Ambient Mechanical Vibrations Research Articles

Instrumented indentation of PMMA/ZnO nanocomposites films

Piezoelectric nanocomposite films comprise zinc oxide (ZnO) nanoparticles as reinforcement and poly-methyl methacrylate (PMMA) as the matrix. These films can potentially be used as structural and functional components of microdevices that can harvest energy from ambient mechanical vibrations. The design of such energy-scavenging micro/nano-systems will require knowledge of the process-microstructure-property relationships of nanocomposite films. This study synthesized PMMA/ZnO nanocomposite films using ultrasonic probe sonication and solution-casting. The nanomechanical characterization of the nanocomposite films was conducted using a nanoindenter via quasi-static mode. Quasi-static nanoindentation revealed that the indentation modulus ranged from 3.49 ± 0.03 GPa for PMMA to 4.71 ± 0.07 GPa for PMMA/ZnO 5 wt% nanocomposite film. However, the indentation modulus of 10 wt% ZnO nanocomposites decreases, i.e. 4.22 ± 0.60 GPa. The indentation hardness varied from 311.97 ± 6 MPa for PMMA thermoplastic polymer to 432.94 ± 83.81 MPa for PMMA/ZnO 10 wt% nanocomposites film. In addition, the properties of the nanocomposite film vary, as supported by scanning electron micrographs.

Piezoelectric Energy Harvester Technologies: Synthesis, Mechanisms, and Multifunctional Applications.

Piezoelectric energy harvesters have gained significant attention in recent years due to their ability to convert ambient mechanical vibrations into electrical energy, which opens up new possibilities for environmental monitoring, asset tracking, portable technologies and powering remote "Internet of Things (IoT)" nodes and sensors. This review explores various aspects of piezoelectric energy harvesters, discussing the structural designs and fabrication techniques including inorganic-based energy harvesters (i.e., piezoelectric ceramics and ZnO nanostructures) and organic-based energy harvesters (i.e., polyvinylidene difluoride (PVDF) and its copolymers). The factors affecting the performance and several strategies to improve the efficiency of devices have been also explored. In addition, this review also demonstrated the progress in flexible energy harvesters with integration of flexibility and stretchability for next-generation wearable technologies used for body motion and health monitoring devices. The applications of the above devices to harvest various forms of mechanical energy are explored, as well as the discussion on perspectives and challenges in this field.

One-dimensional KNN micro rods doping to facilitate the energy conversion performance of a KNN MRs/P(VDF-TrFE) composite

Piezoelectric self-powered electronic devices can convert ambient mechanical vibrations into electrical energy in an environmentally friendly manner, significantly alleviating the scarcity of non-renewable sources. This work prepares an one-dimensional potassium sodium niobate micro rods (1D KNN MRs) using the molten salt - topological chemical reaction method, showing the significant advantages over 0-dimension (0D) nanoparticles due to its anisotropy. Simultaneously, KNN MRs are introduced into poly (vinylidene fluoride-trifluoroethylene) to form a KNN MRs/P(VDF-TrFE) piezoelectric composite, effectively facilitating the piezoelectric β-phase in P(VDF-TrFE) film, and contributing to a high remnant polarization (Pr ∼12.3 μC/cm2) at 125 MV/m and a high piezoelectric constant (d33 = −28 pC/N). Interestingly, a piezoelectric sensor assembled by KNN MRs/P(VDF-TrFE) composite shows a considerable piezoelectric output of 17.6 V at a scene of 2.5 MPa stress, offering a novel route for designing the optimum ceramic/polymer combinations suitable for mechanical energy conversion and energy harvesting.

