MEMS Piezoelectric Vibration Energy Harvester Research Articles

Enhanced performance on piezoelectric MEMS vibration energy harvester by dynamic magnifier under impulsive force

Vibration energy harvesters that use resonance phenomena exhibit a high output power density for constant frequency vibrations, but they suffer from a significant drop in performance for non-steady-state vibrations, which are important for practical applications. In this work, we demonstrate that the output power under an impulsive force can be increased significantly by placing a U-shaped metal component, called a dynamic magnifier (DM), under an MEMS piezoelectric vibration energy harvester (MEMS-pVEH) with a 6 mm long cantilever using a 3 μm thick Pb(Zr,Ti)O3 film. Based on the results of numerical calculations using a model of pVEH with a two-degree-of-freedom (2DOF) system, the DM was designed to have the same resonant frequency as the MEMS-pVEH and a high mechanical quality factor (Qm). The waveforms of the output voltage of the fabricated 2DOF-pVEHs were measured for impulsive forces with various duration times, and the output power was calculated by integrating the waveforms over time. The output power of the MEMS-pVEH placed on the DM with a Qm of 56 showed a gradual change according to the duration of applying an impulsive force and a maximum of 19 nJ/G2 (G: gravitational acceleration) when the duration of the impulsive force was 3.8 ms. This result was about 90 times greater than the output power of the MEMS-pVEH without a DM. While it is not easy to fabricate pVEHs with a complex 2DOF structure using only the MEMS process, we have demonstrated that the output power can be significantly improved by adding a spring structure to a simple MEMS-pVEH.

Investigation of efficient piezoelectric energy harvesting from impulsive force

This study investigated the electromechanical properties of MEMS piezoelectric vibration energy harvesters (MEMs-pVEHs) under various impulsive forces to discuss effective harvesting energy from random vibrations. MEMS-pVEHs with different resonance frequencies with an energy conversion efficiency close to the theoretical maximum were used. The output waveforms for various impulsive force could be fitted well with the dynamic model of pVEHs. The output energy density reached 34 nJ g−1 for an impulsive force with an acceleration of 8 m s−2. To obtain high energy conversion efficiency, pVEHs should have a response time longer than the duration of the impulsive force; efficiency higher than 50% was obtained by an impulsive force with a short duration. Furthermore, the study investigated the pVEH requirements for impulsive force based on the results of numerical simulation.

A new Tapered-L shaped springs based MEMS piezoelectric vibration energy harvester designed for small rolling bearing fault detection

This paper examines the simulation-based performances of piezoelectric MEMS vibration energy harvester made up of two Tapered-L shaped springs and one seismic mass, which is designed for supplying energy to the bearing fault observing device or else identifying the defect in small bearing. The proposed novel structure having PZT-5A piezoelectric material is designed and analyzed in finite element method simulator COMSOL by utilizing vibration data-based comparison results of healthy and defective bearing from an experimental setup. Time domain analysis, fast Fourier transform, and Morlet wavelet transform are done on acquired vibration signatures to investigate the bearing condition. Experimental results demonstrate 0.09 g and 0.25 g peak acceleration for defect free and defective bearing, respectively. And bearing generated frequency when the ball passes the outer race of the ball bearing is obtained to be 76.3 Hz. Maximum observed power outputs from the Tapered-L shaped device are 22.96 nW and 177.49 nW at 0.09 g and 0.25 g accelerations, respectively over 76.3 Hz resonant frequency and 100 kΩ load resistance.

Design and simulation of MEMS piezoelectric vibration energy harvesters with centre mass block

MEMS-based piezoelectric vibration energy harvesters (MEMS-PVEHs) with center mass block are designed with the overall size 10 × 10 × 2 mm3, two prototypes including piezoelectric unimorph and bimorph beams are used respectively. This paper studies the characteristics of MEMS-PVEHs by modeling and simulation in COMSOL. Their eigenfrequencies are analyzed firstly, their optimal piezoelectric outputs are explored by changing excitation frequency and load resistance secondly, then the piezoelectric unimorph and bimorph beams are compared finally. The simulation results show that the optimal excitation frequency is slightly higher than the eigenfrequency, and the maximum piezoelectric power of the PVEH can be obtained only when the appropriate excitation frequency and load resistance are selected, and the power generation efficiency is 0.5. It has little difference between unimorph and bimorph to improve the MEMS-PVEH piezoelectric output. Finally, the piezoelectric unimorph with double opposite electrodes is designed based on the MEMS fabrication process.

