Electromechanical Coupling Properties Research Articles

Multiple electromechanical coupling in wrinkled monolayer MoS2

Abstract The electromechanical coupling of two-dimensional (2D) transition metal dichalcogenides (TMDs) is crucial for the design of highly efficient optoelectronic devices. However, achieving multiple electromechanical coupling effects in one 2D material remain a major challenge. Here, we investigate the coexistence of energy funneling, piezoelectricity, and flexoelectricity in wrinkled monolayer TMDs through the atomic-bond-relaxation approach. We find that the periodic undulation strain induced by wrinkles can lead to multiple electromechanical coupling properties. The synergistic interaction of energy funneling, piezoelectric, and flexoelectric effects can result in spatially orthogonal charge separation and transport, as well as the suppression of recombination during charge separation and transport processes. Our study provides a new route for the design of 2D material based optoelectronic devices.

Full field crack solutions in anti-plane flexoelectricity

In flexoelectric materials, strain gradients can induce electrical polarization. However, internal defects such as cracks profoundly affect the electromechanical coupling properties of flexoelectric solids. In particular, anti-plane cracks involve less physical fields, which are easier to study. In this study, we present a comprehensive and innovative investigation of the anti-plane crack problems in flexoelectric materials, including semi-infinite and finite-length anti-plane cracks. For the first time, we formulate a full-field solution for semi-infinite anti-plane cracks in flexoelectric media by applying the Wiener–Hopf technique. Furthermore, the collocation method and the Chebyshev polynomial expansion are used for the first time to derive the full-field hypersingular integral equation solution for finite-length anti-plane cracks in flexoelectric solids. In addition, a comparative analysis between the full-field and asymptotic solutions for semi-infinite cracks is performed, shedding light on the discrepancies in the representation of the electromechanical coupling behavior near the crack tip. The mixed finite element method is used to compare with the full-field solutions of finite-length cracks. The agreement between the numerical results and the full-field solutions demonstrates the rigor of our study. This research advances the knowledge of defects in flexoelectricity and provides significant insight into relevant failure mechanisms.

A purely centered and non-redundant piezoelectric stick-slip rotary stage with force amplification

This paper proposes a purely center-rotation and non-redundant piezoelectric stick–slip rotary stage with force magnification. A bridge driving mechanism with centrosymmetric actuation feet is proposed, and its tilt angle can be adjusted to regulate the clamping force amplification characteristics, thus improving load capacities. Meanwhile, only a single piezoelectric actuator is used, and the driving mechanism is built in the circular slider, hence achieving non-redundant, purely centered rotation and improving the structural compactness. Theoretical calculations and simulation analyses of single-step rotation angles and force amplification of the rotary stage are carried out. In addition, a system dynamics model with electromechanical, rigid-flexible, and friction coupling properties is established. Finally, a prototype is fabricated, and various experiments are conducted. The designed bridge driving mechanism amplifies the piezoelectric actuation force by 2.8 times, and the stick–slip rotary stage has a maximum load of up to 9 kg. Also, the stage can rotate more than 360°, and the angular resolution is 0.1265 μrad, demonstrating superior performances of the non-redundant center-rotation stage.

Chromium‐substituted bismuth titanate–niobate exhibiting superior piezoelectric performance for high‐temperature applications

AbstractHigh‐temperature piezoelectric ceramics with excellent piezoelectric properties are key materials for high‐temperature piezoelectric devices. In this context, bismuth titanate–niobate (Bi3TiNbO9) is one of the most promising candidates, owing to its high Curie temperature (TC) > 900°C. However, the relatively low piezoelectric response of prototype Bi3TiNbO9 does not satisfy the requirements of high‐precision and high‐sensitivity applications. Herein, chromium‐substituted Bi3TiNbO9 with a nominal composition, Bi3Ti1−xCrxNbO9 (BTN‐100xCr), was prepared using the solid‐state reaction method. Raman spectroscopy and X‐ray diffraction refinements revealed structural distortions induced by the substitution of chromium. Piezo‐response force microscopy and ferroelectric hysteresis loops showed facile polarization reversal and domain wall movement in chromium‐substituted Bi3TiNbO9. The resultant structural distortion and domain wall movement served as intrinsic and extrinsic contributions to the enhancement of the piezoelectric properties, respectively. Consequently, BTN‐1.5Cr exhibits a high piezoelectric constant (d33) of 17.7 pC/N, which is four times that of Bi3TiNbO9 (4.2 pC/N), a high TC of 908°C, and an excellent thermal stability of piezoelectric and electromechanical coupling properties up to 500°C. These results indicate that chromium substitution enhances the high‐temperature piezoelectric properties of Bi3TiNbO9, and chromium‐substituted Bi3TiNbO9 is a promising candidate for high‐temperature piezoelectric applications.

