Piezoelectric Structures Research Articles

Piezoelectric Structure With a 3-D Printed Mesh Layer

Dielectric structures containing ferroelectret layers are commonly investigated because of their high piezoelectric activity. The mechanical properties of electret–gas-only ferroelectrets are limited; therefore, new layered structures containing nonelectret materials are explored. Separation of requirements related to the mechanical and electrical properties of particular layers is the latest concept to achieve structures with a higher piezoelectric response. This article presents an exemplary dielectric-layered structure exhibiting piezoelectric activity, where 3-D printed polylactic acid (PLA) mesh layer, polypropylene (PP) electret foil, and elastomer top layer are applied. The piezoelectric coefficient <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${d}_{33}$ </tex-math></inline-formula> , measured under static conditions, is found to be at the level of 300 pC <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\cdot \text{N}$ </tex-math></inline-formula> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> . The simplified model of the structure is proposed to allow for the determination of the piezoelectric coefficient <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${d}_{33}$ </tex-math></inline-formula> . Due to the presented model, an improvement of the piezoelectric response is possible by optimizing the electrical properties and geometry of the particular layers. A comparison of calculated and measured values of the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${d}_{33}$ </tex-math></inline-formula> coefficient confirms the validity of the proposed model. The influence of the poling voltage and the static pressure on the structure piezoelectric properties is experimentally examined.

Controllable electromechanical stability of a torsional micromirror actuator with piezoelectric composite structure under capillary force

Various types of micro/nano functional devices are being widely designed as optical switches, micro scanners, micromirrors and other core optical devices. The continuing miniaturization of the functional devices makes the size dependence of electromechanical property significant in micro/nano scale due to the sharp increase of surface interactions such as capillary force from liquid bridge, van der Waals and Casimir forces from quantum fluctuations. The surface interactions can cause the pull-in instability, adhesion between parts, and even failure of device. This work provides an active control method to avoid the pull-in instability of an electrostatically driven circular micromirror by applying voltage on a torsional piezoelectric composite structure. The influences of the three types are compared of dispersion forces on the electromechanical stability of the micromirror actuator. A comprehensive electromechanical model of a torsional piezoelectric beam was established to numerically investigate the electromechanical coupling of the micromirror. The results show that the influence of capillary force on the stability of the micromirror is as significant as van der Waals force and Casimir force. By introducing piezoelectric nanoplates into the laminated torsional structure, the micromirror stability can be controlled based on the piezoelectric effect of the torsional piezoelectric composite structure. This work can contribute to the structural optimization design and manufacture of micromirror systems. Cited as: Liu, M., Chen, Y., Cheng, W., Chen, S., Yu, T., Yang, W. Controllable electromechanical stability of a torsional micromirror actuator with piezoelectric composite structure under capillary force. Capillarity, 2022, 5(3): 51-64. https://doi.org/10.46690/capi.2022.03.02

Design and simulation of cavity and piezoelectric material structure in segmented doubly clamped piezoelectric energy harvester

AbstractIn view of providing consistent power to remotely situated microelectronic devices, this paper proposes a full‐length cavity‐based novel segmented doubly clamped piezoelectric energy harvester (DCPEH). The paper starts with the analysis of different possible configurations of segmented DCPEH beam corresponding to single, double, and triple cavity systems involvement. It has been observed that for full‐length single cavity involvement, the segmented DCPEH beam is resonate at minimum value (70 Hz) of resonance frequency. However, the observed value of output power response (76 mW) at such low resonant frequency is not so appropriate. Therefore, the performance of full‐length cavity‐based segmented DCPEH beam has been further investigated for series and parallel composite structural design of PMN‐35%PT (M1) and PZT‐5H (M2) piezoelectric materials. The improved value of output power (313 mW) response at low (68.8 Hz) resonant frequency has been achieved with M2‐M1 series composite form of piezoelectric materials.