Output Power of Piezoelectric MEMS Vibration Energy Harvesters Under Random Oscillation

The output characteristics of MEMS piezoelectric vibration energy harvesters (PVEHs) under random oscillations are analysed. We fabricated cantilever-type MEMS-PVEHs using Pb(Zr,Ti)O3 films. The autocorrelation function of the transient displacement of the cantilever tip under random oscillations features a narrow-band random vibration. From the power spectral density (PSD) of the output voltage of the PVEHs, the resonance frequency decreases and the full-width at half-maximum increases with increasing vibration acceleration. By comparing output properties under various sinusoidal oscillations, nonlinear effects including the soft-spring effect and nonlinear damping effect clearly influence the output characteristics under random oscillations. The power generation is proportional to the square of the vibration acceleration even in the acceleration region where nonlinear effects become conspicuous.

Enhancement of vibration based piezoelectric energy harvester using hybrid optimization techniques

MEMS unimorph piezoelectric vibration energy harvester is designed and optimized based on Hybrid Optimization techniques [genetic algorithm (GA), bat algorithm (BA), grey wolf optimization (GWO), hybrid bat algorithm tuned genetic algorithm (HBAGA) and hybrid grey wolf optimizer tuned genetic algorithm (HGWOGA)] for performance improvement. In this research work, unimorph piezoelectric vibration energy harvester is modeled using analytical equations, which is derived to determine the amount of voltage and power, harvested from the piezoelectric energy harvester. These derived analytical equations are used as the fitness function of Hybrid optimization techniques, which is a design optimization technique to improve the amount of power and voltage harvested from the unimorph piezoelectric energy harvester, by optimizing the parameters and a comparison is made within these techniques. The effects of geometry optimization on natural frequency and stress are also studied. The un-optimized results are compared with the optimized results (GA, BA, GWO, HBAGA and HGWOGA) and the results obtained, proves that, the optimized results are more efficient in all aspects, which has significantly improved the efficiency of the piezoelectric harvester to a larger extent. Finally, a comparison is made within the optimization techniques and HGWOGA has proved to be more efficient than HBAGA, GWO, BA, GA and this work of MEMS piezoelectric vibration energy harvester is simulated using the MATLAB software.

Design and Analysis of MEMS Based Aluminum Nitride (AlN), Lithium Niobate (LiNbO<sub>3</sub>) and Zinc Oxide (ZnO) Cantilever with Different Substrate Materials for Piezoelectric Vibration Energy Harvesters Using COMSOL Multiphysics Software

Interest in energy harvesters has grown rapidly over the last decade. The cantilever shaped piezoelectric energy harvesting beam is one of the most employed designs, due to its simplicity and flexibility for further performance enhancement. The research effort in the MEMS Piezoelectric vibration energy harvester designed using three types of cantilever materials, Lithium Niobate (LiNbO3), Aluminum Nitride (AlN) and Zinc Oxide (ZnO) with different substrate materials: aluminum, steel and silicon using COMSOL Multiphysics package were designed and analyzed. Voltage, mechanical power and electrical power versus frequency for different cantilever materials and substrates were modeled and simulated using Finite element method (FEM). The resonant frequencies of the LiNbO3/Al, AlN/Al and ZnO/Al systems were found to be 187.5 Hz, 279.5 Hz and 173.5 Hz, respectively. We found that ZnO/Al system yields optimum voltage and electrical power values of 8.2 V and 2.8 mW, respectively. For ZnO cantilever on aluminum, steel and silicon substrates, we found the resonant frequencies to be 173.5 Hz, 170 Hz and 175 Hz, respectively. Interestingly, ZnO/steel yields optimal voltage and electrical power values of 9.83 V and 4.02 mW, respectively. Furthermore, all systems were studied at different differentiate frequencies. We found that voltage and electrical power have increased as the acceleration has increased.

Design and Simulation of MEMS Piezoelectric Vibration Energy Harvesters with Center Mass Block

MEMS-based piezoelectric vibration energy harvesters (MEMS-PVEHs) with center mass block are designed with the overall size 10 × 10 × 2 mm3, two prototypes including piezoelectric unimorph and bimorph beams are used respectively. This paper studies the characteristics of MEMS-PVEHs by modeling and simulation in COMSOL. Their eigenfrequencies are analyzed firstly, their optimal piezoelectric outputs are explored by changing excitation frequency and load resistance secondly, then the piezoelectric unimorph and bimorph beams are compared finally. The simulation results show that the optimal excitation frequency is slightly higher than the eigenfrequency, and the maximum piezoelectric power of the PVEH can be obtained only when the appropriate excitation frequency and load resistance are selected, and the power generation efficiency is 0.5. It has little difference between unimorph and bimorph to improve the MEMS-PVEH piezoelectric output. Finally, the piezoelectric unimorph with double opposite electrodes is designed based on the MEMS fabrication process.