Investigative Study of the Effect of Damping and Stiffness Nonlinearities on an Electromagnetic Energy Harvester at Low-Frequency Excitations

Ambient vibration energy is widely being harnessed as a source of electrical energy to drive low-power devices. The vibration energy harvester (VEH) of interest employs an electromagnetic transduction mechanism, whereby ambient mechanical vibration is converted to electrical energy. The limitations affecting the performance of VEHs, with an electromagnetic transduction structure, include its operational bandwidth as well as the enclosure-size constraint. In this study, an analysis and design of a nonlinear VEH system is conducted using the Output Frequency Response Function (OFRF) representations of the actual system model. However, the OFRF representations are determined from the Generalised Associated Linear Equation (GALE) decompositions of the system of interest. The effect of both nonlinear damping and stiffness characteristics, to, respectively, extend the average power and operational bandwidth of the VEH device, is demonstrated.

Adaptive energy harvesting from low-level ambient vibrations

Harvesting energy from ambient mechanical vibrations is an enabling technology with profound societal impacts. However, existing methods suffer from two major technical deficiencies: the weak coupling between the harvester and the vibrating source and the low energy transduction efficiency. Here we show an adaptive approach can overcome these challenges, leading to improvements by orders of magnitude. Using a piezoelectric device, we demonstrate that a conservative actuation force can block energy from flowing back to the vibrating source, thereby increasing the coupling strength and increasing the transduction efficiency significantly. Using low actuation forces, the adaptive approach can extract almost two orders of magnitude more power than the traditional approach from a multi-frequency vibration. The improvement can increase to three orders of magnitude when moderate actuation force is used. If materials that can withstand a high actuation voltage are available, the adaptive approach has the potential to surpass the theoretical performance ceiling of the traditional approach, improving the upper-bound performance by over 100 times and creating a significant opportunity for the technology to advance.

Frequency domain analysis of a piezoelectric energy harvester with impedance matching network

Abstract Piezoelectric energy harvesters are electromechanical systems, capable to convert ambient dispersed mechanical vibrations into usable electrical energy. They can be used for supplying power to sensors and actuators that are wireless connected, miniaturized and remote located. In this work, we analyze piezoelectric energy harvesters for mechanical vibrations in the frequency domain. White Gaussian and colored noise models for random vibrations are considered. The governing equations for the harvester are derived from mechanical properties, the characteristic relationships of piezoelectric materials, and circuit description of the electrical load. We show that the energy harvester can be modelled by cascade connected electromechanical two-ports, and that frequency domain methods are the perfect tool for analysis. Formulas for the harvested power and power efficiency are derived. We also show that application of matching networks reduces the impedance mismatch between the mechanical and the electrical parts, significantly increasing the harvested power and power efficiency. The matching network solution is compared to others, previously proposed solutions, such as application of power-factor correction. We show that the matching network offers nine times more average power and better power efficiency than the unmatched resistive load, and increases by more than 10% the harvested power and efficiency, with respect to the power-factor corrected solution.

Design, modeling, and frequency domain analysis with parametric variation for fixed-guided vibrational piezoelectric energy harvesters

The aim of the presented work is to design, model, and analyze the fixed-guided two-beam (FG2B) & fixed-guided four-beam (FG4B) piezoelectric energy harvesters, especially for ambient mechanical energy harvesting applications. Two and four rectangular beams are connected at the middle of the square-shaped seismic-mass in these configurations. The performance of the energy harvesters is analyzed using eigen-mode analysis and frequency domain analysis. To determine the resonance frequency of the energy harvesters the eigen-mode analysis is performed. The frequency domain analysis is coupled with parametric sweep analysis to analyze the effect of variation in input acceleration from 1g to 5g (g=9.8m/s2) on von Mises stress, displacement, electric potential, and output electric power. The main aim of the energy harvester is to generate electric power from the ambient mechanical vibrations. The reported FG2B and FG4B energy harvester produce an optimum electric output power of 0.55µW and 0.25µW at the maximum load resistance of 0.52MΩ and 0.2MΩ, respectively, with the electric potential of 0.8V and 0.32V respectively. Hence, the proposed energy harvesters generate higher electric potential and output power at a higher resistive load range with less device volume than the work reported in the literature. The designed energy harvesters resonate at around 550 Hz and 770 Hz for FG2B and FG4B respectively, which is in the low-frequency range and hence can be efficiently utilized for low-frequency energy harvesting applications with better electrical output power.