Asymmetric non-slipping adhesion behavior of layered piezoelectric structures

Layered piezoelectric structures have found wide applications in micro-electro-mechanical systems (MEMS) due to their intrinsic electro-mechanical coupling effect. The adhesion effect resulting from various surface forces (e.g., the electrostatic force, capillary force, and Van der Waals force) has become one dominant factor in determining the reliability and service life of the MEMS devices. In this study, the asymmetric non-slipping adhesion behavior of layered piezoelectric structures under the action of different external loadings is investigated. A system of coupled singular integral equations are obtained for the stated problem in the framework of the generalized JKR theory, where the coupling effect between the normal and tangential contact stresses is taken into consideration. The closed-form analytical solutions of the electric displacement and stress fields within the contact zone are derived. The relations between the contact size and applied loadings are set up with the Griffith energy balance criterion. The effect of the mechanical and electric loads and the mismatch strain on the adhesion behavior of layered piezoelectric structures is discussed in detail. It is found that applying the electric load can only strengthen the adhesion effect for different types of layered piezoelectric structures. Both the inclined angle of the mechanical force and the geometric parameter of the contacting objects have significant effects on the adhesion behavior. The results obtained from present paper should be very useful for understanding the adhesion failure mechanism of the MEMS devices composed of layered piezoelectric structures.

A Magnetically Coupled Piezoelectric-Electromagnetic Low-Frequency Multidirection Hybrid Energy Harvester.

The traditional single electromechanical conversion energy harvester can collect energy only in a single vibration direction. Moreover, it requires high environmental vibration frequency, and its output power is low. To solve these problems, a cross-shaped magnetically coupled piezoelectric–electromagnetic hybrid harvester is proposed. The harvester comprised a ring-shaped support frame, a piezoelectric generation structure, and an electromagnetic generation structure. The harvester could simultaneously generate energy piezoelectrically and electrically, in addition, it could generate electricity efficiently at a lower environmental vibration, and it can collect the energy in two vibration directions simultaneously. To verify the effectiveness of the device, we set up a vibration experiment system and conducted comparative experiments about non-magnetically coupled piezoelectric, magnetically coupled piezoelectric, and magnetically coupled piezoelectric–electromagnetic hybrid energy harvesters. The experimental results showed that the output power of the magnetically coupled piezoelectric–electromagnetic hybrid energy harvester was 2.13 mW for the piezoelectric structure and 1.76 mW for the electromagnetic structure under the vibration of single-direction resonant frequency. The total hybrid output power was 3.89 mW. The hybrid harvester could collect vibration energy parallel to the ring in any direction. Furthermore, compared with the non-magnetically coupled piezoelectric energy harvester and the magnetically coupled piezoelectric energy harvester, the output power was increased by 141.6% and 55.6%, respectively.

Vibration detection technology research based on piezoelectric cantilever

This paper studies the vibration detection technique based on the piezoelectric cantilever structure, and analyzes the relationship between the resonance frequency and the structure parameters. Although the output of the electrical signal is too small, it can be used to detect vibration during resonance with the maximum output voltage. A vibration testing device is designed based on piezoelectric cantilever structure, because in the vibration environment of the same frequency the vibration detection technology can obtain larger electrical signals. It can realize the automatic detection of real-time vibration state, and the vibration energy can charge the power supply through the energy storage circuit. Through the experimental method to verify relationship between the output voltage of piezoelectric cantilever beam, mass block, piezoelectric cantilever structure parameters and frequency, the experimental value of resonance frequency is very close with theoretical calculation value. The experimental resonant frequency of the designed piezoelectric cantilever beam is 16.5 Hz, which is slightly lower than the theoretical value of resonant frequency of 17.6 Hz, and the peak value of the piezoelectric output open-circuit voltage is 7.1 V.

Preparation and Performance of a Box-Type Bending Piezoelectric Transducer

Pavement-based piezoelectric power-generation technology converts mechanical energy generated by traffic loads into electricity by embedding piezoelectric transducers in the pavement. However, existing piezoelectric transducer structures are mostly the direct-impact type and the piezoelectric ceramic materials can be easily damaged. To reduce the risk of damage, a box-type bending piezoelectric energy transducer was designed and prepared in this study. The transducer is composed of 27 fixed piezoelectric sheets connected at both ends in parallel. The external casing uses a box-type structure with upper, middle and lower components. Under typical traffic load conditions, an excitation frequency of 10 Hz and displacement of 2 mm, the maximum output voltage was 30.17 V, the maximum output current was 10.01 mA and the maximum output power was 303.4 mW under load resistance of 3 kΩ. The output power of the transducer increases with loading frequency and displacement. Finally, the output power of the proposed transducer is much higher than that of existing transducers. This new piezoelectric transducer has good prospects for use in energy-generating pavement engineering applications.