Thickness and temperature dependence performances for single crystal composites by different polarization conditions

Alternating current polarization (ACP) has been demonstrated to enhance the performance of 1-3 piezoelectric single crystal composites (PSCCs), compared to direct current polarization (DCP). However, the scaling effect and temperature stability of PSCCs under different polarization modes, which are of significance to practical applications, have rarely been studied. Here, we compared and analyzed the thickness and temperature-dependent properties of PSCCs under ACP and DCP. The results indicated that ACP PSCCs have improved piezoelectric, electromechanical coupling, and dielectric properties. There were scaling effects for PSCCs with thickness below 400 μm. Compared to high-thickness PSCCs, the piezoelectric coefficient (d33), free dielectric constant (ε33Tε0) as well as thickness electromechanical coupling factor (kt) of low-thickness samples were inferior and the corresponding performance enhancements under ACP were also relatively low. In contrast, the clamped dielectric constant (ε33Sε0) did not show significant thickness correlation. As for temperature stability, all performances of PSCCs improved with increase in temperature and the performance enhancement with temperature change was not dependent on the polarization conditions. This work provides reference significance of selecting appropriate polarization for PSCCs, thus benefiting the design and preparation for transducers.

Origin of strong piezoelectric enhancement in bismuth titanate‐ferrite for high‐temperature applications

AbstractAdvancing the development of high‐temperature piezoelectric devices requires high‐performance piezoelectric materials with high Curie temperature, where charge signals can be efficiently collected at elevated temperatures. Recent investigations indicate that bismuth titanate‐ferrite (Bi5Ti3FeO15) is a good high‐temperature piezoelectric material because of its high Curie temperature (TC > 760°C). However, the piezoelectric performance of Bi5Ti3FeO15‐based compounds has not been extensively studied because of their extremely poor piezoelectric performance and low direct current electrical resistivity at elevated temperatures. Herein, we reported the strong piezoelectric performance enhancement in Bi5Ti3FeO15, with the nominal compositions of Bi5‐xEuxTi3FeO15 (BTF‐100xEu). X‐ray diffraction Rietveld refinements and Raman spectra reveal an enhanced lattice distortion in europium‐substituted Bi5Ti3FeO15, which is mainly dominated by rotation distortion. The increased domain wall density that detected by out‐of‐plane piezoelectric force microscopy is in favor of domain wall movement and polarization reversal. Both of the enhanced lattice distortion and the increased domain wall density contribute to the piezoelectric enhancement in Bi5Ti3FeO15, as a result, the optimal composition of BTF‐8Eu exhibits a large piezoelectric constant d33 of 24 pC/N, three times higher than that of Bi5Ti3FeO15. Importantly, BTF‐8Eu exhibits high TC of 782°C, excellent in‐situ piezoelectric response (>94% that of the initial value at room temperature), and stable electromechanical coupling properties up to 400°C. This work reveals the origin of strong piezoelectric enhancement in europium‐substituted Bi5Ti3FeO15 results from the intrinsic contribution of structure distortion and the extrinsic contribution of ferroelectric domain.

