Tunable Energy Harvester Research Articles

Strong magnetoelectric coupling in novel Na0.5Bi0.5TiO3–BaFe12-2xCoxTixO19 multiferroic composite

Multiferroic composites of sol-gel synthesized Sodium Bismuth Titanate (Na0.5Bi0.5TiO3) and Co–Ti substituted Barium Hexaferrite (BaFe12-2xCoxTixO19; x = 0.0, 0.5, 1.0, 1.5 and 2.0) in the ratio 3:1 was synthesized through ceramic route. Successful formation of R3c rhombohedral and P63/mmc hexagonal phases corresponding to Na0.5Bi0.5TiO3 and BaFe12-2xCoxTixO19 respectively was confirmed from the XRD and Rietveld refinement pattern. The frequency and temperature dependence of dielectric constant and loss of the composite systems exhibited typical dispersion behaviour which could be understood using the Maxwell-Wagner model. Substituted samples showed enhanced dielectric behaviour where dielectric constant was observed to increase while loss tangent decreased. Using the Universal Jonscher's Power law (JPL), conductivition mechanisms of the composite systems were studied from the ac conductivity behaviour which revealed that the x = 0.0 sample followed Non-overlapping Small Polaron Tunnelling (NSPT) model while the remaining samples followed the Correlated Barrier Hopping (CBH) model. The complex impedance and Nyquist plot analysis showed the enhancement of resistive property in the x≠0 systems. Magnetic hysteresis loop measurements were conducted, and the associated parameters were determined with the assistance of the Law of Approach to Saturation (LAS). Favourable reduction in the magnetic anisotropy was observed indicating the disturbance of magnetic spin structure in the hexaferrite phase. The P-E loops established the novel room temperature multiferroic nature of the composite systems. Significant magnetoelectric coupling was detected at room temperature in all samples, with the x = 0.5 sample exhibiting the highest value of approximately 59.81 mV/cmOe. These desirable properties suggest that the composites may find future device applications as in magnetically tunable energy harvesting devices and self-powered magnetoelectric sensors in the future.

Tunable topological edge states and energy harvesting of piezoelectric-inductance phononic crystals based on Su-Schrieffer-Heeger model

Based on Su-Schrieffer-Heeger (SSH) model, a one-dimensional tunable topological phononic crystal (PnC) was designed. Piezoelectric column with an inductance was designed as a scatterer embedded in the epoxy resin matrix. And the introduce of an inductance into each piezoelectric column resulted in a new Dirac point in band structure. Subsequently, the new Dirac point was operated to open/close by altering the intracell distance, and the trivial and non-trivial phase transition occurred simultaneously, which demonstrated the topological properties of PnC. The results showed that the obvious edge state was observed at the frequencies of 16.334–27.226 kHz by varying the inductance from 2.5mH to 9.5mH. And the immune of the edge state to the local defects was also verified. Furthermore, the energy harvesting of the wave propagation was performed, and the energy harvesting efficiency of the edge state case was about 40 times larger than that of bulk state case.

Elastic foundation-introduced defective phononic crystals for tunable energy harvesting

Defective phononic crystals offer the advantage of concentrating elastic waves, thereby enhancing the potential for piezoelectric energy harvesting (PEH). However, a key limitation is their reliance on a fixed operating frequency, rendering them susceptible to the prevailing vibration environment. To surmount this constraint, this study introduces a novel approach involving a tunable elastic foundation system for defective phononic crystal structures. The newly developed phononic crystal is fashioned by integrating a periodically elastic foundation beneath a uniform beam. A defect is induced by selectively removing specific elastic foundations and integrating piezoelectric components. Explicit analytical solutions are established through the transfer matrix method and the spectral element method, which are subsequently corroborated via comparison with finite element results. The findings underscore that the periodic elastic foundations impart bandgaps in the elastic wave band structure. The absence of specific elastic foundations results in the emergence of distinct defect modes. Additionally, frequency response analysis exposes the potential for energy enhancement, albeit with inherent variations. Noteworthy is the revelation that manipulating the stiffness of the elastic foundation triggers shifts in the resonant frequency of the output voltage. Therefore, the proposed tunable elastic foundation system exhibits promising potential to engender versatile and adaptive phononic crystal configurations, thereby advancing the domain of PEH.

