Piezoelectric Power Research Articles

Controlling ZnO Nanosheet Morphology By Galvanostatic Electrodeposition

Functionalizing nanostructure material is essential in future technology development. ZnO nanosheet is one type of metal oxide nanomaterials with its unique structures utilized in many devices, such as dye sensitized solar cell1,2,3, gas sensor4, photodetector4,5, and piezoelectric power generator6. Controlling ZnO nanosheet morphology in terms of its height, density, porous structure, etc. thus is of importance matter to improve the performance of the devices. Deposition of ZnO nanosheet on conductive substrate by electrochemical method offers a simple way to get excellent material-to-substrate attachment which ensure good electron transport needed for electronic devices. Generally the electrochemical deposition have been conducted in the potentiostatic mode1,2but not galvanostatic because it is considered that the potential decides the deposition reaction. However, for such an insulating nanostructure, it is difficult to directly relate the reaction to the electrode potential. On the other hand, the galvanostatic electrodeposition, that is convenient by using two electrodes system, can give better control over the constant crystal growth rate due to the external current responsible for the growth being always supplied in the constant manner throughout deposition, regardless the changes of the structure. In this report, galvanostatic electrodeposition of ZnO nanosheet on FTO or ITO substrate is studied to reveal important parameters responsible for controlling its morphology. The Acetate ion was used as the additive in the Zinc-Nitrate-based electrolyte solution in this study. Several key parameters such as applied current density, deposition time and temperature were varied, and the effect to the crystal growth and morphological changes was observed. XRD, SEM and TG/DTA were used to analyze the ZnO crystal growth mechanism, morphological changes and phase transformation during annealing process, respectively. It was found that both ZnO and Zn5(CH3COO)2(OH)8·2H2O crystals were observed in the as-deposited samples, which were then completely transformed to ZnO after annealing at 400 oC for 1 hour. Zn5(CH3COO)2(OH)8·2H2O is a side product produced due to the presence of Acetate ion, in which the anion’s main role is to inhibit ZnO preferential growth at (002) direction thus produce the desired nanosheet structure as the result. The effect of deposition time on the morphology was examined by varying the deposition time from 1, 5, 30 and 60 minutes with the current density and deposition temperature held constant at –1 mA/cm2 and 60 oC, respectively. Increasing deposition time was found to increase in nanosheet’s height and density, but further prolonging will promote growth of dense layer at the bottom part of the nanosheet. To observe the effect of applied current density, deposition time and temperature were held constant at 5 minutes and 60 oC respectively, with the current density varied from –1, –3 and –5.3 mA/cm2. Increasing applied current is found to be effective in increasing nanosheet’s height and density without producing the extra bottom layer. The deposition temperature was varied from 50, 60 and 70 oC under the same applied current density and deposition time, –1 mA/cm2and 5 minutes, respectively. The results indicate that the morphology is not sensitive to the temperature change in the range. In this report, optimization strategy to control the ZnO nanosheet morphology and complete explanation of the crystal growth mechanism will be presented and discussed. References Prog. Photovolt: Res. Appl., 2014, 22:440–451 ACS Appl. Mater. Interfaces, 2011, 3: 2358–2367 Energy Environ. Sci., 2011, 4: 3448-3455 CrystEngComm, 2012, 14: 4582–4588 Nature Communications, 2014, 5: 3813. DOI: 10.1038/ncomms4813 Scientific Reports, 2013, 3: 2017. DOI: 10.1038/srep02017 Figure 1. XRD of (top left) as-deposited, (bottom left) after annealing samples, and (right) the respective SEM pictures of the as-deposited samples. Figure 1

Design and optimization of a wideband impact mode piezoelectric power generator

This paper proposes a new design of an impact mode piezoelectric power generator that is able to operate in a wide frequency bandwidth by using a round piezoelectric ceramic as the energy converter. The evaluation results show that the output of the power generator can be optimized by implementing a so-called indirect impact configuration. To realize this type of configuration, a shim plate is placed between the piezoelectric ceramic and the hitting structure. At a certain base excitation frequency, the output efficiency of this configuration increases to about 4.3 times that of the direct impact configuration. Furthermore, it is demonstrated that the designated power generator is able to generate electric energy up to approximately 1.57mJ within 120s from the vibration of a moving vehicle.