On the Efficiency Enhancement of an Actively Tunable MEMS Energy Harvesting Device

In this paper, we propose an active control method to adjust the resonance frequency of a capacitive energy harvester. To this end, the resonance frequency of the harvester is tuned using an electrostatic force, which is actively controlled by a voltage source. The spring softening effect of the electrostatic force is used to accommodate the dominant frequency of the ambient mechanical vibration within the bandwidth of the resonance region. A single degree of freedom is considered, and the nonlinear equation of motion is numerically integrated over time. Using a conventional proportional–integral–derivative (PID) control mechanism, the results demonstrated that our controller could shift the resonance frequency leftward on the frequency domain and, as a result, improve the efficiency of the energy harvester, provided that the excitation frequency is lower than the resonance frequency of the energy harvester. Application of the PID controller in the resonance zone resulted in pull-in instability, adversely affecting the harvester’s performance. To tackle this problem, we embedded a saturation mechanism in the path of the control signal to prevent a sudden change in motion amplitude. Outside the pull-in band, the saturation of the control signal resulted in the reduction of harvested power compared to the non-saturated signal; this is a promising improvement in the design and analysis of energy harvesting devices.

An Impedance Matching Solution to Increase the Harvested Power and Efficiency of Nonlinear Piezoelectric Energy Harvesters

Circuit theory and nonlinear dynamics are instrumental to design efficient energy harvesters for ambient mechanical vibrations. In this work, we show that an impedance matching networks can be designed that maximizes the harvested power, and improves the power efficiency. The proposed matching network achieves impedance matching at a single frequency, that can be chosen at will by the designer, and does not need to coincide with the resonant frequency of the harvester. Moreover, the matching network also increases the harvested power over a wide frequency bandwidth. According to our numerical simulations, the matching network increases the maximum harvested power by a factor greater than 3, and the power harvested over the whole frequency spectrum by a factor of 6. The frequency bandwidth can be further extended considering nonlinear energy harvesters. Even using the matching network designed for the linear case, performance is significantly nonetheless improved for the nonlinear harvester.

Geometrical Investigation of Piezoelectric Patches for Broadband Energy Harvesting in Non-Deterministic Composite Plates.

Mechanical energy is the most ubiquitous form of energy that can be harvested and converted into useful electrical power. For this reason, the piezoelectric energy harvesters (PEHs), with their inherent electromechanical coupling and high-power density, have been widely incorporated in many applications to generate power from ambient mechanical vibrations. However, one of the main challenges to the wider adoption of PEHs is how to optimize their design for maximum energy harvesting. In this paper, an investigation was conducted on the energy harvesting from seven piezoelectric patch shapes (differing in the number of edges) when attached to a non-deterministic laminated composite (single/double lamina) plate subjected to change in fiber orientation. The performance of the PEHs was examined through a coupled-field finite element (FE) model. The plate was simply supported, and its dynamics were randomized by attaching randomly distributed point masses on the plate surface in addition to applying randomly located time-harmonic point forces. The randomization of point masses and point force location on a thin plate produce non-deterministic response. The design optimization was performed by employing the ensemble-responses of the electrical potential developed across the electrodes of the piezoelectric patches. The results present the optimal fiber orientation and patch shape for maximum energy harvesting in the case of single and double lamina composite plates. The results show that the performance is optimal at 0° or 90° fiber orientation for single-lamina, and at 0°/0° and 0°/90° fiber orientations for double-lamina composites. For frequencies below 25 Hz, patches with a low number of edges exhibited a higher harvesting performance (triangular for single-lamina/quadrilateral for double-lamina). As for the broadband frequencies (above 25 Hz), the performance was optimal for the patches with a higher number of edges (dodecagonal for single-lamina/octagonal for double-lamina).