Magnetoelectric Composites: Engineering for Tunable Filters and Energy Harvesting Applications

Multiferroic ceramic composites have been engineered to incorporate multiple desired physical properties within a single ceramic component. The objective of this study was to create such composites through pressure less sintering ferroelectric-doped PZT and nickel–zinc ferrite at a temperature of 1250 °C. The growth of ferrite grains was found to be influenced by the concentration of the ferroelectric PZT phase. Consequently, an increase in the ferrite content decreased the average particle size of nickel–zinc ferrite by a factor of 1.8. After impedance spectroscopy, the multiferroic ceramic composites can be categorized into two groups: those with low ferrite content (<20%) and those with a high ferrite content (>20%). Composites with a high ferrite content are suitable for dual-band filters or shield applications. The impedance spectroscopy analysis revealed that the resonance frequency can be shifted to higher frequency ranges. Therefore, it was demonstrated that modifying the composition of the multiferroic composite allows for tailoring the impedance behavior to shield living and working spaces against such radiation to meet the demands of the 21st century.

Flexible structural polyethylene films for dynamically tunable energy harvesting from the sun and outer space

Passive daytime radiative cooling (PDRC) achieves a sub-ambient temperature without any electricity input, which is of great significance for global energy savings and minimum carbon footprint, especially, in hot seasons. However, due to the static performance of most PDRC materials, it may cause overcooling and high heating energy consumption in cold seasons. Here we establish a structural surface on ubiquitous polyethylene (PE) films and demonstrate an asymmetric electromagnetic transmission with forward/backward transmittance ratios of 2.61 and 1.67 in both solar irradiance and long-wave infrared (LWIR) spectral ranges, enabling it to work as a multispectral self-adaptive window (MSW). By integrating the MSW with the PDRC material, the originally static PDRC can be transformed into a dynamic one that allows the switching between temperatures 4.3 °C lower and 3.4 °C higher than the ambient temperature of the chamber interior. The cooling and heating modes are achieved through electrically actuating the MSW, which originates from the dynamically tunable energy harvesting from the sun and outer space. The MSW features transition-temperature-independent switching, broad spectral tunability, lightweight, robust mechanical strength, low cost, and scalable manufacturability, benefiting both an in-depth insight into the dynamical interaction of terrestrial objects with nature thermodynamics resources and broad applications.

A tunable rotational energy harvester exploiting a flexible-clamping piezoelectric beam by deploying magnetic repulsive force

A tunable rotational energy harvester exploiting a flexible-clamping piezoelectric beam by deploying magnetic repulsive force

Tunable energy harvesting vibration absorber with liquid-metal filled elastic chamber

This paper presents a novel tunable energy harvesting vibration absorber with liquid-metal filled elastic chamber (TEHVA-LMEC) for simultaneously achieving tuned energy harvesting and semi-active vibration suppression. This device consists of a rigid chamber covered with two rubber membranes, two parallel magnets, copper bar electrodes, and liquid metal filled inside the chamber. Liquid metal functions both as the core component for electromagnetic energy harvest, i.e. cutting the magnetic induction lines and producing electricity, and in the meantime provides inertia as liquid mass for vibration suppression. Therefore, TEHVA-LMEC inherits the advantages of both liquid-mass tuned vibration absorbers (TVAs) and electromagnetic energy harvesters, including weight efficiency, simpler tuning procedure, and larger power output with lower internal impedance. More importantly, the natural frequency and the optimal energy harvesting frequency of TEHVA-LMEC are adjusted synchronously, which is beneficial in engineering applications where external excitation and the primary structure’s dynamic characteristics are not constant. A single-degree-of-freedom (SDOF) analytical model of TEHVA-LMEC is proposed for the discussions of its output voltage and natural frequency. A parameter investigation reveals that the rated output voltage can be designed by adjusting two design parameters. A prototype based on the analytical model is tested on an electrodynamic shaker. Experiments evaluated the electromagnetic energy harvesting function and its characteristic with different vibrating frequencies. Both tuned energy harvesting and vibration absorption functions of TEHVA-LMEC are verified.

Verification and analysis of advanced tuneable nonlinear vibration energy harvester

This paper deals with advanced techniques of transducing kinetic energy of vibration into useful electricity. Piezoelectricity is widely used as one of the conversion principles and nonlinearities are studied. Motivated by possible applications in aircraft or railways, we seek to find the best system configuration for various forcing conditions to maximize the power generation for more advanced wireless sensing stations. The results for vibration amplitude 0.5 g indicate that monostable regime is suitable for tuning for frequencies lower than the natural frequency of the linear resonator. The best type of oscillation for bistable regime is always in-well single-periodic behavior and is suitable for tuning in the entire frequency range from 20 to 65 Hz. The results show the versatility of this simple energy harvester and could serve as theoretical background for a new tunable energy harvester that will be able to adapt to changes in excitation. This design could also be used in smart sensing structures.

