Electromechanical Energy Harvester Research Articles

Frequency conversion interposer with no-internal stress curved-beam for MEMS vibrational energy harvesters

The generating efficiency of an micro electro mechanical system vibrational energy harvester (MEMS VEH), which converts vibrational energy into electrical energy, is maximized at resonance. However, because the resonance frequency of an MEMS VEH is an order of magnitude higher than the vibrational frequency in the environment and not only has a high Q value, but the frequency of vibration in the environment changes randomly, it is difficult for MEMS VEHs to harvest vibrational energy efficiently. In this study, we propose a method to improve the generation efficiency of MEMS VEHs using a Frequency Conversion Interposer (FCI) that vibrates nonlinearly with its bistable no-internal stress curved-beam. As a simulation model combining FCI with the MEMS VEH, we fabricated a Two-Dimensional Monolithic Structure (TDMS) with a curved-beam and a straight beam that mimicked the FCI and oscillatory structure of the MEMS VEH, respectively. It was observed that the vibration of the straight beam induced snap-through (ST) of the curved-beam of the FCI, and the measured acceleration was more than 1.3 times the applied acceleration applied from the FCI to the MEMS VEH. As the power generation of the MEMS VEH is proportional to the square of the applied acceleration, the FCI is useful for improving the generating efficiency of the MEMS VEH.

High-performance piezoelectric energy harvesting in amorphous perovskite thin films deposited directly on a plastic substrate

Most reported thin-film piezoelectric energy harvesters have been based on cantilever-type crystalline ferroelectric oxide thin films deposited on rigid substrates, which utilize vibrational input sources. Herein, we introduce flexible amorphous thin-film energy harvesters based on perovskite CaCu3Ti4O12 (CCTO) thin films on a plastic substrate for highly competitive electromechanical energy harvesting. The room-temperature sputtering of CCTO thin films enable the use of plastic substrates to secure reliable flexibility, which has not been available thus far. Surprisingly, the resultant amorphous nature of the films results in an output voltage and power density of ~38.7 V and ~2.8 × 106 μW cm−3, respectively, which break the previously reported record for typical polycrystalline ferroelectric oxide thin-film cantilevers. The origin of this excellent electromechanical energy conversion is systematically explored as being related to the localized permanent dipoles of TiO6 octahedra and lowered dielectric constant in the amorphous state, depending on the stoichiometry and defect states. This is the leading example of a high-performance flexible piezoelectric energy harvester based on perovskite oxides not requiring a complex process for transferring films onto a plastic substrate.

Multiscale topology optimization of an electromechanical dynamic energy harvester made of non-piezoelectric material

Multiscale topology optimization of an electromechanical dynamic energy harvester made of non-piezoelectric material

Kinetic Vibration Energy Harvester Based on Electromechanical Converter with Power Electronics Active Rectifier

Electromechanical energy harvesters are used to extract energy from vibrations occurring in nature, transport, or industry. The main problem with such solutions is that their output voltage is completely dependent on the frequency and amplitude of the vibrations, which can make it difficult to power a specific device or charge a battery. Therefore, it is necessary to use solutions that meet these requirements. Most harvesters contain additional, specialized mechanical gearboxes, called mechanical rectifiers or power electronic interfaces, used to match the harvester’s output voltage to the load. Design work was carried out, the construction of the proposed energy harvester was described, and the operation principle of the author’s control algorithm was presented. The results of the research confirm the possibilities of influencing the output voltage and power of the harvester system independently of the frequency and excitation amplitude.

The Electro-Mechanical Energy Harvesting Configurations in Different Modes from Machine to Self-Powered Wearable Electronics

The Electro-Mechanical Energy Harvesting Configurations in Different Modes from Machine to Self-Powered Wearable Electronics

Low-temperature co-fired multilayer cantilevers based on relaxor–Pb(Zr,Ti)O3 for enhanced piezoelectric power generation at nonresonant frequency

Improving piezoelectric power-generation capability has been explored by modulating materials chemistry and device structure for specific low-power applications. Herein, high-performance multilayer cantilever structures based on perovskite 0.4Pb(Zn1/3Nb2/3)O3–0.6Pb(Zr0.5Ti0.5)O3 (0.4PZN–0.6PZT) with CuO additives are proposed as an example of electromechanical energy harvester utilizing nonresonant-frequency mechanical source. Even with low-temperature co-firing at 900 °C for 2 h to use inexpensive Ag inner electrodes, an optimized unimorph single-layer cantilever exhibited the best normalized power density of ∼10.8 mW cm−2 g−2 Hz−1 at 2 Hz with an acceleration of 0.028 g, which is far better than typical values reported for cantilever harvesters. The power value itself increased from ∼142.7 to ∼508.5 μW with four layers while maintaining the high power density. The enhanced power with multilayers was attributed to the increased current due to extensive surface-charge polarization as the effective electrode coverage area was approximately quadrupled.