A Self-Powered and Battery-Free Vibrational Energy to Time Converter for Wireless Vibration Monitoring

Wireless sensor nodes (WSNs) are the fundamental part of an Internet of Things (IoT) system for detecting and transmitting data to a master node for processing. Several research studies reveal that one of the disadvantages of conventional, battery-powered WSNs, however, is that they typically require periodic maintenance. This paper aims to contribute to existing research studies on this issue by exploring a new energy-autonomous and battery-free WSN concept for monitor vibrations. The node is self-powered from the conversion of ambient mechanical vibration energy into electrical energy through a piezoelectric transducer implemented with lead-free lithium niobate piezoelectric material to also explore solutions that go towards a greener and more sustainable IoT. Instead of implementing any particular sensors, the vibration measurement system exploits the proportionality between the mechanical power generated by a piezoelectric transducer and the time taken to store it as electrical energy in a capacitor. This helps reduce the component count with respect to conventional WSNs, as well as energy consumption and production costs, while optimizing the overall node size and weight. The readout is therefore a function of the time it takes for the energy storage capacitor to charge between two constant voltage levels. The result of this work is a system that includes a specially designed lead-free piezoelectric vibrational transducer and a battery-less sensor platform with Bluetooth low energy (BLE) connectivity. The system can harvest energy in the acceleration range [0.5 g–1.2 g] and measure vibrations with a limit of detection (LoD) of 0.6 g.

Piezoelectric Energy Harvesting Methodologies using Ambient Mechanical Vibration: Design Perspective and Challenges

Background and Objective: Piezoelectric energy harvesting is an emergent research area for unobtrusive power supply for fully autonomous micro-scale devices. Method: The method of energy harvesting is to utilize waste ambient mechanical vibrations to generate electrical energy through the piezoelectric effect. Results and Conclusion: The present work highlights the major advances made in the field of micro- electromechanical systems based on piezoelectric energy harvester on extracting ambient vibrations and converting them into usable electric power. The present study explores energy harvesting approaches for portable electronics and self-powered wireless network nodes. The performance matrices like device physics, volume, operating frequencies, design and materials have been thoroughly analyzed in this work. Conventional cantilever fabrication steps have also been discussed. Finally, guidelines for future research and performance enhancements in the field of Piezoelectric Energy Harvesting (PEH) at micro scale have been discussed.

Development and experimental validation of self-powered wireless vibration sensor node using vibration energy harvester

This paper deals with development of a self-powered solution for wireless vibration sensing. An autonomous operation of the proposed vibration sensor node is based on an electromagnetic energy harvesting device which converts kinetic energy of ambient mechanical vibration. Moreover, mechanical vibrations are monitored via electric signal from a piezoelectric patch and the measured signal is transmitted to the monitoring unit. The electromagnetic energy harvester is designed to provide enough power for a signal processing unit and a communication module, enabling the system to operate as a self-powered wireless vibration sensor node. Operation of this system was experimentally validated in laboratory environment and examples of vibration monitoring are presented. There is a significant restriction in terms of operation in resonance regime, where the generated power of the kinetic energy harvester is maximal and sufficient for limitless operation of the node. Main aim of this paper is to present a complex system which could be used in many engineering applications, such as aerospace, transportation, or civil structure monitoring.

A facile and robust route to polyvinyl alcohol-based triboelectric nanogenerator containing flame-retardant polyelectrolyte with improved output performance and fire safety