Piezoelectric dual network dressing with adaptive electrical stimulation for diabetic infected wound repair via antibacterial, antioxidant, anti-inflammation, and angiogenesis

Electrical stimulation therapy plays a crucial role in the healing of wounds. However, electrical stimulation based on piezoelectric materials faces limitations in dynamically matching cell activity and lacks anti-infection properties, thereby restricting its broader clinical application. Herein, a piezoelectric dual network nanofiber dressing (CuEG/PVDF) was prepared using copper/ epigallocatechin 3-gallate (Cu2+/EGCG) and polyvinylidene fluoride (PVDF). This dressing constructs dynamic force-electrical closed-loop feedback signals through cell adhesion and adaptive electrical stimulation to accelerate the healing of infectious diabetic wounds. Benefiting for the Cu2+-EGCG metal-polyphenol network, it enhances the electromechanical coupling properties, hydrophilicity, and cell adhesion of the piezoelectric double network dressing. Cell proliferation and migration were promoted by increased adhesion area, enhanced adaptive electrical stimulation, and active calcium influx. Moreover, CuEG/PVDF demonstrate significant antibacterial, antioxidant, anti-inflammatory, and angiogenic activities. In vivo experiments demonstrate that this dual-network piezoelectric dressing reduces the inflammatory response in rats, eliminates Methicillin-resistant Staphylococcus aureus (MRSA), and accelerates wound repair. Overall, this study presents a promising strategy for implementing electrical stimulation in the treatment of infected wounds.

Electromechanical Deformations and Bifurcations in Soft Dielectrics: A Review.

Dielectric elastomers have attracted considerable attention both from academia and industry alike over the last two decades due to their superior mechanical properties. In parallel, research on the mechanical properties of dielectrics has been steadily advancing, including the theoretical, experimental, and numerical aspects. It has been recognized that the electromechanical coupling property of dielectric materials can be utilized to drive deformations in functional devices in a more controllable and intelligent manner. This paper reviews recent advances in the theory of dielectrics, with specific attention focused on the theory proposed by Dorfmann and Ogden. Additionally, we provide examples illustrating the application of this theory to analyze the electromechanical deformations and the associated bifurcations in soft dielectrics. We compared the bifurcations in elastic and dielectric materials and found that only compressive bifurcation modes exist in elastic structures, whereas both compressive and tensile modes coexist in dielectric structures. We summarize two proposed ways to suppress and prevent the tensile bifurcations in dielectric materials. We hope that this literature survey will foster further advancements in the field of the electroelastic theory of soft dielectrics.

Simulation and structural design of 2–2 PIMNT/epoxy piezoelectric composites

Piezoelectric materials are commonly used in transducers to convert electromechanical signals due to their energy conversion characteristics. We designed a PIMNT/epoxy 2–2 composite to take full advantage of the excellent beam-mode piezoelectric and acoustic features of PIMNT single crystals. Following the approach used for piezoelectric ceramic composites, we selected PIMNT piezoelectric single crystal and EPO-TEK301-2 epoxy resin for the composite, and combined finite element analysis with experimental preparation. We prepared, tested and analyzed 2–2 piezoelectric single crystal composites with varying volume fractions, which showed high electromechanical coupling properties ([Formula: see text]%) and low acoustic impedance ([Formula: see text][Formula: see text]MRayl). These encouraging findings suggest the possibility of devising high-performance ultrasonic transducers utilizing the PIMNT/epoxy 2–2 composite.

Concurrent topology optimization of multiscale piezoelectric actuators

As an important component of smart structural devices, piezoelectric composites have strong macroscopic electromechanical coupling properties which often depend on their microstructural geometries and material parameters. Therefore, optimizing the microstructural design is crucial for achieving the desired macroscale effective properties. To this end, this paper conducts a concurrent multiscale topology optimization (TO) to optimize the material distribution of piezoelectric actuators, aiming to maximize the electrical and mechanical energy transmission to meet specific engineering requirements. Firstly, an energy method is used to homogenize the microstructures and obtain the effective parameters of the piezoelectric material. Then, the piezoelectric material with penalization and polarization (PEMAP-P) approach in conjunction with the adjoint method is employed to calculate the sensitivity of objective and constraint functions. The sensitivities at both the macroscale and microscale are obtained by considering the interscale coupling effects. Finally, the concurrent bi-level iteration based on the optimality criteria (OC) or the method of moving asymptotes (MMA) is conducted. Through this research, we have illuminated the relations between the optimized performance of the actuator and the material volume fractions at each scale. We have also compared in detail the differences between two-scale and single-scale designs, as well as the differences between the simplified half-symmetric geometric model and the full geometric model. We find that a larger volume fraction of material either at the macroscale or microscale generates a larger transmitted displacement magnitude under the same applied electric field, and for a given total material, the transmitted maximum increases with increasing microstructural volume fraction.

