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In this paper, a coupled piezoelectric/semiconducting model is established and applied to study the effect of arbitrarily-located axial mechanical loadings on electric potential distribution in ZnO nanofiber, and the corresponding energy bands are computed via an eight-band k·p method. Results show that the band gap can be tuned by about 25 meV at band edges and about 200 meV away from band edges. The maximum valance band and minimum conduction band are located at band edges. The good mechano-electric effect of piezoelectric semiconductors and the simulating method presented in this paper can be used in designing novel semiconductor devices. [ABSTRACT FROM AUTHOR]

AbstractThis research paper investigates the complex dynamics of Love wave propagation on a piezoelectric plate situated atop a micropolar elastic half-space having imperfect interface. The study delves into the multifaceted effects of flexoelectricity, micro-inertia, guiding layer thickness, and interfacial imperfection on the characteristics of Love waves. The electromechanical coupling factor which is significant in analyzing SAW device performances is also studied. Variable separable method is used to solve the governing equations and desired solution is obtained analytically. The findings contribute to a deeper understanding of Love wave propagation in complex elastic structures and development of advanced sensors and communication technologies. [ABSTRACT FROM AUTHOR]

This paper introduces a tunable design for an electrically actuated vibrating ring micro-gyroscope. This mechanism contains eight piezoelectric micro-beams attached to the vibrating ring in each drive and sense directions. Employing a full geometric non-linear model for the vibrating ring and accounting for the micro-beam's mid-plane stretching; the mathematical model associated with the present system is obtained. Afterward, utilizing the Hamilton principle together with the Ritz method, the reduced equations of motion are derived. The present results are validated by those available in the literature for simpler systems. A three-dimensional (3D) finite element (FE) simulation was carried out in COMSOL Multiphysics commercial software for the case of static deformation since dynamic simulation imposes great computational costs. Next, in-depth parametric studies emphasizing the effect of piezoelectric actuation are conducted. Finally, reporting guidelines for tuning the present vibrating ring micro-gyroscope, the advantages of the proposed design are addressed. [ABSTRACT FROM AUTHOR]

Our paper deals with a mixed initial-boundary value problem in thermoelasticity of piezoelectric bodies with dipolar structure. It is considered the general case of a thermoelastic body which inhomogeneous and also anisotropic and we add the effect of piezoelectricity. We take into account the main equations and basic conditions of a temperature rate dependent theory which predict the waves propagation with a finite speed. Using some middle conditions imposed on the boundary conditions and initial data, we obtain that our mixed problem admits one solution. A generalized form of the Hamilton's principle is obtained to cover this context. [ABSTRACT FROM AUTHOR]

The principle of piezoelectricity has been used to design the micro-electro-mechanical system-based piezoelectric energy harvester for generating electrical energy from surrounding vibrations. The huge popularity of these energy harvesters (EHs) is due to their small size. This paper designs the EH for the heating, ventilation, and air conditioning system. Different cantilever structures with different shapes of the same fabricated area have been designed and investigated at an excited acceleration of 1 g (9.8 ms−2). The multi-perforated cantilever structure has the better stress distribution within the cantilever structure and generates better output voltage and power than their basic design. The proposed tapered multi-perforated cantilever structure has the least value of the resonant frequency of 98.59 Hz which is 31.13% less than the rectangular cantilever structure. The proposed structure generates the output voltage of 14 V which is 91.78% higher than the basic rectangular cantilever structure. It also generates the average output power of 7.15 µW which is 213.59% higher than basic rectangular cantilever structure. [ABSTRACT FROM AUTHOR]

This paper reviews recent studies conducted on various structural shapes coupled with piezoelectric materials for vibration energy scavenging. We focus primarily on micro and meso-sized geometrical structures designed with piezoelectric transducers to develop harvesters. A comprehensive analogy and contrasts between the reviewed works with regards to their advantages, applicability as well as their demerit are presented. We highlight issues that need to be addressed and potential future research to be conducted. It is hoped that this review will provide useful information in selecting suitable shapes of harvesters for maximum realization of energy from ambient vibration for utilization in various applications. [ABSTRACT FROM AUTHOR]