Piezoelectric poly(vinylidene fluoride trifluoroethylene) thin film-based power generators using paper substrates for wearable device applications

Solution-derived poly(vinylidene fluoride trifluoroethylene) (P(VDF-TrFE)) piezoelectric thin films on cellulose paper substrates were prepared as flexible power generators for wearable device applications. Optimization of appropriate annealing and cooling sequences of the co-polymer films resulted in the formation of dense and uniform microstructures exhibiting a well-developed β-phase. A maximum open-circuit voltage of 1.5 V was generated from the periodic bending and releasing of the paper power generator at approximately 1 Hz. To demonstrate the wearable applications, P(VDF-TrFE) piezoelectric film-based paper power generators were directly attached on the back of a human hand, and they generated a maximum output open-circuit voltage of 0.4 V at low bending frequencies of 0.25 Hz. Good open-circuit voltage performance at low frequencies makes P(VDF-TrFE) piezoelectric thin films on paper substrates a strong candidate for future self-powered wearable devices.

Low‐frequency vibration‐based interdigital piezoelectric energy harvester and autonomous power regulating circuit

According to the difficult replacement and poor endurance of the battery for wireless sensor network nodes, a low-frequency vibration-based interdigital piezoelectric energy harvester and power regulating circuit (PRC) have been developed in this Letter. The proposed vibration pick-up structure consists of a rectangular flexible frame and series of cantilever beams interdigitally bonded to it. An efficient autonomous PRC with the function of energy storage, switch control, voltage regulation was also proposed. Experiment results show that a maximise output power of 18.8 μW could be produced by the proposed vibration energy harvesting system. The system's energy conversion efficiency could reach up to 72.3%, which made it the promising candidate of power supply for low power micro electron devices.

Enhanced Output Power of PZT Nanogenerator by Controlling Surface Morphology of Electrode.

Piezoelectric power generation using Pb(Zr,Ti)O3(PZT) nanowires grown on Nb-doped SrTiO3(nb:STO) substrate has been demonstrated. The epitaxial PZT nanowires prepared by a hydrothermal method, with a diameter and length of approximately 300 nm and 7 μm, respecively, were vertically aligned on the substrate. An embossed Au top electrode was applied to maximize the effective power generation area for non-uniform PZT nanowires. The PZT nanogenerator produced output power density of 0.56 μW/cm2 with a voltage of 0.9 V and current of 75 nA. This research suggests that the morphology control of top electrode can be useful to improve the efficiency of piezoelectric power generation.

Leveraging ZnO morphologies in piezoelectric composites for mechanical energy harvesting

In this work flexible composite nanogenerators were prepared aiming to identify and optimize the exploitation of the piezoelectric effect in mechanical energy harvesting. A novel shape-controlled synthesis of ZnO microstructures through hydrothermal route was achieved resulting in different morphologies and aspect-ratio particles, microwires, multipods, and desert-roses. The three different microparticles and round-shaped commercial nanoparticles were incorporated into a polydimethylsiloxane matrix and a comparative study on the piezoelectric output power dependence on the filler morphology was carried out. The highest performances, i.e. output voltage of 10V and a maximum power of 55µW, were obtained with the highest aspect-ratio ZnO filler, the microwires, dispersed in the PDMS matrix at a 40wt% concentration. Considering the generated voltage dependence on the size and aspect-ratio of the fillers, a working mechanism was formulated. The nanogenerators were then exploited to charge a homemade carbon-based supercapacitor. The voltage charging curves confirm the voltage generation trend based on the high aspect-ratio particles, showing that the best performances are obtained by the microwires-based composite nanogenerator. This work thus contributes to clarify the piezoelectric mechanism in composite nanogenerators and to maximize the output power generation in view of self-powered nanodevices able to recover and store waste environmental energy.