Abstract Harvesting energy from various ambient mechanical vibrations and motions is a promising green technology to provide electrical power for integrated electronic devices or sensors. However, some applications of the triboelectric nanogenerators (TENGs) in harsh environment faces challenges of fire safety. Herein, we proposed a facile, robust, and low-cost solution-casting method to prepare flame-resistant triboelectric polymer of polyvinyl alcohol (PVA) by doping PPA-PEI polyelectrolyte synthesized from phenyl phosphonic acid and branched polyethyleneimine. The PVA/PPA-PEI film containing 10 wt% PPA-PEI not only self-extinguished immediately after the burner moved away while the neat PVA film burned thoroughly, but also showed the minimum peak heat release rate (PHRR) of 148.7 ± 4.2 W/g with a reduction of ~ 47.8%. Contributed by the hybrid of electron and ion transfer on the triboelectric layers during the electrification process, the resultant PVA/10 wt% PPA-PEI: PVDF flame-retarding TENG also exhibited the maximum open-circuit voltage of 28.8 ± 0.4 V, short-circuit current of 62.3 ± 5.4 μA, and power of 228.8 μW, which were respectively 50.0%, 170.0%, and 57.4% higher than those of the pristine PVA: PVDF TENG when mechanically excited by a dynamic mechanical analyzer (DMA) working at 2000 µm and 10 Hz. The incorporation of flame-retardant polyelectrolyte into common polymers provides a promising pathway to make traditional TENGs with both enhanced flame retardancy and electrical output.

Electromechanical Modeling of Vibration-Based Piezoelectric Nanogenerator with Multilayered Cross-Section for Low-Power Consumption Devices

Piezoelectric nanogenerators can convert energy from ambient vibrations into electrical energy. In the future, these nanogenerators could substitute conventional electrochemical batteries to supply electrical energy to consumer electronics. The optimal design of nanogenerators is fundamental in order to achieve their best electromechanical behavior. We present the analytical electromechanical modeling of a vibration-based piezoelectric nanogenerator composed of a double-clamped beam with five multilayered cross-sections. This nanogenerator design has a central seismic mass (910 μm thickness) and substrate (125 μm thickness) of polyethylene terephthalate (PET) as well as a zinc oxide film (100 nm thickness) at the bottom of each end. The zinc oxide (ZnO) films have two aluminum electrodes (100 nm thickness) through which the generated electrical energy is extracted. The analytical electromechanical modeling is based on the Rayleigh method, Euler–Bernoulli beam theory and Macaulay method. In addition, finite element method (FEM) models are developed to estimate the electromechanical behavior of the nanogenerator. These FEM models consider air damping at atmospheric pressure and optimum load resistance. The analytical modeling results agree well with respect to those of FEM models. For applications under accelerations in y-direction of 2.50 m/s2 and an optimal load resistance of 32,458 Ω, the maximum output power and output power density of the nanogenerator at resonance (119.9 Hz) are 50.44 μW and 82.36 W/m3, respectively. This nanogenerator could be used to convert the ambient mechanical vibrations into electrical energy and supply low-power consumption devices.

Simulation of Synchronized-Switching Method Energy Harvester Including Accurate Piezoceramic Nonlinear Behavior

Synchronized-switching techniques have significantly enhanced the harvested energy from semipassive and active surrounding ambient mechanical vibration harvesters. They have allowed a large improvement of vibration-control efficiency using piezoelectric devices. Unfortunately, for such techniques, dielectric limitations appear as soon as the piezoceramic operates under external solicitation of higher amplitudes and frequencies. Under extreme conditions, active materials exhibit nonlinear behavior related to dielectric hysteresis that significantly reduces their performance. In this work, we focus on this nonlinear behavior and its consequences in terms of system efficiency. We apply a realistic model including accurate material laws. In such models, a constant piezoelectric coupling d 31 is not suitable as a coefficient anymore and it should be replaced by a function depending on the polarization level through the active material. The response of more realistic systems including hysteresis was taken into account and compared with the basic model, where a constant d 31 was considered.