Harvesting the Ultimate Electrical Power From MEMS Piezoelectric Vibration Energy Harvesters: An Optimization Approach

Optimized MEMS piezoelectric vibration energy harvesters with maximum possible power generation have been proposed. The energy harvesters work based on the transduction of the applied vibration induced stress on the cantilever beams into the electrical power. Particle swarm optimization approach has been used to design the optimum unimorph and bimorph structures. The optimization has been done for different combinations of the top and bottom piezoelectric layers in bimorph energy harvesters. The geometries of the proposed structures and their harvested powers before and after the optimization have been calculated and compared. The optimization parameters have been chosen so that asymmetric structures with partial coverage of piezoelectric layers would be investigated. The results show that the proposed structures serve as the maximum power generators and provide the largest possible electrical power. In order to limit the beam free end displacement, a guided two beam design has been proposed and optimized. The proposed bimorph guided two beam energy harvester could achieve the minimum displacement which has a key effect on the lifetime of the energy harvesters.

Simulation study of MEMS piezoelectric vibration energy harvester based on c-axis tilted AlN thin film for performance improvement

In this paper, a MEMS piezoelectric cantilevered vibration energy harvester based on c-axis tilted AlN thin film is investigated. Based on basic piezoelectric equations and static analysis of cantilever beam, the equations for generated energy (E) and open circuit voltage (Vo) were derived, and simulations were carried out to study the effects of geometry parameters and c-axis tilted angle. Results show that E and Vo of energy harvesters are greatly dependent on c-axis tilted angle and geometry parameters, while the coupling between c-axis tilted angle and geometry parameters is not strong. For a given structure size, E and Vo can be almost simultaneously improved by controlling c-axis tilted angle; compared with the case of normal c-axis angle, E with optimal c-axis tilted angle can be amplified by more than 3 times, and the Vo is amplified by about 2 times. E or Vo could be further improved by geometry parameters, while there is trade-off between them. These results can be used for the design and application of piezoelectric cantilevered vibration energy harvester.

Cantilevers-on-membrane design for broadband MEMS piezoelectric vibration energy harvesting

Most MEMS piezoelectric vibration energy harvesters involve either cantilever-based topologies, doubly-clamped beams or membrane structures. While these traditional designs offer simplicity, their frequency response for broadband excitation are typically inadequate. This paper presents a new integrated cantilever-on-membrane design that attempts to both optimise the strain distribution on a piezoelectric membrane resonator and improve the power responsiveness of the harvester for broadband excitation. While a classic membrane-based resonator has the potential to theoretically offer wider operational frequency bandwidth than its cantilever counterpart, the addition of a centred proof mass neutralises its otherwise high strain energy regions. The proposed topology addresses this issue by relocating the proof mass onto subsidiary cantilevers and integrates the merits of both the membrane and the cantilever designs. When experimentally subjected to a band-limited white noise excitation, up to approximately two folds of power enhancement was observed for the new membrane harvester compared to a classic plain membrane device.

Five topologies of cantilever-based MEMS piezoelectric vibration energy harvesters: a numerical and experimental comparison

In the realm of MEMS piezoelectric vibration energy harvesters, cantilever-based designs are by far the most popular. For cantilever-based vibration energy harvesters, the active piezoelectric area near the clamped end is able to accumulate maximum strain-generated-electrical-charge, while the free end is used to house a proof mass to improve the power output without compromising the effective area of the piezoelectric generator since it experiences minimal strain anyway. However, despite while other contending designs do exist, this paper explores five selected micro-cantilever (MC) topologies, namely: a plain MC, a tapered MC, a lined MC, a holed MC and a coupled MC, in order to assess their relative performance as an energy harvester. Although a classical straight and plain MC offers the largest active piezoelectric area, alternative MC designs can potentially offer larger deflection and thus mechanical strain distribution for a given mechanical loading. Numerical simulation and experimental comparison of these 5 MCs (0.5 µm AlN on 10 µm Si) with the same practical dimensions of 500 µm and 2000 µm, suggest a cantilever with a coupled subsidiary cantilever yield the best power performance, closely followed by the classical plain cantilever topology.