Piezoelectric quasicrystals have attracted the tremendous attention of researchers for their unique properties. In this paper, the semi-analysis solutions of the functionally graded multilayered two-dimensional decagonal piezoelectric quasicrystal plates are investigated for mixed boundary-value problems. Based on the quasicrystal linear elastic theory, the state-space method is employed to derive the state equations composed of partial differential along the thickness direction. The differential quadrature method is utilized to discretize state variables to satisfy the mixed boundary conditions in the horizontal plane. Different from the conventional propagator matrix, a new propagator relationship is proposed to study numerical instability caused by extensive discrete points. Comprehensive numerical results are shown for the sandwich quasicrystal plate with four different stacking sequences. The numerical results reveal the effect of the functional gradient index factors, and boundary conditions on the electric potential, electric displacements, stresses, and displacements under the mechanical/electric loadings. [ABSTRACT FROM AUTHOR]

This paper details several piezoelectric energy recovery interface circuits that have been widely studied at home and abroad to rectify the AC power generated by piezoelectric energy harvesting devices into DC power for direct utilization or storage, and divides the energy recovery circuits into single-stage, bipolar, and three-stage interface circuits according to the purpose and number of interfaces. According to the different interface circuits, the development history of each interface is introduced in detail, and a preliminary outlook on the piezoelectric energy harvesting circuit is provided for further improvement by related researchers. [ABSTRACT FROM AUTHOR]

This paper proposes a novel finite element model (FEM) that can completely characterize the galloping based piezoelectric energy harvester (GPEH) systems. The challenges faced by conventional analytical models in explaining the complex nonlinear dynamics of GPEHs are completely resolved. The present system consists of a cantilever beam with two piezoelectric patches and a square prism attached at the end. A FEM code, in MATLAB environment, is developed to solve the proposed model, and the solutions are compared with the experimental and analytical results from the literature. The lateral galloping force coefficient is represented by a 7th order polynomial based on the quasi-steady theory ensuring highest precision (proved in literature). The results from the present model are found to be in a good agreement with the experimental values, and the accuracy is better compared to the analytical solutions at low wind speeds (<2.5 m/s). The position of maximum efficiency lies near to the onset speed of galloping (2–3 m/s) and the magnitude decreases with further increase in the wind speed. The present work emphasizes the importance of FE (numerical) solution over the conventional analytical ones, and hence will open a door to explore new numerical models in this area. [ABSTRACT FROM AUTHOR]

In this paper, we are concerned with a time-dependent transmission problem for a thermo-electric-magneto-elastic solid immersed in an inviscid and compressible fluid. It is shown that the problem can be treated by the boundary-field equation method, provided an appropriate scaling factor is employed. Based on estimates of variational solutions in the Laplace-transformed domain, we obtain the properties of corresponding solutions in the time-domain without having to perform explicit inversions of the variational solutions in the Laplace-transformed domain. [ABSTRACT FROM AUTHOR]

A multi-component measurement system centred on piezoelectric force sensor is an important mechanical measurement device, in which the piezoelectric sensor is mainly composed of force-sensitive components. The force-electric conversion performance of quartz wafer containing seed crystal and quartz crystal wafers is the main issue of the research in this paper. In the way of microscopic imaging and X-ray diffraction spectrum analysis, based on macroscopic physical properties of crystals, the theoretical basis of piezoelectric effects and the Neumann principle of elastic mechanics, both kinds of crystals have the same matrix of positive piezoelectric effects. Through static and continuous loading tests on quartz wafer containing seed crystal and ordinary quartz wafer, the maximum deviation of the electric charge, respectively, generated by X0° and Y0°cut type seed crystal wafers and ordinary quartz wafer in the static test under the same vector force loading is finally obtained, both seed-containing wafer and ordinary quartz wafer have excellent linearity. In continuous loading test, seed-containing wafer also has good continuous loading performance and can maintain a stable charge output under quasi-static input. Therefore, it is concluded that seed crystal wafers can also be used for actual testing. [ABSTRACT FROM AUTHOR]