Bandwidth tunable vibration energy harvester based on hybrid triboelectric-piezoelectric array

In this work, we present a highly effective and scalable design strategy of a triboelectric-piezoelectric hybrid array of three cantilever beams stacked over each other (wideband operation regime), which can also be rotated around their mean position to vibrate freely without impacting any other layer (narrowband operation regime). Contrary to a unique frequency response exhibited by conventional devices, the proposed device can switch between narrowband and wideband frequency responses around different central frequencies. This work elaborately discusses the frequency response of mechanical stopper-based PEG and TEGs at varying gap lengths, excitations, and resonant frequencies, and the design of the hybrid array is optimized based on it. The performance of this device is characterized using simulation analysis and experimental validation. Experimentally, the device generates net power greater than 0.3 μW (Piezoelectric) and 0.4 μW (Triboelectric) continually between the frequencies of 30 to 60 Hz in the wideband operation regime and output power of 0.81 μW, 0.65 μW, and 0.62 μW at 27,36 and 45 Hz in the narrowband operation regime under mechanical excitation of 0.75g. The remarkable performance of the device at different frequency ranges demonstrates its potential in various harvesting and sensing applications.

Tunable topological interface states and resonance states of surface waves based on the shape memory alloy

Topological interface state (TIS) of elastic wave has attracted significant research interest due to its potential prospects in strengthening acoustic energy and enhancing the signal accuracy of damage identification and quantification. However, previous implementations on the interface modes of surface waves are limited to the non-adjustable frequency band and unalterable mode width. Here, we demonstrate the tunable TIS and topological resonance state (TRS) of Rayleigh wave by using a shape memory alloy (SMA) stubbed semi-infinite one-dimensional (1D) solid phononic crystals (PnCs), which simultaneously possesses the adjustable mode width. The mechanism of tunability stems from the phase transformation of the SMA between the martensite at low temperature and the austenite at high temperature. The tunable TIS of Rayleigh wave is realized by combining two bandgap-opened PnCs with different Zak phases. The TRS with adjustable mode width is achieved in the heterostructures by adding PnCs with Dirac point to the middle of two bandgap-opened PnCs with different Zak phases, which exhibits the extraordinary robustness in contrast to the ordinary Fabry–Pérot resonance state. This research provides new possibilities for the highly adjustable Rayleigh wave manipulation and find promising applications such as tunable energy harvesters, wide-mode filters, and high-sensitivity Rayleigh wave detectors.

Tunable spring balanced magnetic energy harvester for low frequencies and small displacements

In this paper we present a novel concept to efficiently harvest vibrational energy at low frequencies and very small displacement. We describe and evaluate an electromagnetic energy harvester which generates power from a magnetic circuit with motion induced variations of an air gap. External vibrations induce oscillations of the gap length around an equilibrium point, due to a linear spring counteracting the magnetic force. The relative position of the spring can be adjusted to optimize the harvester output for excitation amplitude and frequency. A simulation model is built in COMSOL and verified by comparison with lab measurements. The simulation model is used to determine the potential performance of the proposed concept under both harmonic and non-harmonic excitation. Under harmonic excitation, we achieve a simulated RMS load power of 26.5 μW at 22 Hz and 0.028 g acceleration amplitude. From a set of comparable EH we achieve the highest theoretical power metric of 1712.2 µW/cm3/g2 while maintaining the largest relative bandwidth of 81.8%. Using measured non-harmonic vibration data, with a mean acceleration of 0.039 g, resulted in a mean power of 52 μW. Moreover, the simplicity and robustness of our design makes it a competitive alternative for use in practical situations.

Improving energy harvesting from impulsive excitations by a nonlinear tunable bistable energy harvester

This paper proposes a novel prototype of tunable bistable energy harvester (TBEH) coupled to a grounded and weakly damped linear primary structure. Based on buckling beam theory and generalized Hamiltonian principle, the equivalent mathematical model of the proposed TBEH system is presented and numerically simulated. A thorough sensitivity analysis concerning the buckled factor, the mass ratio, magnitude of impulse and the impulse period is studied to provide design insights for dynamic optimization of the TBEH system excited by varying impulsive excitations. The influences of a single impulse and repeated impulses on the vibration suppression and energy harvesting performance of TBEH system are investigated, respectively. Furthermore, the dynamics of the primary structure and TBEH and percentage of transient total energy in the TBEH are presented. The results show that maximizing measures of vibration energy absorption and harvesting can be optimized by tuning the sensitive parameters of the TBEH system. Compared with the pure cubic case, the tunable buckled TBEH shows remarkable advances in broadband vibration absorption and fast energy transfer. Finally, the confirmatory prototype experiment is conducted to validate the theoretical results. The measured experimental results are in good agreements with the theoretical analysis. The proposed TBEH with excellent energy capture and conversion is a potential alternative for powering miniature wireless sensor networks.

