MEMS Piezoelectric Energy Harvester Research Articles

Piezoelectric MEMS Energy Harvester for Low-Power Applications

Piezoelectric MEMS Energy Harvester for Low-Power Applications

FEM-Inclusive Transfer Learning for Bistable Piezoelectric MEMS Energy Harvester Design

In this article, a bistable piezoelectric MEMS energy harvester is presented to operate in a low-frequency range, around 100–200 Hz. The proposed design has an M-shaped structure with a couple of proof masses to not only lower the operating frequencies but also enlarge the frequency bandwidth. This specific structure has multidegrees of freedom, making it fit for a bistable piezoelectric energy harvester on the MEMS scale. An artificial neural network (ANN) is used to tackle this design in order to facilitate the optimization process and determine proper physical dimensions. To improve the accuracy and boost the training process of deep neural network (DNN), we utilize a transfer learning technique in this work. The analytical modeling and finite-element modeling (FEM) simulation data have been used for the DNN model training. Here, a DNN is first trained with a large dataset computed from the lumped-parameter model, and then, the trained network is transferred to a new DNN model for another round of training with a small dataset of highly accurate FEM simulation data samples to further reduce the estimation error. It is shown that the new model can estimate the device features with over 94% accuracy, which is considerably higher than the regular DNN. Next, the trained model is used as a performance estimator in a genetic algorithm (GA) to optimize the topology of the device to improve the operating frequency range and the generated voltage. An optimized design with a total volume of 1.02 mm3 was fabricated by the micromachining process. Our experimental results confirm that the proposed transfer-learning-based method can not only reduce the prototype’s first and second resonant frequencies to 123.8 and 175.7 Hz, respectively, but also enhance the generated power up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2.83 ~\mu \text{W}$ </tex-math></inline-formula> under 0.2-g input acceleration.

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.

Piezoelectric MEMS Energy Harvester from Airflow at Low Flow Velocities

Piezoelectric MEMS Energy Harvester from Airflow at Low Flow Velocities

Broadband Zero-Power Wakeup MEMS Device for Energy-Efficient Sensor Nodes.

A zero-power wakeup scheme for energy-efficient sensor applications is presented in this study based on a piezoelectric MEMS energy harvester featuring wafer-level-integrated micromagnets. The proposed setup overcomes a hybrid assembly of magnets on a chip-level, a major drawback of similar existing solutions. The wakeup device can be excited at low frequencies by frequency up-conversion, both in mechanical contact and contactless methods due to magnetic force coupling, allowing various application scenarios. In a discrete circuit, a wakeup within 30–50 ms is realized in frequency up-conversion at excitation frequencies < 50 Hz. A power loss in the off state of 0.1 nW renders the scheme virtually lossless. The potential extension of battery lifetime compared to cyclical wakeup schemes is discussed for a typical wireless sensor node configuration.

Deep-Learning-Based Optimization for a Low-Frequency Piezoelectric MEMS Energy Harvester

High operational frequency is one of the major limitations of the conventional MEMS vibration energy harvesters. In this work, we present a piezoelectric MEMS energy harvester with the capability of operating at a low resonant frequency (i.e., less than 200 Hz). The proposed harvester has a symmetric serpentine structure with a doubly clamped configuration comprising several proof masses at the junctions. In order to facilitate the design process and determine the optimum physical dimensions, an artificial neural network is used to model the design. In the first step, a dataset with 108 samples is generated by finite element modeling (FEM) to train a deep neural network. The validation results indicate that the trained deep neural network model can achieve around 90% estimation accuracy of device features, such as resonant frequency and harvested voltage. Next, this trained model is integrated with genetic algorithm as a performance estimator to optimize the geometry of the harvester to lower the resonant frequency and improve the harvested voltage. An optimized harvester with a total area of 8.7 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> has been fabricated through a standard micromachining process. Our measurement results confirm that the proposed deep-learning-based method can help reach the balanced summit of both higher power density and lower resonant frequency among the published works. Our prototype device features the first resonant frequency of 121.7 Hz and the harvested power of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.73~\mu \text{W}$ </tex-math></inline-formula> under 0.1g input acceleration.

Artificial Intelligence-Based Optimization of a Bimorph-Segmented Tapered Piezoelectric MEMS Energy Harvester for Multimode Operation

This paper presents a study on the design and multiobjective optimization of a bimorph-segmented linearly tapered piezoelectric harvester for low-frequency and multimode vibration energy harvesting. The procedure starts with a significant number of FEM simulations of the structure with different geometric dimensions—length, width, and tapering ratio. The datasets train the artificial neural network (ANN) that provides the fitting function to be modified and used in algorithms for optimization, aiming to achieve minimal resonant frequency and maximal generated power. Levenberg–Marquardt (LM) and scaled conjugate gradient (SCG) methods were used to train the ANN, then the goal attainment method (GAM) and genetic algorithm (GA) were used for optimization. The dominant solution resulted from optimization by the genetic algorithm integrated with the ANN fitting function obtained by the SCG training method. The optimal piezoelectric harvester is 121.3 mm long and 71.56 mm wide and has a taper ratio of 0.7682. It ensures over five times greater output power at frequencies below 200 Hz, which benefits the low frequency of the vibration spectrum. The optimized design can harness the power of higher-resonance modes for multimode applications.

