%. This value compares well with the calculated value based on measured small signal dielectric (/spl epsi/=1050) and piezoelectric (/spl epsi//sub 31,f/=15 Cm/sup -2/) properties of the PZT thin film at 100 kV/cm dc bias. The resonances show relatively large Q-factors, which can be partially explained by the small diameters as compared to the sound wavelength in air and in the test liquid (Fluorinert 77). A transmit-receive experiment with two quasiidentical pMUTs was performed showing significant signal transmission up to a distance of 20 cm in air and 2 cm in the test liquid.

Piezoelectric micromachined ultrasonic transducers based on PZT thin films

Vibration Energy Harvesting with PZT Micro Device

Polycrystalline AlN thin films were deposited by RF reactive magnetron sputtering on Pt(111)/Ti electrode films. The substrates were tilted by an angle ranging from 40° to 70° with respect to the target normal. A low deposition temperature and a high sputter gas pressure were found ideal for tilted growth. The resulting grain tilt angle amounts to about half the substrate tilt angle. For coupling evaluation, 5 GHz solidly mounted resonator structures have been realized. The tilted grain AlN films exhibited a permittivity in the 9.5-10.5 range and loss tangent of 0.3%. Two shear modes as well as the longitudinal mode could be clearly identified. The coupling coefficient k2eff, of the fundamental thickness shear mode (TSO) was found to be about 0.5%, which is compatible with a c-axis tilt of about 6°.

Shear mode coupling and tilted grain growth of AlN thin films in BAW resonators

Shear mode coupling and properties dispersion in 8 GHz range AlN thin film bulk acoustic wave (BAW) resonator

An analytical model based on the clamped plate theory has been used to design the Bimorph pMUT (i.e. frequency). This model gives a good prediction of the experimental frequency of the 5-layers pMUT plate resonance. Our calculation show that central electrodes need to cover 58% and 33% of the membrane surface for a long rectangular and circular membrane respectively to achieve optimal coupling. The electromechanical coupling coefficient (k) and quality factor (Q) were measured as k=4.4% and Q=145 in air for a low frequency transducer (250 kHz). d. The 17 MHz version yielded values of Q=25 and k=3%..

http://ieeexplore.ieee.org/iel5/10674/33678/01602896.pdf

B. Belgacem

Papers

Piezoelectric micromachined ultrasonic transducers based on PZT thin films

Vibration Energy Harvesting with PZT Micro Device

Shear mode coupling and tilted grain growth of AlN thin films in BAW resonators

Shear mode coupling and properties dispersion in 8 GHz range AlN thin film bulk acoustic wave (BAW) resonator

Design, modeling and fabrication of piezoelectric micromachined ultrasonic transducers