The investigation of the conversion of vibrational energy into electrical power has become a major field of research. In recent years, bistable energy harvesting devices have attracted significant attention due to some of their unique features. Through a snap-through action, bistable systems transition from one stable state to the other, which could cause large amplitude motion and dramatically increase power generation. Due to their nonlinear characteristics, such devices may be effective across a broad-frequency bandwidth. Consequently, a rapid engagement of research has been undertaken to understand bistable electromechanical dynamics and to utilize the insight for the development of improved designs. This paper reviews, consolidates, and reports on the major efforts and findings documented in the literature. A common analytical framework for bistable electromechanical dynamics is presented, the principal results are provided, the wide variety of bistable energy harvesters are described, and some remaining challenges and proposed solutions are summarized.

https://iopscience.iop.org/article/10.1088/0964-1726/22/2/023001/pdf

A review of the recent research on vibration energy harvesting via bistable systems

http://ieeexplore.ieee.org/iel5/5/31047/01444179.pdf

Fundamentals of acoustics

This review provides a detailed overview of the energy harvesting technologies associated with piezoelectric materials along with the closely related sub-classes of pyroelectrics and ferroelectrics. These properties are, in many cases, present in the same material, providing the intriguing prospect of a material that can harvest energy from multiple sources including vibration, thermal fluctuations and light. Piezoelectric materials are initially discussed in the context of harvesting mechanical energy from vibrations using inertial energy harvesting, which relies on the resistance of a mass to acceleration, and kinematic energy harvesting which directly couples the energy harvester to the relative movement of different parts of a source. Issues related to mode of operation, loss mechanisms and using non-linearity to enhance the operating frequency range are described along with the potential materials that could be employed for harvesting vibrations at elevated temperatures. In addition to inorganic piezoelectric materials, compliant piezoelectric materials are also discussed. Piezoelectric energy harvesting devices are complex multi-physics systems requiring advanced methodologies to maximise their performance. The research effort to develop optimisation methods for complex piezoelectric energy harvesters is then reviewed. The use of ferroelectric or multi-ferroic materials to convert light into chemical or electrical energy is then described in applications where the internal electric field can prevent electron–hole recombination or enhance chemical reactions at the ferroelectric surface. Finally, pyroelectric harvesting generates power from temperature fluctuations and this review covers the modes of pyroelectric harvesting such as simple resistive loading and Olsen cycles. Nano-scale pyroelectric systems and novel micro-electro-mechanical-systems designed to increase the operating frequency are discussed.

/pdf/piezoelectric-and-ferroelectric-materials-and-structures-for-39myuuqvo7.pdf

Piezoelectric and ferroelectric materials and structures for energy harvesting applications

Nonlinear Oscillations: Exact Solutions and their Approximations

High-Performance Piezoelectric Energy Harvesters and Their Applications

This article reports means to significantly enhance the adaptation of static and dynamic properties using magnetorheological elastomers and demonstrates the enhancements experimentally. The tunabil...

https://journals.sagepub.com/doi/pdf/10.1177/1045389X17721037

Adaptive magnetoelastic metamaterials: A new class of magnetorheological elastomers:

We present a new class of reconfigurable origami-based antennas formed by embroidered conductive E-threads. State-of-the-art techniques used to realize origami antennas employ fragile conductive inks and/or copper tape. By contrast, the proposed approach brings forward enhanced robustness and durability as attributed to the inherent strength of the E-threads. To facilitate folding along the creases while also providing the radio frequency (RF) performance close to that of copper, a graded embroidery process is proposed. The grading scheme uses a density of 7 E-threads/mm on the antenna and a reduced density around the creases (as few as 1 E-thread/mm in this study). Proof-of-concept results for an accordion-based dipole antenna tunable from 760 to 1015 MHz show excellent agreement between simulations and measurements for all E-textile prototypes and the copper equivalent. Notably, embroidery density at the creases can be reduced to as low as 1 E-thread/mm without apparent degradation in the RF performance. Overall, the E-textile origami antennas may transform opportunities for reconfigurable antennas to be leveraged in wearable and structural applications.

E-Textile Origami Dipole Antennas With Graded Embroidery for Adaptive RF Performance

Statistical quantification of DC power generated by bistable piezoelectric energy harvesters when driven by random excitations

In contrast to monitoring natural frequency shift, bifurcation-based sensing techniques utilize dramatic switches in response amplitude to detect structural change. We demonstrate a highly sensitive bifurcation-based sensing method requiring only the monitored structure, a transduction mechanism, and bistable electric circuitry. The system configuration is broadly applicable from, e.g., microscale mass sensing to structural health monitoring. In contrast to single bifurcation events of past techniques, the present methodology introduces new bifurcations that may be utilized sequentially for monitoring numerous thresholds of structural parameter change. We show that bifurcation-based sensing potential and versatility is greatly advanced.

Robust sensing methodology for detecting change with bistable circuitry dynamics tailoring

Developing energy harvesting platforms that are strongly sensitive to the low and diffused frequency spectra of common environmental vibration sources is a research objective receiving great recent attention. It has been found that utilizing designs and incorporating structural influences that induce small values of linear stiffness may considerably enhance the power generation capabilities of energy harvesting systems. This research examines these two factors in new light toward the development of a biologically-inspired energy harvesting beam platform that exploits axial compressive effects and compliant suspensions. Through theory and experiments, it is found that the strategic exploitation of such characteristics promotes dramatic improvements in the average power that may be generated for the same excitation conditions. Examining the origin of these performance enhancements, it is seen that large compliance in the compressed axial suspensions facilitates a favorable redistribution of dynamic energy, which thereby enables greater bending of the harvester beam and increased electromechanical transduction. [DOI: 10.1115/1.4031412]

Ryan L. Harne

Papers

Adaptive magnetoelastic metamaterials: A new class of magnetorheological elastomers:

E-Textile Origami Dipole Antennas With Graded Embroidery for Adaptive RF Performance

Statistical quantification of DC power generated by bistable piezoelectric energy harvesters when driven by random excitations

Robust sensing methodology for detecting change with bistable circuitry dynamics tailoring

Axial Suspension Compliance and Compression for Enhancing Performance of a Nonlinear Vibration Energy Harvesting Beam System