In this paper, we analyze acoustic wave propagation in anisotropic fluids and solids. By formulating the acoustic system as an evolution equation over a Hilbert space, we obtain global in time solutions when the associated material parameters are bounded and measurable. In particular, we prove well-posedness of a Cauchy problem for wave propagation in piezoelectric crystals. We then provide a stability analysis of these solutions not assuming positive definiteness of the stress–strain tensor or the piezoelectric stress tensor. Finally we prove continuous dependence on initial data, allowing the piezoelectric tensor to depend on space and time, provided solutions belong to an appropriate function space. [ABSTRACT FROM AUTHOR]

This paper investigates the thermo-electro-mechanical effects in the nonlinear response of piezoelectric laminated plates exposed to thermal and/or mechanical fields. The mechanics incorporate a) the direct piezoelectric effect through the coupling between electric-mechanical fields, b) the pyroelectric effect through the coupling between electric-thermal fields, and c) the geometric nonlinear effects due to large rotations and initial stresses. Building upon the nonlinear multifield mechanics an eight-node plate finite element is developed to discretize the generalized coupled nonlinear equations, which are subsequently linearized and iteratively solved, using the Newton-Raphson technique. Numerical evaluations demonstrate the capability of the present model to capture both of direct piezoelectric and pyroelectric effects in the nonlinear electromechanical response of piezoelectric composite plates, exposed to thermal and/or mechanical fields. The influence of direct piezoelectric and pyroelectric effects on thermal buckling and postbuckling response of various piezocomposite plates, is investigated. The possibility of pyroelectric effect to promote thermal buckling of piezocomposite plates with attached sensor patches is also quantified. The influence of thermo-electro-mechanical effects on the nonlinear response of smart composite plates, subject to either uniform or gradient temperature variations is finally illustrated. [ABSTRACT FROM AUTHOR]

C-eigenvalues and C-eigenvectors of piezoelectric-type tensors play an important role in the piezoelectric effect and the converse piezoelectric effect. In this paper, with the help of components of general C-eigenvectors, we present a new class of inclusion sets to locate all general C-eigenvalues for a given general piezoelectric-type tensor. Finally, numerical examples are reported to be tighter than some existing results. [ABSTRACT FROM AUTHOR]

The main goal of this paper is to develop a mathematical model for the piezoelectric elastic-semiconductor medium. The medium is homogeneous and isotropic that is exposed to photothermal excitation processes. Gauss's law of electrostatics is used to obtain the effect of the piezoelectric phenomenon. The governing equations with the electric potential are expressed in terms of thermoelasticity theory and photothermal theory. One-dimensional Laplace transform is used to get the solution of some physical quantities when the heat sources and body forces are absent. The mechanical forces and thermal loads are used to get the analytical solution of physical quantities under investigation. The inverse Laplace technique with a numerical method is employed to obtain the solution in the time-physical domain. A novel parameter depends on pyro-electric moduli is presented. Some numerical results are illustrated and shown graphically. [ABSTRACT FROM AUTHOR]

The paper reports on the piezoelectric performance, electromechanical coupling and related energy-harvesting figures of merit of three forms of 1–2–2 composites based on domain-engineered single crystals. The effect of the single-crystal piezoelectric properties and elastic properties of the laminar polymer matrix on the appropriate figures of merit of the composite is studied. The main active components of the studied composites are [0 0 1]-poled perovskite-type single crystals with chemical compositions: 0.92Pb(Zn1/3Nb2/3)O3–0.08PbTiO3, 0.67Pb(Mg1/3Nb2/3)O3–0.33PbTiO3 and [Lix(K1−yNay)1−x](Nb1−zTaz)O3: Mn, where x = 0.06, y = 0.1–0.3, z = 0.07–0.17, and the level of Mn doping is 0.25 mol. %. Examples of non-monotonic volume-fraction dependences of the piezoelectric properties, figures of merit and anisotropy factors are analysed. New diagrams are first built to demonstrate the volume-fraction regions where a large anisotropy of the piezoelectric coefficients d3j* and electromechanical coupling factors k3j* is achieved, and where energy-harvesting figures of merit of the composite are at least five times larger than analogous parameters of single-crystal components. The studied 1–2–2 composites are of interest as anisotropic materials with high piezoelectric sensitivity and large figures of merit which are important for sensor, energy-harvesting and related applications. [ABSTRACT FROM AUTHOR]