Design and Performance of ScAlN/AlN Trapezoidal Cantilever-Based MEMS Piezoelectric Energy Harvesters

In this work, we report a method to enlarge the trapezoidal cantilever-based harvester power by using the high-performance Sc <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.2</sub> Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.8</sub> N/aluminum nitride (AlN) composite film and introducing symmetrical corners to both sides of the beam. Energy harvesters with variable beam structure and piezoelectric film are designed and evaluated by simulations and experiments. The trapezoid with corners (TWCs) cantilever is verified to improve the output power by a factor of five times when compared with the conventional trapezoidal cantilever without corners. The maximum power density of the ScAlN/AlN-based TWC cantilever harvester is about twice that of the AlN-based harvester, reaching 2.054 mW ·g <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> ·cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> at a frequency of 330.25 Hz. The optimization of piezoelectric film and structure can give an inspiration for further improving the performance of cantilever-based energy harvesters.

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 Lead-Free Spiral Bimorph Piezoelectric MEMS Energy Harvester for Enhanced Power Density

Tiny sensor nodes are the demand of smart and intelligent systems. These sensor nodes require on-board self-powered generating systems. Also, such generators should have lesser size. MEMS energy harvesters are profoundly used as the on-board self-powered generators. However, the size constrain imposes an important design trade-off on such devices. This trade-off is in-between areal dimension and the resonant frequency. In this paper, we have proposed an efficient bimorph energy harvester design which produces higher power density at very low resonance frequency. We have considered the poisonous behavior of lead-based devices as well and proposed lead-free designs in our work. The proposed design consists of a bimorph square plate of 2.25 mm2 with two Zinc Oxide (ZnO) layers of 0.5 µm each sandwiched a copper electrode layer of 1 µm. A spiral cut of 5 µm thickness is made over the plate in order to form a fixed free beam structure. Furthermore, without the inclusion of tip mass, the resonant frequency of the beam is controlled by varying the number of spiral turns. Our proposed design outperformed the previous designs by producing maximum output power of 15 nW at 110 Hz with seven spiral turns with very lower active volume. Also, it has a normalized volumetric power density of 3 × 10−2 µW/mm3 g2 Hz.

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.

Two-degree-of-freedom Piezoelectric MEMS Energy Harvester Based on Bulk PZT Film

Two-degree-of-freedom Piezoelectric MEMS Energy Harvester Based on Bulk PZT Film

An Autonomous Interface Circuit Based on Self-Investing Synchronous Energy Extraction for Low Power Piezoelectric Energy Harvesters

This paper presents a self-powered interface circuit to rectify and manage the AC output of the piezoelectric energy harvesters (PEH) by utilizing Self-Investing Synchronous Electric Charge Extraction technique (SI-SECE). The system invests charges from the battery to PEH to improve the electromechanical coupling factor and consequently the energy extraction by utilizing only one external component. The circuit was implemented in 180 nm CMOS technology where high voltage (HV) MOS transistors are utilized to tolerate high open circuit output voltages of PEHs. MEMS PEH with 4.7 nF inherent capacitance has been used to charge a 1 μF storage capacitor. Proposed interface circuit extracts 18.55 μW that is 33 % more than traditional SECE (13.95 μW) for 250 Hz PEH excitation frequency and 2.3 V piezoelectric open circuit voltage amplitude. At the output power of 48.5 μW, maximum power conversion efficiency of 62.4% is achieved as charge investment and corresponding conduction and switching losses on investing transistors. SI-SECE delivers power with 4.5x relative performance improvement over on-chip full-bridge rectifier.

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.

MEMS Energy Harvesting Based on Uniform-Stress Cantilever with Multilayer PZT Thin Films

Multilayered piezoelectric MEMS energy harvesters based on sputtering depositions are designed and fabricated. To obtain high endurance and output power, the unimorph cantilever structure with totally 10 μm-thick multilayered PZT thin films and 80 μm-thick Si elastic layer is designed. In addition, the cantilever is designed to undergo a uniform stress on the PZT. The output power and voltage was 90 μW and 1.0 Vrms under the input acceleration of approximately 1.2 G (=11.76 m/s2) and optimum load resistance.

A Nail-Size Piezoelectric Energy Harvesting System Integrating a MEMS Transducer and a CMOS SSHI Circuit

Piezoelectric vibration energy harvesting has drawn much interest to power distributed wireless sensor nodes for Internet of Things (IoT) applications where ambient kinetic energy is available. For certain applications, the harvesting system should be small and able to generate sufficient output power. Standard rectification topologies such as the full-bridge rectifier are typically inefficient when adapted to power conditioning from miniaturized harvesters. Therefore, active rectification circuits have been researched to improve overall power conversion efficiency, and meet both the output power and miniaturization requirements while employing a MEMS harvester. In this paper, a MEMS piezoelectric energy harvester is designed and co-integrated with an active synchronized switch harvesting on inductor (SSHI) rectification circuit designed in a CMOS process to achieve high output power for system miniaturization. The system is fully integrated on a nail-size board, which is ready to provide a stable DC power for low-power mini sensors. A MEMS energy harvester of 0.005 cm3 size, co-integrated with the CMOS conditioning circuit, outputs a peak rectified DC power of 40.6 $\mu \text{W}$ and achieves a record DC power density of 8.12 mW/cm3 when compared to state-of-the-art harvesters.

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&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt;) 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.