Interface-dependent tunable elastic interface states in soft metamaterials

Elastic interface states, which are usually generated at the interface of two connected domains with opposite topological invariant, have been successfully demonstrated in periodic structures. Therefore, the interface states determined by the position of interface between two domain walls in one-dimensional elastic systems are rarely reported, which were mainly restricted by the mirror-symmetric geometry of the unit cell. Jointing interface-dependent interface states were mostly implemented with analogs of quantum valley Hall effects in two-dimensional systems. Herein, we first observe two types of elastic interface states simultaneously occurred in one-dimensional combined metamaterials, where two interface modes separately located at two connected domain walls and they can be actively tuned simply through deforming two components on two sides. Flexible and versatile frequency shift and switch on–off characteristics of combination of two interface modes are demonstrated, which may be employed in the multifunctional elastic wave filters, tunable energy harvesting, and elastography devices. Our primitive cell of the soft metamaterial, which breaks the inversion symmetry along the horizontal direction, may be generalized to realize tunable elastic valley Hall edge states.

Low-frequency tunable topological interface states in soft phononic crystal cylinders

Topological phononic crystals have attracted intensive attention due to their peculiar topologically protected interface or edge states. Their operating frequency, however, is generally fixed once designed and fabricated. Here, we propose to overcome this limitation by utilizing soft topological phononic crystals. In particular, we design a simple one-dimensional periodic system of soft cylindrical waveguides to realize mechanically tunable topological interface states for longitudinal waves. To this end, we employ the nonlinear elasticity theory and its linearized incremental version to fully account for both geometric and material nonlinearities of the system. We derive the dispersion relation for small-amplitude longitudinal motions superimposed on the finitely deformed state. In addition, our analytical results provide information about the corresponding Bloch wave modes, displacement field distributions, and signal transmission coefficients for finite cylindrical waveguides with identical or various unit-cell topologies. Our numerical results illustrate the low-frequency topological interface state occurring at the interface between two topologically distinct soft phononic cylinders. Moreover, we show that the corresponding frequency in the overlapped band gap can be continuously adjusted by an external force. This analytical result is also validated by the finite element simulations. Finally, we provide the topological phase diagrams to demonstrate the tunable position and existence condition of the topological interface states when tuning the external loading. The low-frequency tunable topological interface states with remarkable field enhancement may find a wide range of potential applications such as tunable energy harvesters, low-pass filters and high-sensitivity detectors for biomedical applications.

Tunable yo-yo energy harvester with oblique springs

In this study, a yo-yo vibrational energy harvesting device that can adjust its resonant frequency to the desired excitation frequency using geometrical control is proposed and investigated. The device employs a spring system, suspended proof mass, and set of reels and gears to convert translational input into rotational motion to power its generator. The spring system is composed of two symmetrical oblique springs, and its stiffness and the resonant frequency of the proposed harvester varies with the oblique angle between these springs. The characteristics of the oblique spring system are investigated accordingly, and it is shown that there exists a lower limit of stiffness; therefore, the achievable frequency bandwidth of the harvester can be determined. The method used to design the proposed tunable energy harvester so that it satisfies the desired frequency bandwidth is then provided. A prototype of the device was built and tested on a vibration table, and its performance is illustrated via a comparison with the results of numerical calculations. The results indicate that the proposed device is capable of harnessing the kinetic energy of the ocean waves.

Tunable, multi-modal, and multi-directional vibration energy harvester based on three-dimensional architected metastructures