Anti-plane shear wave propagation in a functionally graded piezoelectric substrate and a piezoelectric substrate guided by a slit is analyzed theoretically. The equations of motion are taken from the linear theory of piezoelectricity for polarized ceramics. The dispersion relation is obtained by applying appropriate boundary conditions on the derived solutions. PZT-5 and ZnO are taken as numerical examples to manifest the effect of different material parameters (gradient factor, slit width etc.) graphically on the phase and group velocity of the considered wave. $ \textrm{LiI}{\textrm{O}_\textrm{3}} $ LiI O 3 and $ \textrm{BaTi}{\textrm{O}_\textrm{3}} $ BaTi O 3 materials are taken separately to compare the results. Also, graphs are plotted for different modes of the wave as well as for different frequency ranges and for the case when slit is absent. As a special case, it is remarked that the present study has resemblance with one of the existing works. The highlights of the study are to characterize the anti-plane wave propagation within a functionally graded piezoelectric substrate/gap/piezoelectric substrate coupled structure, to show the effect of different parameters, modes, frequency, etc. on the velocity profile of the considered wave and to show the effect of gap layer. The outcomes of this study may be used to enhance the sensitivity of acoustic wave devices and sensors. [ABSTRACT FROM AUTHOR]

In this article, the effect of thermal shock on one end of a one-dimensional piezoelectric material has been discussed. The governing equations are formulated in terms of stress, temperature, displacement, and electric potential based on the Green–Lindsay theory of generalized thermoelasticity. The Laplace transformation has been used for non-dimensional coupled equations. The reduced equations are written in vector–matrix differential form and hence solved using the state–space approach method. Finally, the inverse Laplace transformation has been obtained numerically and its graphical representation has been discussed. It is shown that the temperature distribution and displacement distribution propagate with finite speed under the Green–Lindsay theory, whereas the speed of propagation of electric displacement and the electric potential is infinite. Also, it is noted that the temperature is maximized where the initial thermal load applied. [ABSTRACT FROM AUTHOR]

In this study, the frequency and capacitance of piezoelectric materials due to compressive stress were analyzed, and the overall material properties (compliance matrix, piezoelectric charge constant and dielectric constant) of piezoelectric ceramics were optimized using parametric estimation methods. The piezoelectric ceramic used for optimization was KICET-PZT8, and the compressive stress was applied from a stress-free condition up to 50 MPa. As a result, with increasing compressive stress, the values of $s_{11}^E$ s 11 E , $ - s_{12}^E$ − s 12 E and $s_{66}^E$ s 66 E tended to increase, while $ - s_{13}^E$ − s 13 E and $s_{33}^E$ s 33 E increased and then decreased at 20 MPa or higher. $ - {d_{31}}$ − d 31 and ${d_{33}}$ d 33 showed the maximum values at 40 MPa of compressive stress, with the values reaching 147 pC/N and 375 pC/N, respectively. These values were analyzed to have increased by 117% and 115%, respectively, compared to the stress-free condition. Additionally, the dielectric constant ($\varepsilon _{33}^T$ ε 33 T ) was found to increase linearly with the applied compressive stress. The understanding of the changes in piezoelectric properties under various compressive stresses derived from this study is expected to be applicable in various ways for the design and application of piezoelectric devices using compressive stresses, including BLT. [ABSTRACT FROM AUTHOR]

The field of III-nitride (InGaN) nanowire micro light-emitting diode (µ-LED) displays is rapidly expanding and holds great promise, thanks to their chemical stability and outstanding performance across the entire visible spectrum. Notably, III-nitride (InGaN) nanowires, free from compositional substitutions, dislocations, and piezoelectric polarization effects associated with lateral strain relaxation with large surface-to-bulk-volume ratio, are advantage-missing in traditional planar counterparts. This comprehensive overview examines the potential landscape, associated challenges, strategies to overcome them, and opportunities for the development of advanced µ-LED displays with vibrant and accurate color representation, contributing to the advancement of next-generation display technologies. This study also covers the current obstacles faced by III-nitride (InGaN) nanowire-µ-LED displays and possible solutions to address them. [ABSTRACT FROM AUTHOR]