The mechanism parts of mechanical motion rectifier to produce energy from third pedal in automotive

Energy harvesting architectures, such as wind turbines and solar panels, have become a necessity as renewable energy sources have grown in popularity. The most promising source of electric energy appears to be electromechanical energy harvesting, as it generates significant amounts of electricity that can be utilized in numerous ways. This research supports and supplements the automotive, regardless of how much and how effectively power is generated. Essentially, when the driver touches the throttle or brake pedal, the energy-harvesting pedal receives motion from them through a mechanical connection rod. Considering its utility in charging electric cars, it is considered one of the most useful sources of electricity.

Effective electromechanical properties and energy harvesting response in PMN-0.3PT/PDMS flexible piezoelectric composites: a combined experimental and theoretical study

In this work, lead magnesium niobate-lead titanate (PMN-0.3PT) and polydimethylsiloxane (PDMS)-based flexible piezoelectric-polymer composites are designd and developd for efficient mechanical energy harvesting through a combined experimental-theoretical approach. A solid-state reaction method was employed to synthesize PMN-0.3PT piezo-ceramic, which was subsequently used for the fabrication of -PMN-0.3PT/PDMS piezoelectric-polymer 0–3 composite with different volume fractions, = 0.03, 0.25, and 0.50 of PMN-0.3PT reinforcement. Uniformly distributed PMN-0.3PT particles were found to retain their structural symmetry across the volume fractions and are well adhered to the PDMS matrix. The effective electromechanical properties of the composites were measured and compared with model predictions employing the finite element method and Eshelby–Mori–Tanaka-based micromechanical models. Considering that flexibility is a critical design parameter, we propose a new figure-of-merit term that would consider both electromechanical conversion as well as the mechanical flexibility of the material. We show that at = 0.5, PMN-0.3PT/PDMS 0–3 composite yields an optimum combination of energy harvesting performance and flexibility. Our study further demonstrates that the orientation of the PMN-0.3PT particles does not significantly influence the effective elastic and dielectric properties at low and moderate PMN-PT content, attributed to the lower aspect ratio of the reinforcement particles. The piezoelectric charge coefficient showed small yet finite change with increasing reinforcement content. A maximum current density, 35 nA cm−2, and electric field, 90 V cm−1, was obtained with a cyclic compressive stress of 0.22 MPa (force, 50 N) at 5 Hz, in a piezoelectric generator, based on = 0.5.

Investigation Into the Effect of Joint Clearance on the Dynamics of a Biomechanical Energy Harvesting System

The existing clearance in the mechanical joints plays a crucial role in the assembly of mechanical systems, allowing the mobility of its components. However, few studies have explored models that consider joint clearance in the case of electromechanical energy harvesting systems. This paper examines the effect of existing clearance in an electromagnetic energy harvester attached to the human lower limb. The dynamic response of the system and an estimate of its generated power are obtained by developing a lumped model, in which clearance is included by adding a dead band and assigning a stiffness coefficient during contact between elements. The natural motion of the lower limb is the input to the formulated model, which takes into account the nonlinear interaction of the electromagnetic device and the power conditioning circuit. Central composite design is used to study the influence of two selected factors on the dynamics of the system; joint clearance size and contact stiffness. The results suggest that the presence of clearance between the clamping mechanism and the human body positively affects the performance of the analyzed electromagnetic energy harvesting system. It was revealed that an increase of around 27% of output power could be intentionally achieved by adding larger clearance sizes.

Anion-Dependent Polarization and Piezoelectric Power Generation in Hybrid Halide MAPbX3 (X = I, Br, and Cl) Thin Films with Out-of-Plane Structural Adjustments.