A NURBS-based IGA using zig-zag plate theory for nonlinear passive/semi-active damping analysis of laminated FG-CNTRC plates

This study introduces an efficient and versatile numerical approach for simulating passive/semi-active damping treatments on laminated structures composed of functionally graded carbon nanotube-reinforced composites (FG-CNTRC) plates. This novel approach integrates an isogeometric finite element formulation that leverages basic functions generated from Non-Uniform Rational Basis Spline (NURBS) with the Murakami zig-zag theory, Von Kármán’s nonlinear strain–displacement model, and the electro-mechanical coupling properties of the constraining layers. The proposed isogeometric formulation can be transformed into the Laplace domain using the Golla–Hughes–McTavish model to successfully simulate the time-dependent passive/semi-active damping mechanism of viscoelastic materials. Subsequently, results obtained in the Laplace domain are reconverted into the time domain using inverse techniques. The validation of the proposed model through two numerical examples showcases its high reliability and demonstrates the feasibility of simulating and controlling FG-CNTRC plates with various geometries within a Computer-Aided Design-Computer-Aided Engineering (CAD-CAE) analysis framework.

Quantitative domain evaluation in rhombohedral BS-PT piezoelectric ceramics via diffraction-plane-transformation model

The domain structure fundamentally determines the piezoelectric/ferroelectric performance of ferroelectric materials. To understand the correlation between macro-properties and microstructure, the evolution of domain structure should be clearly figured out. Here, the diffraction-plane-transformation (DPT) model is proposed for the domain evaluation in BS-PT piezoelectric ceramics of rhombohedral crystalline structure. The transformation between different crystal planes is accurately revealed by the DPT model. Then, non-180° domain reversal in rhombohedral 0.4BiScO3–0.6PbTiO3 piezoelectric ceramics (abbreviated as BS-PT) can be quantitatively estimated, whether in electric poling or thermal depoling processes. Experimentally, the correlations between piezoelectric coefficients, electromechanical coupling properties, and non-180° domain reversal percentage are investigated. It is proven that the DPT model provides an effective method for the non-180° domain estimation in rhombohedral crystalline ceramics.

Large deflection analysis of circular piezoelectric micro-actuator with flexoelectric effect

At micro/nano scale, the stiffening effect and flexoelectric effect of strain gradient play important roles in the electromechanical coupling response of piezoelectric micro-components. In this paper, the large deflection bending problem of circular piezoelectric micro-actuator is studied based on the extended linear dielectric theory. In addition to the piezoelectric effect, the flexoelectric effect, the stiffening effect of strain gradient and the high-order electric field effect of polarization gradient are introduced. According to the variational principle, a size-dependent model of circular piezoelectric micro-actuator is established to investigate its electromechanical coupling response. The contributions of piezoelectric effect and flexoelectric effect on large deflection behaviors of piezoelectric micro-actuator are revealed. It is hoped that the research results will be helpful to further understand the electromechanical coupling properties of piezoelectric micro-components and improve the control precision of piezoelectric micro-actuator.