Today, electric and electronic equipment has become more prominent in almost every economic sector, scientific research, and everyday life. The purpose of this equipment is to enable military operations to be more efficient and effective. This equipment's main problem is its autonomy, which is dependent on an electric power source: even if it has batteries or other energy storage sources, these need charging, and their storage capacity is usually proportional to their weight. Weight can negatively affect a foot soldier's agility and reduce his operational capacity when carrying batteries. In piezoelectric generators, mechanical energy is converted into electrical energy, allowing dissipated kinetic energy to be converted into electricity. This dissertation presents a prototype piezoelectric generator integrated into a boot. It can charge electronic equipment and electric devices carried around by military personnel. According to the prototype, an AAA battery can be charged in approximately seven million steps by generating 80 kJ of energy per step. Even though the isolated prototype cannot be used to power the equipment of a military on foot, it can be combined with other forms of electrical power for the same purpose or for enhancing the autonomy of emergency systems such as those that detect man overboard. The components of a piezoelectric generator were identified and explored through analyzed work by several researchers. An electrical power supply for military electrical and electronic equipment was developed by incorporating a piezoelectric generator into a boot using the knowledge acquired during the study. [ABSTRACT FROM AUTHOR]

Batteries with a limited lifespan have gradually failed to meet the development needs of some low-power electronic products. Harvesting wind energy to power the above devices has been a promising way. Facing the time-varying characteristics of wind direction and velocity in the natural environment, an efficient orientation-adaptive energy harvester (OAEH) based on the piezoelectric effect is proposed. An experimental test system is established to probe into the output and adaptive performances of the OAEH. The experimental results indicate that improving the inertia of the tray can abate the initial wind velocity and enhance the output power to a certain extent. The relative deviation (γ) of power integration areas at different inclinations is less than 3%. The harvester has 364.86% enhancement in average power integration area comparing that with the fixed shaft. Besides, the OAEH can drive a monitoring device with a display screen and integrated sensors, which can be utilized to monitor the condition of the bridge, flyover, and so on. [ABSTRACT FROM AUTHOR]

The present research article manifests the dissipation and dispersion characteristics of Love-type waves in a flexoelectric-piezoelectric/functionally graded piezomagnetic material structure, loaded with Newtonian liquid. The interface between the piezoelectric plate and the piezomagnetic substrate is considered mechanically and electromagnetically imperfect. Transcendental complex dispersion relations for electrically and magnetically open and short cases are obtained by rigorous analytical methods. A particular numerical example is considered and dispersion, as well as attenuation curves are obtained for it. Influences of mechanical and electromechanical imperfections, flexoelectricity, layer-thickness, and material gradient parameters on phase velocity and attenuation of Love-type waves are meticulously examined. [ABSTRACT FROM AUTHOR]

Polyvinylidene fluoride (PVDF) electrospun scaffolds have recently been developed for cardiac tissue engineering applications thanks to their piezoelectricity. However, PVDFs' hydrophobic nature requires modifications by incorporating natural polymers. In this study, we focussed on the hybrid electrospinning of PVDF and gelatine and the further introduction of graphene oxide nanoparticles to investigate either hydrophilicity or piezoelectricity enhancement and its impact on mouse embryonic cardiomyocytes. The results revealed a nanofibre diameter of 379 ± 73 nm for the PVDF/gelatine/graphene oxide (PVDF-GO-CG) platform, providing excellent tensile strength. Additionally, hydrophilicity was improved by gelatine and GO incorporation compared with pure PVDF. Cellular studies also showed an elongated morphology of cardiomyocytes, similar to the myocardial tissue, as well as high viability and non-toxicity in the PVDF-GO-CG scaffold according to the average survival rate. Furthermore, the expression of connexin 43 and troponin T genes underwent an increment of 41 and 35% in the PVDF-GO-CG compared with the PVDF-CG sample. This study proves the applicability of the PVDF-GO-CG scaffold as an alternative substrate for developing engineered cardiac tissues by providing an environment to re-establish their synchronised communications. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The sensitivity analysis of the anisotropic properties for PZT-4 and PZT-5 have been performed using the complex variable finite element method (ZFEM) on a two-dimensional geometry. A thin film model is subjected to a uniform boundary load to induce mechanical strain yielding variations in the electric potential field. The numerical results from mechanical displacements and electric potential fields are verified against the solution from a commercial software. The first order derivatives obtained from ZFEM illustrate the sensitivity of material properties as design parameters for real time tunability of additive manufacturing processes. Results show that the largest sensitivities for the direct piezoelectric effect emerge from C 33 and the elastic anisotropic coupling of normal and shear stresses through coefficient C 13 followed by the dielectric and piezoelectric constants in the poling direction. [ABSTRACT FROM AUTHOR]