Anion-dependent differences in the electromechanical energy harvesting capability of perovskite halides have not been experimentally demonstrated thus far. Herein, anion-dependent piezoelectricity and bending-driven power generation in high-quality methylammonium lead halide MAPbX3 (X = I, Br, and Cl) thin films are explored; additionally, anisotropic in situ strain is imposed to improve energy harvesting under tensile bending. After applying the maximum in situ strain of -0.73% for all the halide thin films, the MAPbI3 thin-film harvester exhibited a peak voltage/current of ≈23.1V/≈1703 nA as the best values, whereas MAPbBr3 and MAPbCl3 demonstrated ≈5.6V/≈176 nA and ≈3.3V/≈141 nA, respectively, under identical bending conditions. Apart from apparent ferroelectricity of tetragonal MAPbI3 , origin of the piezoelectricity in both cubic MAPbBr3 and MAPbCl3 is explored as being related to organic-inorganic hydrogen bonding, lattice distortion, and ionic migration, with experimental supports of effective piezoelectric coefficient and grain boundary potential. Conclusively, piezoelectricity of the cubic halides is assumed to be due to their soft polarity modes and relatively low elastic modulus with vacancies contributing to space-charge polarization. In the case of ferroelectric MAPbI3 , the distortion of PbI6 octahedra and atomic displacement within each octahedron are quantitatively estimated.

A Magnetically Coupled Piezoelectric-Electromagnetic Low-Frequency Multidirection Hybrid Energy Harvester.

The traditional single electromechanical conversion energy harvester can collect energy only in a single vibration direction. Moreover, it requires high environmental vibration frequency, and its output power is low. To solve these problems, a cross-shaped magnetically coupled piezoelectric–electromagnetic hybrid harvester is proposed. The harvester comprised a ring-shaped support frame, a piezoelectric generation structure, and an electromagnetic generation structure. The harvester could simultaneously generate energy piezoelectrically and electrically, in addition, it could generate electricity efficiently at a lower environmental vibration, and it can collect the energy in two vibration directions simultaneously. To verify the effectiveness of the device, we set up a vibration experiment system and conducted comparative experiments about non-magnetically coupled piezoelectric, magnetically coupled piezoelectric, and magnetically coupled piezoelectric–electromagnetic hybrid energy harvesters. The experimental results showed that the output power of the magnetically coupled piezoelectric–electromagnetic hybrid energy harvester was 2.13 mW for the piezoelectric structure and 1.76 mW for the electromagnetic structure under the vibration of single-direction resonant frequency. The total hybrid output power was 3.89 mW. The hybrid harvester could collect vibration energy parallel to the ring in any direction. Furthermore, compared with the non-magnetically coupled piezoelectric energy harvester and the magnetically coupled piezoelectric energy harvester, the output power was increased by 141.6% and 55.6%, respectively.

3D Printing of Composite Material for Electromechanical Energy Harvesters

In this paper, a novel, composite material is proposed based on ferromagnetic wires immersed in a polymer that is well suited for 3D printing. The magnetic properties of this material are examined using FEM and compared with the properties of a more traditional composite based on magnetic powder. For a 50% ferromagnetic volume in the material, the proposed composite has a 67% higher value of saturation magnetic flux density and 87% higher value of maximum permeability, compared with the powder-based material. The authors believe that the proposed material could be used in the manufacturing of small electromechanical devices such as energy harvesters, thus vastly widening the possible fields of application related to 3D printing techniques.

Nanoampere‐Level Piezoelectric Energy Harvesting Performance of Lithography‐Free Centimeter‐Scale MoS2 Monolayer Film Generators

2D transition-metal dichalcogenides have been reported to possess piezoelectricity due to their lack of inversion symmetry; thus, they are potentially applicable as electromechanical energy harvesters. Herein, the authors propose a lithography-free piezoelectric energy harvester composed of centimeter-scale MoS2 monolayer films with an interdigitated electrode pattern that is enabled only by the large scale of the film. High-quality large-scale synthesis of the monolayer films is conducted by low-pressure chemical vapor deposition with the assistance of an unprecedented Na2 S promoter. The extra sulfur supplied by Na2 S critically passivates the sulfur vacancies. The energy harvester having a large active area of ≈18.3mm2 demonstrates an unexpectedly high piezoelectric energy harvesting performance of ≈400.4mV and ≈40.7nA under a bending strain of 0.57%, with the careful adjustment of side electrodes along the zigzag atomic arrays in the two dominant domain structure. Nanoampere-level harvesting has not yet been reported with any 2D material-based harvester.