A mechatronic power boosting design for piezoelectric generators

It was shown that the piezoelectric power generation can be boosted by using the synchronized switch power conditioning circuits. This letter reports a self-powered and self-sensing mechatronic design in substitute of the auxiliary electronics towards a compact and universal synchronized switch solution. The design criteria are derived based on the conceptual waveforms and a two-degree-of-freedom analytical model. Experimental result shows that, compared to the standard bridge rectifier interface, the mechatronic design leads to an extra 111% increase of generated power from the prototyped piezoelectric generator under the same deflection magnitude excitation. The proposed design has introduced a valuable physical insight of electromechanical synergy towards the improvement of piezoelectric power generation.

Effect of shunted piezoelectric control for tuning piezoelectric power harvesting system responses—analytical techniques

This paper presents new analytical modelling of shunt circuit control responses for tuning electromechanical piezoelectric vibration power harvesting structures with proof mass offset. For this combination, the dynamic closed-form boundary value equations reduced from strong form variational principles were developed using the extended Hamiltonian principle to formulate the new coupled orthonormalized electromechanical power harvesting equations showing combinations of the mechanical system (dynamical behaviour of piezoelectric structure), electromechanical system (electrical piezoelectric response) and electrical system (tuning and harvesting circuits). The reduced equations can be further formulated to give the complete forms of new electromechanical multi-mode frequency response functions and the time waveform of the standard AC–DC circuit interface. The proposed technique can demonstrate self-adaptive harvesting response capabilities for tuning the frequency band and the power amplitude of the harvesting devices. The self-adaptive tuning strategies are demonstrated by modelling the shunt circuit behaviour of the piezoelectric control layer in order to optimize the harvesting piezoelectric layer during operation under input base excitation. In such situations, with proper tuning parameters the system performance can be substantially improved. Moreover, the validation of the closed-form technique is also provided by developing the Ritz method-based weak form analytical approach giving similar results. Finally, the parametric analytical studies have been explored to identify direct and relevant contributions for vibration power harvesting behaviours.

A New Method for Frequency Adjustment of Piezoelectric Energy Harvesters

A common piezoelectric power harvester consists of a piezoelectric patch on a cantilever beam with a tip mass at the end of the beam. The tip proof mass is essential to tune the harvester resonances towards an optimal operational frequency for energy harvesting. In this paper, a new experimental method is proposed; instead of using the tip mass, we use one or more jointed thin beams attached to the end of the cantilever beam. By adjusting the rotation angle of the joined beams, the resonance frequency of the energy harvester can be effectively tuned. This method allowed us to achieve more accurate and efficient frequency adjustments than the traditional tip mass method. The comparison between the two methods has been made. The effect of the one and two jointed beams is studied here by rotating angles of the joined beams.

Piezoelectric power extraction from bending waves: Electroelastic modeling, experimental validation, and performance enhancement

Existing research in vibration-based energy harvesting has focused mostly on the harvesting of deterministic or stochastic vibrational energy available at a fixed position in space. Such an approach is convenient for designing and employing linear and nonlinear vibration-based energy harvesters, such as base-excited cantilevers with piezoelectric laminates. This work presents a mathematical framework for the harvesting of one-dimensional bending waves propagating in infinite and semi-infinite beams as an alternative. For this purpose, the fully coupled electroelastic problem with piezoelectric patches bonded to a long slender beam is solved and conversion of incident wave energy into usable electricity while minimizing the traveling waves reflected and transmitted from the harvester domain is analyzed. The analysis shows that the efficiency of power transfer from elastic waves can be significantly improved beyond the typical wavelength matching in terms of both efficiency and bandwidth by resistive–inductive loading. It is also shown that enhancements to efficiency can be obtained by localized obstacles in mechanical domain, and fully anechoic boundary conditions can be obtained on finite beams by resistive–inductive impedance matching. These enhancement methods are most effective and practical when piezoelectric patch lengths and obstacle to patch distances are ∼>λ/4, where evanescent fields become insignificant, while the model can readily accommodate the presence of evanescent waves for arbitrary patch lengths. The validity and application of the proposed methods are demonstrated with experimental case studies using a long slender beam.