Design and Comparative Study of a Small-Stroke Energy Harvesting Floor Based on a Multi-Layer Piezoelectric Beam Structure.

Recently, research on the energy harvesting floor is attracting more and more attention due to its possible application in the smart house, invasion monitoring, internet of things, etc. This paper introduced a design and comparative study of a small-stroke piezoelectric energy harvesting floor based on a multi-layer piezoelectric beam structure. The multi-layer piezoelectric beams are designed based on simply supported beams in an interdigitated manner. Theoretical analysis is explored to find out the beam number and layer number of the structure. Through this design, the input power from the human footsteps was effectively utilized and transformed into electrical power. The designed piezoelectric energy harvesting floor structure was tested by our designed stepping machine, which can simulate the stepping effect of a walking human on the floor with different parameters such as stepping frequency. Comparative studies of the energy harvester are carried out regarding different stepping frequencies, external circuits, and initial beam shapes. The experimental results showed that the maximum output power of a group of four-layer prototypes was 960.9 µW at a stroke of 4 mm and a step frequency of 0.83 Hz, with the beams connected in parallel.

Single-sensor pressure-gradient piezoelectric cylindrical tube vector hydrophone

A single-sensor differential pressure vector hydrophone based on a radially polarized piezoelectric circular tube structure is proposed, which can realize the azimuth angle of the incident acoustic wave by using the scalar information of the underwater sound field through a single sensor without any priori conditions. It has the characteristics of simple structure and low cost. The proposed hydrophone is improved based on the piezoelectric circular tube structure. And its piezoelectric ceramics are divided into eight parts. Through the different response voltages of each part, the underwater sound field scalar information received by a single sensor is used, combined with signal processing algorithms, the azimuth angle of the incident sound wave is estimated. The finite element method is used to complete the simulation of the hydrophone, and the simulation results are analyzed and fitted. Through the mockup test, comparing the results, and combining with the fitting formula, it is verified that the hydrophone can estimate the azimuth angle of the incident sound wave without any priori conditions.

Phase field fracture modeling of transversely isotropic piezoelectric material with anisotropic fracture toughness

Fracture analysis of piezoelectric devices and structures is of great importance in science and engineering. In the present work, a new phase field fracture model in the context of transversely isotropic electro-elasticity is developed by means of the variational method. A structural tensor is introduced in the crack surface density function to quantify the anisotropy in fracture toughness. To characterize the asymmetric fracture behavior of piezoelectric solid, the contribution of the mechanical energy is employed to drive the crack propagation. An efficient and robust staggered scheme is adopted to deal with the corresponding fracture problems, which is implemented in the commercial finite element software Abaqus. Numerical simulations are carried out to investigate the effect of the anisotropic fracture toughness, poling direction and external electrical field on the fracture behavior of the piezoelectric materials. The anisotropic fracture toughness would significantly affect the crack path and fracture load. With the help of the nonlinear regression method, a phenomenological model is proposed to predict the fracture load. The present researches may benefit the safety assessment of piezoelectric materials in practical applications.

Sponge-like piezoelectric micro- and nanofiber structures for mechanical energy harvesting

Herein, the one-step fabrication of novel three-dimensional sponge-like piezoelectric electrospun nanofiber structures is reported. Ferroelectric polymers are biocompatible and flexible materials that present attractive opportunities for the fabrication of portable energy harvesters for energy efficient wearable electronic devices. While being compatible with diverse fabrication methods, thicker and denser 3D forms have only been obtained from extruder-based, low-yield approaches. Electrospinning polyvinylidene fluoride (PVDF) and polyvinylidene fluoride-co-trifluoroethylene (PVDF-TrFE) solutions with added polyethylene oxide (PEO) and lithium chloride was explored as an alternative approach for the scaled-up fabrication of 3D structures. The resulting PVDF/PEO and PVDF-TrFE/PEO 700 µm thick sponge-like fiber mats were used as active cores for piezoelectric generators. The produced sponge-like core generators achieved an average peak-to-peak voltage of 69.4 V when subjected to a 1.58 N impact force applied at a frequency of 4 Hz and connected to a 15.1 M Ω resistive load. Their measured instantaneous output power of 40.7 µW cm–2 exceeds that of similar state-of-the-art generators by a factor of 2. Our fabrication method provides a low-cost, one-step, and scalable alternative for creating micro- and nanofibrous three-dimensional structures.