Electro-mechanical coupling properties of band gaps in an elastic/piezoelectric phononic crystal nonlocal nanobeam with periodically attached “spring-mass” resonators

Electro-mechanical coupling properties of band gaps in an elastic/piezoelectric phononic crystal nonlocal nanobeam with periodically attached “spring-mass” resonators

Nonlinear free vibration analysis of ionic liquid enhanced soft composite membrane

Due to their electromechanical coupling properties, ionic liquid (IL)-enhanced dielectric elastomer composites are promising for applications in soft robotics and implantable actuators. However, their structural vibration behaviors subjected to electric fields remain unclear. This work investigates the nonlinear vibration of IL-enhanced soft composite (ILESC) membranes subjected to electric loading through theoretical modeling and numerical simulation. The effective properties of ILESC membrane are determined by a developed micromechanical model considering the physical mechanisms as involved. Governing equations for the nonlinear vibration of a pre-stretched circular membrane made of ionic liquid/poly (dimethylsiloxane) (IL/PDMS) are established, which are solved by Taylor series expansion (TSE) and differential quadrature (DQ) methods. The developed model and numerical results are verified by comparing present results to existing studies and finite element analysis. The influences of the size of the membrane, the direct current (DC) voltage and alternating current (AC) frequency of the electric field, and the attributes of the IL fillers and matrix on the nonlinear vibration of the structure are investigated. The voltage-induced nonlinearity is highly sensitive to the content, size and shape of the IL fillers. The performances of the structure within various AC frequency bands can be tuned by changing the geometry of the IL fillers as well as the surface charge density of the matrix. This study aims to provide guidelines for predicting and optimizing the structural behaviors of ILESC membranes, accelerating their applications in engineering demanding flexibility and voltage-dependent responses.

Study of temperature and frequency dependant dielectric, impedance, AC resistivity, modulus spectroscopy and electromechanical coupling properties of [BaNd0.1Ti0.8Nb0.1O3](1-x)[Na0.5Bi0.5TiO3]x relaxor ferroelectric ceramics

[BaNd0.1Ti0.8Nb0.1O3](1-x)[Na0.5Bi0.5TiO3]x ceramics with x = 0.25, 0.40, 0.60, 0.65 & 0.70 were prepared through solid-state sintering route. In the present study, temperature and frequency dependant dielectric, Impedance, AC resistivity, modulus spectroscopy and electromechanical coupling properties carried out. These materials showed modulus resonance and anti-resonance i.e. electromechanical coupling (M″ vs. frequency). From these modulus resonance and anti-resonance studies piezoelectric charge constant (d33) was obtained. The values of the piezoelectric charge constant (d33) are 3.34 nm V−1, 6.26 nm V−1, 11.58 nm V−1, 14.10 nm V−1 & 10.70 nm V−1 for x = 0.25, 0.40, 0.60, 0.65 & 0.70, respectively. In the present study, the modulus electromechanical was studied in jig with spring which applies constant stress on the ceramic sample. The higher value of electromechanical coupling conversion in the present study may be attributed to this constant applied stress, higher temperature and polarized oxygen vacancies at the crystal lattice at these elevated temperatures (773 K & 873 K).

Conformally Large-Area Single-Crystal Piezocomposites with High Performance for Acoustic Transducers.

Large-area and conformal piezoelectric elements are highly desired for acoustic transducers to possess a large power source level and wide detecting range. To date, single-crystal piezocomposites attract much attention on enhancing the power source level and bandwidth for next-generation acoustic transducers, owing to their higher piezoelectric and electromechanical coupling properties compared to traditional piezocomposites. Unfortunately, it is still challenging to achieve large-area and conformal single-crystal piezocomposites because of the fragile nature, large anisotropy, and the limited grown size of piezoelectric single crystals. Here, we successfully fabricate the conformally large-area single-crystal piezocomposite with an area of 160 × 50 mm2 and a bending angle of 162° by a modified 3D-printing-assisted inserting method. The single-crystal piezocomposite exhibits a high thickness electromechanical coupling factor kt of 85% and a large piezoelectric coefficient d33 of 1150 pC/N, surpassing those of the reported large-area piezocomposites. The influence of the volume fraction and curvature radius of single-crystal PCs and acoustic transducers was investigated. Furthermore, we designed an acoustic transducer based on the conformal single-crystal piezocomposite. Benefiting from the excellent piezoelectric and electromechanical properties of the single-crystal piezocomposite, the transducer indicates a high maximum transmitting voltage response of 171.8 dB. Especially, its bandwidth (-3 dB) achieves 60 kHz with a resonant frequency of 292 kHz, which is about 1.8 times superior to the conformal acoustic transducer based on the ceramic piezocomposite with a similar resonant frequency. This work may benefit the future design and fabrication of high-performance and complex-shape piezoelectric composites as key materials for next-generation transducers.