Fabrication, Simulation and Characterisation of MEMS Piezoelectric Vibration Energy Harvester for Low Frequency

A MEMS vibration energy harvester using an Aluminium Nitride (AlN) piezoelectric layer was designed, fabricated and characterized. The harvester was fabricated on an SOI wafer with a 30μm device silicon layer which serves as the structural beam on which a 0.5μm AlN layer is sandwiched between the top and bottom electrodes. The handle silicon serves as the proof mass. The harvester has a measured resonant frequency of around 114Hz and an average output power of 54nW was measured at optimal load and a low level of acceleration (24 mili-g). A 3D finite element model of the harvester was created in COMSOL Multiphysics and the obtained results are in close agreement with the measured data.

Comparison of Five Topologies of Cantilever-based MEMS Piezoelectric Vibration Energy Harvesters

In the realm of MEMS piezoelectric vibration energy harvesters, cantilever-based designs are by far the most popular. Despite being deceptively simple, the active piezoelectric area near the clamped end is able to accumulate maximum strain-generated-electrical-charge, while the free end is able to accommodate a proof mass without compromising the effective area of the piezoelectric generator since it experiences minimal strain anyway. While other contending designs do exist, this paper investigates five micro-cantilever (MC) topologies, namely: a plain MC, a tapered MC, a lined MC, a holed MC and a coupled MC, in order to assess their relative performance as an energy harvester. Although a classical straight and plain MC offers the largest active piezoelectric area, alternative MC designs can potentially offer higher average mechanical strain distribution for a given mechanical loading. Numerical simulation and experimental comparison of these 5 MCs (0.5 μ AlN on 10 μm Si) with the same practical dimensions of 500 μm and 2000 μm, suggest a cantilever with a coupled subsidiary cantilever yield the best power performance, closely followed by the classical plain topology.

Analysis of Variable Section Piezoelectric Harvester

This paper first presents an analytical model for investigating the vibration performance of a thin curved laminated piezoelectric beam with variable curvatures and transverse sections. This kind of beam is widely used for the MEMS piezoelectric vibration energy harvester. The curved thin beam theory with bisymmetric section, here rectangular section used, is employed to explore the bending and twisting coupling vibration characteristics. In order to study the vibration properties with concentrated load, the effects of the tip proof mass isnt used. The paper also shows that the adoption of ANSYS software to carry out the MEMS piezoelectric vibration energy harvesters numerical simulation can improve the efficiency of the harvester designing and manufacturing consumedly. The results showed that the maximum voltage at the resonant point was increasing while the initial curvature radius increasing. On the other hand, the voltage difference of the inner edge and the outer edge was very small because the matrix layer was PDMS with very small stiffness and density.

Analysis of a Curved Beam MEMS Piezoelectric Vibration Energy Harvester

An analytical model is derived for obtaining the dynamic performance of a thin curved composite piezoelectric beam with variable curvatures for the MEMS piezoelectric vibration energy harvester. The plane curved beam theory with rectangular section is employed to explore the bending and twisting coupling vibration characteristics. In order to satisfy the most available environmental frequencies, which are on the order of 1000Hz, the parameters of the spiraled composite beam bonded with piezoelectric on the surfaces are investigated to provide a method of how to design low resonance beams while keeping the compacting structural assembly. The results indicate the adoption of ANSYS® software to carry out the MEMS piezoelectric vibration energy harvester’s numerical simulation can improve the accuracy of the harvester designing and manufacturing consumedly. And the simulation data also provide a theory analysis foundation for the engineering, design and application of harvester.

PERFORMANCE OF MICROFABRICATED PIEZOELECTRIC VIBRATION ENERGY HARVESTERS

ABSTRACT Model verification and design of MEMS piezoelectric vibration energy harvesters (MPVEH) are presented, motivated by lowering power requirements of wireless sensor nodes. Applications include structural health monitoring. Coupled electromechanical harvester models are presented and verified (through comparison with experimental data). Harvester material selection is discussed. The model is used to concurrently design a prototype MPVEH and a microfabrication scheme. Targeting low-level (2.5 m/s2), low-frequency (150 Hz) vibrations, power density (310 μW/cm3) and voltage (0.4 V p−p ) are predicted. Methodologies for scalar analysis and optimization of harvesters are presented with a scheme for chip-level assembly of harvester clusters to meet node requirements. **Currently Doctoral candidate at California Institute of Technology, Department of Mechanical Engineering. ***Boeing Assistant Professor.