In this study, energy harvesting from nonlinear vibrations of a functionally graded plate with bonded piezoelectric patch under moving loads and moving masses is investigated. The coupled nonlinear system of equations are derived using the generalized Hamilton's principle considering both the geometrical nonlinearity and the nonlinear electromechanical coupling. Then, the equations are solved using finite element method and Newmark time integration scheme. For a case study, the effects of different parameters such as piezoelectric patch thickness, location of piezoelectric patch, different boundary conditions, and different width of plate on harvested power and the plate's nonlinear vibration are investigated. This article is motivated by the lack of published studies on nonlinear distributed piezoelectric energy harvesters under moving loads (masses). [ABSTRACT FROM AUTHOR]

In this work, we studied the piezoelectric hysteresis effect induced by a weak dc electric field in ferroelectric ceramics. Precision measurements of the impedance spectra for the thickness vibrational mode of thin piezoceramic disks at different polarities of applied dc electric field were performed using the method and program of piezoelectric resonance analysis (PRAP). The field dependences of the complex piezoelectric constants of piezoelectric ceramics obtained by processing successively measured impedance spectra were analyzed and a physical interpretation of the results was proposed. [ABSTRACT FROM AUTHOR]

Road piezoelectric energy harvesting based on the piezoelectric effect is a green energy utilization concept, which converts mechanical energy into electrical energy. Because of favorable properties such as low carbon significance, this technology caters to widespread applications. The major limitation of this concept is the fatigue degradation of piezoelectric transducers under long-term traffic loads, which subsequently reduces the energy conversion efficiency. Moreover replacing piezoelectric harvesters through road surface reconstruction will incur high costs and damage the integrity of road surface. With regard to the aforementioned factors, this study presents a polarization method for on-site road conditions from the perspective of the recovery and maximizing the piezoelectric energy harvester. First, the polarization of piezoelectric layer under simulated on-site road conditions was tested in a laboratory. The test results show that better transducer repolarization effect is observed when the polarization temperature is greater than 120 °C, the polarization time is less than 30 min, the polarization voltage is 2 kV/mm (greater than 1.2 kV/mm), and the d33 reaches 314 pC/N. Then, for an excitation frequency of 10 Hz and a test displacement of 1 mm, the piezoelectric harvester unit, which is based on the polarization method for on-site conditions, is used for piezoelectric performance test. The maximum output voltage of the polarized piezoelectric energy harvester is 10.47 V, which is 81.79% that of the initial polarization harvester in the indoor environment. The study proposes a polarization system under on-site conditions for road piezoelectric energy harvester and its equipment construction method, along with the future recycling processing applications after the road piezoelectric energy harvester reached the service life of the road. [ABSTRACT FROM AUTHOR]

In the present work, the development and analysis of linear piezoelectricity in the peridynamics framework is presented. The model is developed using non-ordinary state-based Peridynamics. The equations of motion are derived using Hamilton's principle and the correspondence material model is developed by establishing the connection between the classical theory of linear piezoelectricity and the newly proposed peridynamic linear piezoelectricity framework. An implicit implementation is proposed for two-dimensional linear piezoelectricity. Moreover, for the stabilization of the proposed scheme, the bond-associated correspondence model is used. We demonstrate the capabilities of the proposed model by presenting some 2 D numerical examples. [ABSTRACT FROM AUTHOR]