The static and dynamic analysis for the coupling hygro-electro-mechanical multifield problems via stabilized node-based smoothed radial point interpolation method

In this article, the static and dynamic coupling hygro-electro-mechanical (CHEM) multifield problems of piezoelectric structures are investigated via stabilized node-based smoothed radial point interpolation method (SNS-RPIM). The basic equations for the CHEM problems are derived. And the static and dynamic responses are calculated by SNS-RPIM and finite element method. Through the numerical examples, the superiority of proposed method is also validated. These solutions also indicate that the increase of moisture concentration makes the model softer and decreases the structural stiffness when considering moisture dependence of the elastic coefficients, which also leads to the decrease of frequency and variation of displacement.

Angular poling effect on cymbal piezoelectric structure using rhombohedral and tetragonal PMN-0.33PT for energy harvesting applications

Angular poling effect on cymbal piezoelectric structure using rhombohedral and tetragonal PMN-0.33PT for energy harvesting applications

Characterization of Piezoelectric Properties of Ag-NPs Doped PVDF Nanocomposite Fibres Membrane Prepared by Near Field Electrospinning.

In this study, Near-field electrospinning (NFES) technique is used with a cylindrical collector to fabricate a large area permanent piezoelectric micro and nanofibers by a prepared solution. NFES requires a small electric field to fabricate fibers Objective: The objective of this paper to investigate silver nanoparticle (Ag-NP)/ Polyvinylidene fluoride (PVDF) composite as the best piezoelectric material with improved properties to produced tremendously flexible and sensitive piezoelectric material with pertinent conductance Methods: In this paper, we used controllable electrospinning technique based on Near-field electrospinning (NFES). The process parameter for Ag-NP/PVDF composite electrospun fiber based on pure PVDF fiber. A PVDF solution concentration of 18 wt.% and 6 wt.% silver nitrate, which is relative to the weight of PVDF wt.% with 1058 μS conductivity fibers, have been directly written on a rotating cylindrical collector for aligned fiber PVDF/Ag-NP fibers are patterned on fabricated copper (Cu) interdigitated electrodes were implemented on a thin flexible polyethylene terephthalate (PET) substrate and Polydimethylsiloxane (PDMS) used as a package to enhance the durability of the PVDF/ Ag-NP device. A notable effect on the piezoelectric response has been observed after Ag-NP addition, confirmed by XRD characterization and tapping test of Ag-NP/PVDF composite fiber. The morphology of the PVDF/Ag-NP fibers and measure diameter by scanning electron microscopy (SEM) and Optical micrograph (OM), of fiber. Finally, a diameter of PVDF/Ag-NP fibers up to ~7 μm. The high diffraction peak at 2θ = 20.5˚ was investigated by X-ray diffraction (XRD) in the piezoelectric crystal β-phase structure. Further addition of silver nanoparticles (Ag- NPs) in the PVDF solution resulted in enhancing the electromechanical conversion of the fibers from ~0.1 V to ~1 V. In conclusion, we can say that confirmed and validated the addition of Ag-NP in PVDF could enhance the piezoelectric property by using NFES technique with improved crystalline phase content can be useful for a wide range of power and sensing applications like biomedical devices and energy harvesting, among others.

Remarks on the scattering phenomena of love-type wave propagation in a layered porous piezoelectric structure containing surface irregularity

The present analysis adduces the scattering of Love-type wave in a composite structure comprised of an irregular porous piezoelectric layer nested on a porous piezoelectric substrate. The dispersion equation for the scattering of Love-type waves in the aforesaid composite structure have been derived. The impacts of the parameters associated with the piezoelectricity of the upper layer on the phase and group velocities are also observed. The effect of vertical irregularity parameter, piezoelectricity of upper layer, and porosity of the upper layer on the reflected mechanical displacement and electrical potential functions (for both solid and fluid phases) have also been examined.