Vertically aligned epitaxial KNbO3 nanorod array for piezoelectric energy harvester and second harmonic generator

Vertical alignment of one-dimensional piezoelectric/ferroelectric materials is highly required to take full advantage of their unique electrical and optical properties for various applications. Here, we report the piezoelectric nanogenerator (NG) and second harmonic generator (SHG) applications of a vertically aligned single-crystalline KNbO3 (KNO) nanorod (NR) array on a conducting Nb:SrTiO3 substrate. A simple, cost-effective hydrothermal method at low temperature enables growth of ultra-long orthorhombic KNO NR array with a high piezoelectric coefficient. A corona-poled KNO NR array-based NG generates stable piezoelectric power under the compressive force. The open-circuit voltage and closed-circuit current almost linearly increase. In addition, the KNO NR array emits bright and sharp red, green, and blue visible light under the shining of infrared light. The SHG intensity is strongest along the KNO NR direction and weakest perpendicular to the NR direction. These results imply that the vertically aligned KNO NR array could be useful for an environment-friendly pressure sensor and a full-color display application.

Air Flow Conditions for Polymer Energy Harvesting

We present the results on the Karman vortex creations on the two circular cylinders. Changing the inlet velocity we examine static and dynamic pressure distributions. In such a configuration,a polymer piezoelectric foil, which could be placed inside turbulent boundary layers, can work as anenergy harvester. By matching the fluid flows predominant frequency with the natural frequency ofthe piezoelectric generator would maximize the piezoelectric power output.

Piezoelectric power harvesting from chirps and mating swiftlets attraction sound

The voltage measurement from piezoelectric disk (PZT) transducer is proposed in this paper. The attraction sound that has been used in the swiftlet farming industries was emitted at three different levels. The PZT was placed inside and outside the speaker to identify maximum power to produced high impulse voltage. The swiftlets sound was recorded using Avisoft software and analysed in Matlab. The sound was dividing into seven frames and it spectrum was plotted using Fast Fourier Transform (FFT) function to acquire the magnitude and frequency information. A Strip chart used to log and graph values acquired from PZT for 100 Hz sampling rate. The impulse response for each sample was saving in excel format and analysed in Matlab software. The finding showed, the voltage acquire from different type of swiftlets sound is significant different. In addition, the voltage generated from two PZT location also showed significant different. The reason can be highlight here is voltage generated by PZT is depending on the power of sound transmitted. The higher power sound transmitted the higher voltage generated from PZT.

Thermal fields of cylindrical piezoelectric electroacoustic transducers power constructions

Thermal fields of cylindrical piezoelectric electroacoustic transducers power constructions

Investigation on Resonant Vibration Performances of Fe‐Doped BiScO3–PbTiO3 Ceramics in High‐Temperature Environment

The high‐temperature performance of a series of Fe‐doped BiScO3‐PbTiO3 (BSPT) piezoelectric ceramics at the morphotropic phase boundary was investigated. The effects of different Fe contents on the piezoceramics were assessed with regard to variations in structure, morphology, dielectric properties, piezoelectric properties, and high‐temperature resonant vibration. X‐ray diffraction (XRD) results indicated that the Fe‐doped BSPT ceramics show a single perovskite structure and that the c/a ratio undergoes a slight increase with increasing Fe concentrations. It was also found that, as the proportion of Fe in the ceramics was increased, the grain size was enlarged somewhat, the dielectric loss (tan δ) decreased, the mechanical quality factor (Qm) was gradually improved, and the Curie temperature (TC) was increased from 426°C to approximately 460°C. Despite these complex effects, it was evident that Fe doping can improve the high‐temperature resonant vibration performance of BSPT ceramics, and that these materials exhibit stable resonant vibration velocities at temperatures as high as 225°C. Our results indicate that Fe‐doped BSPT ceramics have the potential to be used as piezoelectric power devices intended for high‐temperature environments.