Piezoelectric devices belong to the most prominent examples of smart materials. They find their applications in sensors and actuators, e.g. in the context of ultrasonic applications, tomography, cavitation-based cleaning. Nowadays, the design of new piezoelectric devices is generally accompanied by a computer-aided design, i.e. some models are used to predict the mechanical–electrical coupling of the new products. The coupling is described by a set of second-order coupled partial differential equations. For the mechanical part, this system comprises the equation of motion for the mechanical displacement in three dimensions and for the electric part, an electrostatic potential equation is employed. Coupling terms and an additional Rayleigh damping approach ensure the validness of the model. In this work, we analyze the existence, uniqueness and regularity of the solutions to these equations and give a result concerning the long-term behavior. The assumptions mainly on the material parameters involved are quite natural and allow meaningful physical interpretation. [ABSTRACT FROM AUTHOR]

Flexoelectric polarisation in liquid crystalline elastomers with wedge-shaped mesogens was investigated. Flexoelectric polarisation was fixed in the elastomers that were cross-linked under uniaxial deformation with splay distortion. X-ray diffractometry revealed that the orientational order partially remained at about S = 0.2 even in the temperature region of the isotropic phase designated tentatively as the pseudo-isotropic phase. The electric charge caused by polarisation due to the flexoelectric effect was estimated to be −809 pC/mm2 in the splay distorted liquid crystalline elastomers, whereas almost no electric charge was detected in the uniaxially and uniformly aligned elastomers. We tentatively conclude that the macroscopic polarisation due to flexoelectric effect emerged and was fixed in the liquid crystalline elastomers by cross-linking under splay distortion. [ABSTRACT FROM AUTHOR]

An interface crack in 1D piezoelectric quasicrystalline space is considered. Both conducting and mixed conducting-permeable electric conditions at the crack faces are studied. The matrix–vector representations of the phonon, phason and electric quantities via the sectional-holomorphic function are derived. Two types of electrical conditions at the crack faces are considered – conducting case and mixed conducting-permeable case. A Riemann problem of linear relationship and a combined Dirichlet–Riemann boundary value problem are derived. Exact analytical solutions of the mentioned problems are presented and the simple analytical formulas for all required values are given and numerically illustrated. [ABSTRACT FROM AUTHOR]

The complex process of wound healing depends on the coordinated interaction between various immunological and biological systems, which can be aided by technology. This present review provides a broad overview of the medical applications of piezoelectric and triboelectric nanogenerators, focusing on their role in the development of wound healing technology. Based on the finding that the damaged epithelial layer of the wound generates an endogenous bioelectric field to regulate the wound healing process, development of technological device for providing an exogenous electric field has therefore been paid attention. Authors of this review focus on the design and application of piezoelectric and triboelectric materials to manufacture self-powered nanogenerators, and conclude with an outlook on the current challenges and future potential in meeting medical needs and commercialization. [ABSTRACT FROM AUTHOR]

Multifunctional motion sensors have broad applications in the field of the internet of things (IoT). An octopus-shaped self-powered motion sensor is proposed to monitor the acceleration, motion direction, rotation speed and angle of objects. The charge transfer analysis of the sensor is carried out based on the positive piezoelectric effect, contact electrification effect and electrostatic induction. The influence of the surface microstructure and doping ZnO on the sensor sensitivity is investigated, and the improved film increases the sensor sensitivity by 13.58%. It is found that the output voltage decreases as the frequency increases. At the same frequency, the sensor output voltage amplitude is proportional to the acceleration amplitude. The test results show that the sensor can identify the motor rotation speed and angle, and the linear running direction and the motion state of the sweeping robot. Furthermore, the proposed sensor is cheap and beneficial for large-scale use. [ABSTRACT FROM AUTHOR]

With the development and applications of nano-electro-mechanical systems, academic interest in the mechanical behavior of piezoelectric structures at nanoscale is increasing. Interesting unconventional phenomena have been observed either experimentally or through molecular dynamics simulation. The most common and also important one is the size-dependent characteristics. Classical continuum mechanics with necessary modifications has been proven to be very powerful in explaining these particular characteristics in a relatively simple theoretical framework. This article reviews the recent advances in understanding the size-dependent dynamic responses of piezoelectric nanostructures from the viewpoint of modified continuum mechanics. Particular attentions are paid to three advanced theories of piezoelectricity (e.g. gradient piezoelectricity, surface piezoelectricity, and nonlocal piezoelectricity) and their abilities to predict unconventional vibration and wave characteristics in piezoelectric structures and devices at the nanoscale. The article could serve as a useful reference for the future research on or design of nanostructures with multifield couplings. [ABSTRACT FROM AUTHOR]