Complete guided wave in piezoelectric nanoplates: A nonlocal stress expansion polynomial method

Taking the size-dependent and piezoelectric effect into account, the complete guided waves in nonlocal piezoelectric nanoplates are investigated. The Legendre polynomial method based on stress and electric displacement expansion is proposed to obtain the complete dispersion curves in the complex domain. The nonlocal and piezoelectric effects on propagative and evanescent waves are discussed. It is found that the nonlocal effect improves the phase velocity of complex Lamb wave, while reduces the attenuation and frequency bandwidth of complex Lamb wave. The stiffness-softening effect of the nonlocal structure reduces the phase velocity, cut-off frequency and escape frequency of propagative waves, while the stiffness-hardening effect of the piezoelectric structure increases the phase velocity, cut-off frequency and escape frequency of propagative waves. In addition, the nonlocal effect increases the piezoelectric effect, while the piezoelectric effect weakens the nonlocal effect on phase velocity.

Highly (00l)-textured BiFeO3 thick films integrated on stainless steel foils with an optimized piezoelectric performance

Piezoelectric BiFeO3 films were successfully prepared on 304 stainless steel (SS) foils via RF-magnetron sputtering at 450 °C. By adopting a LaNiO3/Pt/Ti tri-layer bottom electrode, a predominant (100)-orientation and a better crystalline morphology were achieved in the BiFeO3 film, resulting in better ferroelectric and dielectric properties targeted for piezoelectric applications than those directly grown on SS or LaNiO3/SS. These properties include a large remnant polarization (Pr~68 μC/cm2), a large coercive field (Ec~241 kV/cm) and a sizable self-bias (Ebi~ 158 kV/cm), as well as a low dielectric constant and a reduced dielectric loss (εr≤200 and tan δ ≤ 0.026 in 1 kHz-1 MHz). Based on this optimal BiFeO3-SS heterostructure, large converse and direct transverse piezoelectric coefficients |e31,f| ~ 1.7 C/m2 and 1.07 C/m2 were achieved in prototype piezoelectric actuator and energy harvester structures, respectively. These results suggest that BiFeO3-SS heterostructures have a great potential for applications in lead-free, metal-based piezoelectric micro-electro- mechanical systems (piezo-MEMS).

An energy harvester with nanoporous piezoelectric double-beam structure

An energy harvester with nanoporous piezoelectric double-beam structure

FEM implementation of the nonlinear damage evolution model for piezoelectric material under bipolar electrical fatigue load

The service life of piezoelectric actuator is significantly affected by the high electric fatigue load. Predicting damage evolution in piezoelectric materials under high electric load is essential for the reliability and life prediction of piezoelectric structures and devices. In this paper, a nonlinear damage evolution FE model and its acceleration program are proposed which are capable of modeling nonlinear damage evolution of piezoelectric material and structure under high electric fatigue load. The simulation results of degraded piezoelectric constant varying with the number of cycles are compared with the experimental results, and a well agreement verifies the validity of the nonlinear damage evolution FE model. Moreover, the damage distribution evolution of piezoelectric multi-layer actuator with standard double comb electrode is studied by the proposed nonlinear damage evolution model. The driving performance of piezoelectric multi-layer actuator decreases rapidly under the high electric fatigue load, where the damage area starts from the tip of the electrode and gradually spreads to the area between the electrodes. Based on the nonlinear damage evolution and its FEM implementation, the damage distribution and evolution for piezoelectric structures with variable amplitude bipolar electrical fatigue load can be obtained. This provides a reliable reference for the life prediction and application of the piezoelectric actuator.

Indentation of piezoelectric micro- and nanostructures

This study is focused on obtaining a comprehensive understanding of the influence of geometry — size and shape — on the indentation response of a large set of piezoelectric small-volume structures such as nanoislands, nanowires and thin films. Using three-dimensional finite element modeling, the complex interplay between the properties of the indented materials and the indentation response of piezoelectric micro- and nanostructures is analyzed. It is demonstrated that: (i) In general, the indentation response of thin film structures tends to be much stiffer than that of the piezoelectric nanoisland and nanowires, resulting in more charges being generated during the indentation of the thin-film structures. (ii) The indentation of the piezoelectric nanowire structures with a spherical indenter whose radius is substantially larger than the width of the nanowires, introduces a combination of deformation modes — structural bulging and indentation-induced compression. The combined effect of two deformation modes produces a maximum in the charges generated during the indentation process on a nanowire structure with a particular aspect ratio (i.e., wire width/wire height), which is greater than that produced in nanoisland and thin films structures with the same characteristic size.