Energy Harvesting Using a Torsional Mode L-Shaped Unimorph Structure: Modeling and Experimental Investigations

Abstract Previous studies have proved that the piezoelectric L-shaped beam-mass structure is a good candidate to harvest energy from ambient mechanical vibration. However, most researches merely focused on bending mode of the structure, which only can capture energy from in-plane base excitation. To fully exert the advantages of L-shaped harvesters, this paper will explore their energy harvesting performance on torsional mode with out-of-plane base excitation. The electromechanical coupling governing equation of the L-shaped harvester in torsional mode is derived by applying Gauss's law and the Euler–Bernoulli beam theory with linear assumption, and the analytical results are also validated with experimental results. In addition, the influences of key geometric parameters on the resonance frequency and output voltage of the harvester are also presented. This work demonstrates the feasibility of utilizing torsional mode of the L-shaped unimorph structure to harvest energy from out-of-plane mechanical vibration, which shows the potential of designing multi-directional and multi-frequency L-shaped harvesters.

Broadband, Tunable, Miniaturized Vibration Energy Harvester Using Nonlinear Elastomer Beams and Stretchable Interconnects

AbstractA miniaturized vibration energy harvester, a small yet sustainable power source that converts ambient mechanical vibration into electricity, is considered as a key technology to advance wireless sensor networks for the internet of things. Conventional chip‐scale vibration energy harvesters, such as microelectromechanical systems devices that are mostly based on rigid materials (e.g., silicon), inherently exhibit high resonant frequency, narrow bandwidth, and a single peak frequency. Therefore, they are often unsuitable for many real‐life applications, as most ambient vibrations have low frequency, broad spectrum, and time variant resonance. Here, an unconventional, soft‐rigid hybrid architecture for vibration energy harvesting, which is inspired by soft electronics, is presented to overcome these limitations. By harnessing soft materials undergoing large deformation, the reported device is designed and tested to demonstrate its energy harvesting performance with high miniaturization, low operation frequency, broadband spectrum, and resonant frequency tuning.

Analysis of bimorph piezoelectric beam energy harvesters using superconvergent element

Cantilever-based piezoelectric energy harvesters have been utilized as structures to extract mechanical energy from the ambient mechanical vibrations and transfer it into the electrical output. In this article, the performance of bimorph piezoelectric beam energy harvesters is investigated. The cantilever beam is modeled by using both Timoshenko and Euler–Bernoulli beam theories. The equations are discretized using the conventional finite element method and superconvergent element. Besides the high rate of convergence, easy switching between the above beam theories is enabled by such type of element. The current model is presented for a Timoshenko beam model, but it could as well be used for a Euler–Bernoulli beam model. In addition, voltage, current, and power frequency response functions for different ranges of load resistance varying from the short-circuit to open-circuit conditions are determined to reach the maximum values. Effects of the slenderness ratio and the required beam model based on the geometric properties of the piezoelectric energy harvesters are discussed in the final part of this study. The results show that only for smaller values of the slenderness ratio (below 5), it is necessary to model the beam using the Timoshenko assumptions; otherwise both beam theories provide approximately the same responses.

Analysis, Design, and Implementation of an Elastomer Generator Based Energy Harvesting Scheme

Dielectric elastomer generator (DEG) is a special variable capacitor generator used to harvest electrical energy from ambient mechanical vibrations, such as waves, building vibrations, wind, and human movement. The DEG, by virtue of its variable capacitance, converts the applied mechanical energy into electrical form. For successful energy harvesting, the DEG requires controlled charging and discharging operations. Thus, the energy harvesting circuits, used to charge and discharge the DEG, must work in tandem with the mechanical vibrations. The energy harvested during a single cycle of DEG operation increases with an increase in the DEG operating voltage. Hence, energy harvesting circuits must drive the DEG at high voltage levels. These two requirements make the energy harvesting circuit design a challenging job. In this paper, a novel energy harvesting system is proposed to drive the DEG without needing a position sensor, a high-voltage source, or a high turns ratio transformer. The theory of the proposed scheme is explained and validated with experiments performed on a prototype DEG. The control implemented leads to a special intermittent operation of the energy recovery circuit, which is also introduced. 2.597 mJ energy was harvested from a single elastomer film of 10 cm diameter with 2.3 nF capacitance in relaxed condition.