An electromechanical coupling model for the thickness shear vibration of a size dependent quartz crystal plate with mass loading is established from the Hamilton's principle and the modified couple stress theory. The influence of couple stress or size effect on frequency shift and average mass sensitivity of the sensor is studied by numerical examples. The results show that couple stress or size effect can increase the frequency shift and improve the mass sensitivity as well. The thinner the quartz plate, the more significant the size effect on the frequency shift, and the more beneficial it is for mass sensing. Moreover, for very thin quartz plate and large mass ratio, ignoring piezoelectricity will cause large error of frequency shift. But this error will decrease due to the dominant role of size effect when the sensor is thin to a certain thickness. [ABSTRACT FROM AUTHOR]

Radiations of atomic/nuclear particles during earthquakes have been detected and verified by many experiments. Some tests also verify some radiations during the fracture of small-size piezoelectric rocks in the laboratories. Some researchers studied the mechanism of such reactions and considered the photonuclear reaction as a possible mechanism for such phenomena. In this study, to understand the dominant mechanisms of radiation of particles before or during the earthquakes and also to find some relationships between applying the mechanical energy and the mentioned radiations in small and giant scales of piezoelectric rocks, we first analyzed the piezoelectricity equations in these rocks. Then, we performed an energy analysis of the earthquakes, considering the amount of energy stored in a block of rock during applying the uniaxial stress. Thereafter, MCNPX simulation code is employed to simulate the tracks and energies of the created particles in a small piece of quartz and in three giant granite blocks. We have found that in the small piece of quartz, the atomic interactions cause low-energy electrons' and photons' radiations, and no nuclear interactions have been observed. However, in giant granite blocks, in addition to the atomic interactions, the photonuclear reactions play big roles, resulting in the creation of high-energy photons, neutrons and protons. Furthermore, some equations have been extracted to relate the mechanical energy stored in a piezoelectric rock and the number and energy of the created atomic/nuclear particles. The outcome of this research would be very beneficial in understanding the earthquake mechanism and its prediction. [ABSTRACT FROM AUTHOR]

A comparative study of Love-type wave vibrations in a distinct piezoelectric (PE) material thin film with a highly and weakly dielectric interface with an elastic pre-stressed elastic plate is investigated analytically. Using the PZT-2, PZT-4, PZT-5H, LiNbO3 and BaTiO3 numerical data for the PE material, we achieved significant outcomes of PE and flexoelectric effect in the study. Dispersion equations are achieved analytically for both electrically open and short cases together with highly and weekly conducting interfaces in the transcendental complex form. Outcomes specify that microstructures having flexoelectricity has a significant influence on dispersion features. The existence of flexoelectricity shows that complex phase velocity with a positive imaginary part increases the phase velocity of considered waves with time. Numerical results are highlighted graphically and validated with existing results. The present study is a prior attempt to show the flexoelectricity influence with weekly and highly conducting interfaces and also to show that the outcomes are significant to obtain better surface acoustic wave device's performance. [ABSTRACT FROM AUTHOR]

The experimental and simulation of dielectric, AC resistivity and dielectric resonance and anti-resonance data on (Na0.5Bi0.5)(NdxTi1-2xNbx)O3] ceramics were carried out using modified Lorentz equations as proposed by us instead of well know and generally applied laws like Arrhenius law and formulas on piezoelectricity to obtain activation energy, relaxation time, piezoelectric charge constant and voltage constant directly from the experimental data. The piezoelectric charge constant (d33) evaluated from the modeling are 864.64 p.m/V and 122.40 p.m/V; whereas the piezoelectric voltage constant (g33) are 10.88 p.m2/C and 8.55 p.m2/C for x = 0.0125 and 0.025 ceramic samples, respectively. [ABSTRACT FROM AUTHOR]

This special issue presents a collection of works on flexible electronics including material development, device design and engineering. An interesting contribution from Prof. ZHOU's group [[5]], Xiamen University, P.R. China, reports the fabrication of capacitance sensor and describes its application in human acoustic monitoring. The field of flexible electronics has received tremendous development in recent years, shaping our society from personal life to industry and to national security. [Extracted from the article]