Study of the effect of mechanical impact parameters on an impact-mode piezoelectric ceramic power generator

This paper presents an analytical and experimental study on the effect of mechanical impact parameters on impact-mode piezoelectric ceramic power generators. The parameters are the velocity and mass. The method of analysis is based on a weight drop experiment. The results show that the peak of the instantaneous output voltage is proportional to the impact velocity, and for the output power, it is in a straight line relationship with the same parameter. For the same velocity of impact, the advantage of using heavy objects is clear because its momentum and the impact force are higher. However, an adjustment in the velocity of impact is found to be more effective for higher instantaneous output power than the mass. This finding is supported by the output power that is generated by a 4-g steel ball with a momentum of 4.34g/s, which is almost 300% higher than that of an 8-g steel ball for the same momentum. The frequency responses of a vibration-based impact-mode piezoelectric ceramic power generator also support the same conclusion.

Power Generation from Airflow Induced Vibrations

This paper presents a coupled mechanical device that generates power by a direct conversion of the air flow into mechanical vibrations. The mechanism experiences a fluid force that changes with its orientation causing vibrations. The device consists of two tightly coupled parts: a mechanical resonator that produces high-frequency mechanical oscillations from quasi-steady airflow resulting in large amplitude vibrations and a piezoelectric power generator harvesting the energy from the resonator's motion. Assuming that the fluid-structure interactions solely depend on the instantaneous velocity, these interactions were studied using numerical modeling and wind-tunnel tests. The proposed energy harvester allows for locking up the device's lowest natural frequency to the vortex-shedding resonant frequency induced by the ambient energy source. The energy harvester demonstrated a peak-to-peak output voltage of 25V at 10Hz, from an input wind velocity of ∼7 m/s.

Lead-free ZnSnO3/MWCNTs-based self-poled flexible hybrid nanogenerator for piezoelectric power generation

A high-performance flexible piezoelectric hybrid nanogenerator (HNG) based on lead-free perovskite zinc stannate (ZnSnO3) nanocubes and polydimethylsiloxane (PDMS) composite with multiwall carbon nanotubes (MWCNTs) as supplement filling material is demonstrated. Even without any electrical poling treatment, the HNG possesses an open-circuit voltage of 40 V and a short-circuit current of 0.4 μA, respectively, under repeated human finger impact. It has been demonstrated that the output volume power density of 10.8 μW cm−3 from a HNG can drive several colour light emitting diodes (LEDs) and a charge capacitor that powers up a calculator, indicating an effective means of energy harvesting power source with high energy conversion efficiency (∼1.17%) for portable electronic devices.

Study of the Ambient Vibration Energy Harvesting Based on Piezoelectric Effect

The resonance between piezoelectric vibrator and the vibration source is the key to maximize the ambient vibration energy harvesting by using piezoelectric generator. In this paper, the factors that influence the output power of a single piezoelectric vibrator are analyzed. The effect of geometry size (length, thickness, width of piezoelectric chip and thickness of metal shim) of a single cantilever piezoelectric vibrator to the output power is analyzed and simulated with the help of MATLAB (matrix laboratory). The curves that output power varies with geometry size are obtained when the displacement and load at the free end are constant. Then the paper points out multi-resonant frequency piezoelectric power generation, including cantilever multi-resonant frequency piezoelectric power generation and disc type multi-resonant frequency piezoelectric generation. Multi-resonant frequency of cantilever piezoelectric power generation can be realized by placing different quality mass at the free end, while disc type multi-resonant frequency piezoelectric generation can be realized through series and parallel connection of piezoelectric vibrator.

Analysis and Optimization of a Piezoelectric Harvester on a Car Damper

Low power levels obtained from piezoelectric conversion of ambient vibrations appear to be a promising solution to supply wireless sensors embedded inside automotive suspension. However such a solution requires overall an optimum power extraction from the piezoelectric power harvester. This leads to the use of a sufficiently accurate and flexible modelling method to find the optimal characterics and configuration of the harvester. To this end, an innovative bond graph model of the piezoelectric harvester embedded in the quarter vehicle system is proposed for providing the harvested power when a car travels a road with a speed bump at 30km/h. Results show that around of 0.5 milliwatt electrical power is harvested when varying key parameters like the location and characteristics of the piezoelectric device.