High piezoelectric and dielectric constant of Fe/In Co‐doped KNN‐based ceramics regulated by lattice distortion

AbstractThe new (0.96‐x)(K0.48Na0.52Nb0.96Sb0.04)O3‐0.04(Bi0.5Ag0.5)ZrO3‐x(Fe2O3‐In2O3) ceramics with high dielectric, and electromechanical coupling properties were designed. In this work, the effect of KNN‐based ceramics lattice distortion (c/a) and microstructure on the electrical properties was explored by varying the doping amount of Fe3+ and In3+. The problem of a large number of oxygen vacancies generated by the volatilization of K and Na can be well solved by introducing Fe3+ and In3+. The bulk density increases significantly and the maximum value is about 4.52 g/cm3.The sample with x = 0.003 has the smallest c/a, and exhibits the best piezoelectric and dielectric properties (d33 = 536 pC/N, εr = 3432 and kp = 55.8 %). Low doping concentration of Fe2O3 is considered a “soft” addition for KNN‐based piezoelectric ceramics. The study of this mechanism provides a new idea to regulate the electrical performance of KNN‐based ceramics.

Textured BiScO3-PbTiO3 piezoelectric ceramics with both high electromechanical coupling factor and high curie temperature

High-temperature piezoelectric devices require piezoelectric ceramics with high Curie temperatures and high-temperature stability of piezoelectric properties to avoid the depolarization of piezoelectric ceramics during application. However, piezoelectric materials with high Curie temperatures usually have restrained piezoelectric properties. Crystallographic orientation via texture engineering is a practicable way to improve piezoelectric performance. Here, we propose a sintering-aid-assisted template grain growth strategy to texture BiScO3-PbTiO3 ceramics to overcome the low orientation issue that challenges the texturing of BS-PT for decades. By judiciously selecting B2O3-CuO as sintering aids, we fabricated highly ⟨001⟩-textured 0.43BS-0.57PT ceramics with Logtering factors >99.0% that possess high piezoelectric coefficients d33 of 474–612 pC/N while maintaining relatively high Curie temperatures of 370–402 °C. Importantly, this work addresses a long-standing issue presented in BS-PT ceramics, i.e., the low electromechanical coupling property of BS-PT ceramics (k33 < 0.70) by improving the electromechanical coupling factor k33 to 81.2%. The newly designed textured BS-PT ceramics are thought to be promising candidates for the design of high-temperature piezoelectric transducers and actuators.

Progress in FEM modeling on mechanical and electromechanical properties of carbon nanotube cement-based composites

Abstract Carbon nanotubes (CNTs) reinforced cementitious composite (CNRC) with excellent electrical and self-sensing properties, which enables it to serve as an intrinsic sensor for structural health monitoring (SHM). However, the requirements of modern industry for accurate calculation and performance design of engineering materials are not met by traditional experimental studies alone. The finite element method (FEM) has the advantages of simplicity of operation, accuracy, and cost-effectiveness, and it has been widely used in the property verification and prediction of various composite materials. In this article, the constitutive model, FEM modeling method, and simulation process of CNRC along with existing model types, innate relations, and model parameters are reviewed, and the corresponding mechanical, electrical, and electromechanical coupling properties of CNRC under different parameters are systematically analyzed by FEM method. By combining different uncertainty parameters and model types, the advantages and disadvantages of FEM for mechanical, electromechanical coupling, and SHM applications of CNRC modeling are explored. The results are in good agreement with those in the existing CNRC experiment, which effectively proves the reliability of the FEM method in CNRC research. This work is important to develop a sound theoretical model verification and performance prediction for early applications in SHM of CNRC.