Conventional vibration energy harvesters based on two-dimensional planar layouts have limited harvesting capacities due to narrow frequency bandwidth and because their vibratory motion is mainly restricted to one plane. Three-dimensional architected structures and advanced materials with multifunctional properties are being developed in a broad range of technological fields. Structural topologies exploiting compressive buckling deformation mechanisms however provide a versatile route to transform planar structures into sophisticated three-dimensional architectures and functional devices. Designed geometries and Kirigami cut patterns defined on planar precursors contribute to the controlled formation of diverse three-dimensional forms. In this work, we propose an energy harvesting system with tunable dynamic properties, where piezoelectric materials are integrated and strategically designed into three-dimensional compliant architected metastructures. This concept enables energy scavenging from vibrations not only in multiple directions but also across a broad frequency bandwidth, thus increasing the energy harvesting efficiency. The proposed system comprises a buckled ribbon with optional Kirigami cuts. This platform enables the induction of vibration modes across a wide range of resonance frequencies and in arbitrary directions, mechanically coupling with four cantilever piezoelectric beams to capture vibrations. The multi-modal and multi-directional harvesting performance of the proposed configurations has been demonstrated in comparison with planar systems. The results suggest this is a facile strategy for the realization of compliant and high-performance energy harvesting and advanced electronics systems based on mechanically assembled platforms.

Tunable pyroelectricity, depolarization temperature and energy harvesting density in Pb(Lu0.5Nb0.5)O3-xPbTiO3 ceramics

The ferroelectric to antiferroelectric (FE-AFE) phase boundary design based on orthorhombic AFE phase and tetragonal FE phase is an effective method to develop high-performance pyroelectric materials due to the complete release of large electrical polarization in FE-AFE phase transition. Herein, we report the phase structure evolution in (1-x)Pb(Lu0.5Nb0.5)O3-xPbTiO3 (abbreviated as PLNT100x) ceramic system based on the relationship of tolerance factors versus electronegativity differences. The composition/temperature effects on FE-AFE phase transition behavior, pyroelectricity, depolarization temperature (Td) and energy harvesting performance were investigated systematically. Obviously, PLNT system displays superior pyroelectric characteristics as well as high Td. The maximum pyroelectric peak was 4.50 μC·cm−2·K − 1 over a wide temperature range from 28 °C to 167 °C. In addition, the obtained maximum pyroelectric energy harvesting density was 1.66 J/cm3 which was much higher than the currently reported values, indicating a potential candidate for pyroelectric energy conversion applications. Based on the modified Ginzburg−Landau−Devonshire (GLD) phenomenology, the composition/temperature driven phase transitions were discussed, and the temperature−electric field (T − E) phase diagram was accordance with actual phase diagram based on the experimental data.

Vibration-Energy-Harvesting System: Transduction Mechanisms, Frequency Tuning Techniques, and Biomechanical Applications.

Vibration-based energy-harvesting technology, as an alternative power source, represents one of the most promising solutions to the problem of battery capacity limitations in wearable and implantable electronics, in particular implantable biomedical devices. Four primary energy transduction mechanisms are reviewed, namely piezoelectric, electromagnetic, electrostatic, and triboelectric mechanisms for vibration-based energy harvesters. Through generic modeling and analyses, it is shown that various approaches can be used to tune the operation bandwidth to collect appreciable power. Recent progress in biomechanical energy harvesters is also shown by utilizing various types of motion from bodies and organs of humans and animals. To conclude, perspectives on next-generation energy-harvesting systems are given, whereby the ultimate intelligent, autonomous, and tunable energy harvesters will provide a new energy platform for electronics and wearable and implantable medical devices.

Tunable multi-source energy harvesting via frequency selective structures

In this paper, a novel vibrational energy harvesting device based on frequency selective structures (FSS) with piezoelectric transducers is originally explored. The FSS is a dynamically tailored structural element enabling the required acoustic focusing via vibration localization at prescribed structural areas. This mechanism results in structural areas with the high energy density that can be effectively exploited to develop enhanced vibration-based energy harvesting. In addition, this approach allows to induce localized responses in different structural areas simply by tuning the frequency of the active excitation produced by a single transducer, which is able to achieve multi-source energy harvesting. Fully coupled electromechanical models of the FSS tapered structure with surface mounted piezoelectric transducers are used to numerically simulate the response of the system under the steady-state response and the transient response. The designed performances are numerically evaluated using voltage and power produced by the piezoelectric transducer networks. Results show that the dynamically tailored FSS design enables a multi-source energy harvesting.

Optimization-Based Approach for the Inverse Design of Ribbon-Shaped Three-Dimensional Structures Assembled Through Compressive Buckling

Mechanically guided assembly through compressive buckling emerges as a viable approach to fabricate complex three-dimensional (3D) mesostructures and functional devices. However, it remains a challenge to efficiently and accurately find the 2D precursor of a desired 3D structure. The authors propose a systematic computational method based on an adaptive genetic algorithm, and solve this inverse design problem for ribbon-shaped 3D structures. This work has a broad range of applications in the design optimization of ribbon-shaped 3D microelectronic devices, such as tunable antennas and energy harvesters.