Combining Solid-State Shear Milling and FFF 3D-Printing Strategy to Fabricate High-Performance Biomimetic Wearable Fish-Scale PVDF-Based Piezoelectric Energy Harvesters.

High-performance flexible piezoelectric polymer-ceramic composites are in high demand for increasing wearable energy-harvesting applications. In this work, a strategy combining solid-state shear milling (S3M) and fused filament fabrication (FFF) 3D-printing technology is proposed for the fabrication of high-performance biomimetic wearable piezoelectric poly(vinylidene fluoride) (PVDF)/tetraphenylphosphonium chloride (TPPC)/barium titanate (BaTiO3) nanocomposite energy harvesters with a biomimetic fish-scale-like metamaterial. The S3M technology could greatly improve the dispersion of BaTiO3 sub-micrometer particles and the interfacial compatibility, resulting in better processability and piezoelectric performance of the nanocomposites. Typically, the FFF 3D printed energy harvester incorporating 30 wt % BaTiO3 showed the highest piezoelectric outputs with an open-circuit voltage of 11.5 V and a short-circuit current of 220 nA. It could hence drive nine green LEDs to work normally. In addition, a 3D-printed biomimetic wearable energy harvester inspired by an environmentally adaptive fish-scale-like metamaterial was further fabricated. The fish-scale-like energy harvester could harvest energy through different deformation motions and successfully recharge a 4.7 μF capacitor by being mounted on a bicycle tire and the tire's rolling. This work not only provides a 3D printing strategy for designing diversified and complex geometric structures but also paves the way for further applications in flexible, wearable, self-powered electromechanical energy harvesters.

Giant Functional Properties in Porous Electroceramics through Additive Manufacturing of Capillary Suspensions

Dedicated hierarchical structuring of functional ceramics can be used to shift the limits of functionality. This work presents the manufacturing of highly open porous, hierarchically structured barium titanate ceramics with 3-3 connectivity via direct ink writing of capillary suspension-type inks. The pore size of the printed struts (∼1 μm) is combined with a printed mesostructure (∼100 μm). The self-organized particle network, driven by strong capillary forces in the ternary solid/fluid/fluid ink, results in a high strut porosity, and the distinct flow properties of the ink allow for printing high strut size to pore size ratios, resulting in total porosities >60%. These unique and highly porous additive manufactured log-pile structures with closed bottom and top layers enable tailored dielectric and electromechanical coupling, resulting in an energy harvesting figure of merit FOM33 more than four times higher than any documented data for barium titanate. This clearly demonstrates that combining additive manufacturing of capillary suspensions in combination with appropriate sintering allows for creation of complex architected 3D structures with unprecedented properties. This opens up opportunities in a broad variety of applications, including electromechanical energy harvesting, electrode materials for batteries or fuel cells, thermoelectrics, or bone tissue engineering with piezoelectrically stimulated cell growth.

Room-temperature processed Ag/Pb(Zn1/3Nb2/3)O3–Pb(Zr0.5Ti0.5)O3-based composites for printable piezoelectric energy harvesters

Piezoelectric energy harvesters based on polymer-matrix composites may be an ideal choice for wearable low-power electronic devices with high flexibility and reliability. Herein, we propose an electromechanical energy harvester consisting of 0.4 Pb(Zn1/3Nb2/3)O3–0.6 Pb(Zr0.5Ti0.5)O3 (PZN–PZT) and Ag nanoparticles dispersed in an ultraviolet (UV)-curable polymer matrix. The harvesters were fabricated by printing a viscous paste, followed by curing at room temperature under UV light. Despite the lack of piezoelectric contribution from the UV-cured polymer, the resultant energy harvesting performance was pronounced with ∼8.15 V and ∼862 nA for the optimized composition of 30 vol% PZN–PZT and 2 vol% Ag, corresponding to approximately 9.4 and 6.5-fold increases, respectively, relative to the values of the reference sample. The enhanced piezoelectric energy harvesting was assumed to originate from contributions of the PZN–PZT nanoparticles as the sole piezoelectric material and the Ag inclusions as a source of additional space-charge polarization.

Effect of uniaxial stress on energy harvesting, storage and electrocaloric performance of BZT ceramics

In this work, a systematic approach of waste (thermal/mechanical) energy harvesting and storage potential is studied in Ba0.85Zr0.15TiO3 (BZT) ceramics. The effect of stress on energy storage density (harvesting/storage) and electrocaloric performance is also studied. For this purpose, polarization–electric field hysteresis loops were recorded at various temperatures and uniaxial compressive stress. The Olsen cycle and electro-mechanical cycle are used for direct waste heat or mechanical energy to electrical energy conversion. A thermal energy-harvesting density of 42 kJ/m3 per cycle was obtained when the Olsen cycle was operated between 296–343 K and 0.25–1.5 MV/m. The electro-mechanical cycle-based energy harvesting is estimated as 78 kJ/m3 under the applied stress of 5–160 MPa and the electric field of 0.25–1.5 MV/m. The energy storage density is found as 39 kJ/m3 at zero stress field and 343 K, which increases to 53 kJ/m3 under the biased stress of 80 MPa in a wide operating temperature range of 296–328 K. It is observed that the high energy storage is a result of the reduction of the hysteresis loss. The electrocaloric temperature is found as 0.16 K and 0.18 K under the 0 and 80 MPa stress fields, respectively. Overall, the reported findings will enrich our understanding of the stress effect on BZT materials, which offers high performance for energy harvesting and storage-based applications. Moreover, this work can be also helpful in improving the energy storage density and electrocaloric effect via stress confinement.

Semi‐active modal control of structures with lockable joints: general methodology and applications

In this study, a novel modal control strategy by means of semi-actively lockable joints is proposed. The control strategy allows for a directed flow of energy between vibrational modes, which makes it suitable not only for vibration attenuation purposes but also for energy scavenging driven by electromechanical energy harvesters. The proposed control strategy is an extension of the prestress-accumulation release (PAR) technique; however, it introduces also new concepts that increase the efficiency of the overall control system. Contrary to the PAR, the proposed method requires measurement of both strains in the vicinity of the semi-active joints and translational velocities that provide global information about system behavior. The latter aspect requires the control system to be organized within a hierarchical feedback architecture. The benefit from this higher complexity of the control system is its better performance compared to the PAR. The proposed semi-active modal control not only attenuates structural vibration faster, but it also achieves this goal with a smaller number of switches implemented in the joints. The effectiveness of the proposed methodology has been demonstrated on structures equipped with two lockable joints. Two practical examples have been investigated: one employs the concept of vibration-based energy harvesting for a two-story frame structure, while the second one reduces vibration of an eight-story frame structure subjected to kinematic excitation.

Stochastic Response Analysis and Reliability-Based Design Optimization of Nonlinear Electromechanical Energy Harvesters With Fractional Derivative Elements

Abstract A methodology based on the Wiener path integral (WPI) technique is developed for stochastic response determination and reliability-based design optimization of a class of nonlinear electromechanical energy harvesters endowed with fractional derivative elements. In this regard, first, the WPI technique is appropriately adapted and enhanced to account both for the singular diffusion matrix and for the fractional derivative modeling of the capacitance in the coupled electromechanical governing equations. Next, a reliability-based design optimization problem is formulated and solved, in conjunction with the WPI technique, for determining the optimal parameters of the harvester. It is noted that the herein proposed definition of the failure probability constraint is particularly suitable for harvester configurations subject to space limitations. Several numerical examples are included, while comparisons with pertinent Monte Carlo simulation (MCS) data demonstrate the satisfactory performance of the methodology.

Electrostatic vibrational energy converter with two variable capacitors

The electrostatic two-capacitor vibration-to-electrical energy converter based on the Bennet doubler circuit with a power source in a variable capacitor branch is studied both theoretically and experimentally. The variations of the capacitances both in opposite phase and in-phase with different modulation depths are considered. Analytical expressions evaluating the energy converter main characteristics and enabling to significantly simplify the optimization process during the converter design are derived. It is shown that the theoretical results are in a good agreement with the obtained experimental data, making it possible to use them for the optimal converter parameters choice when developing electromechanical microgenerators or energy harvesters, active vibration and acceleration sensors, as well as threshold devices. The advantage of the investigated interfacing circuit of the two-capacitor vibration-to-electrical energy converter in comparison with the basic Bennet doubler circuit is the versatility and the ability of the converter to operate under the action of small mechanical vibrations (excitations) causing the capacitance modulation depth less than 2. It is also possible to vary the critical capacitance modulation depth within a rather wide range getting the autostabilization mode even for the capacitance modulation depth greater than 2. As a result, it becomes possible to expand both the range of used amplitudes of external mechanical vibrations and the necessary parameters of the used variable capacitors.