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The object of the study is flexible piezoelectric bimorphs of rod and membrane types, consisting of two or more homogeneous piezoelectric layers (films) of equal thickness with the same or opposite-directional polarization, interlayer, and external electrodes (are electrode coatings). The solution of the actual problem has been considered: increasing the operating characteristics of flexible piezoelectric bimorphs for more efficient use as generators of electric energy, sensors, and actuators—converters of control electrical signals into movement of working surfaces for manipulating or assembling microscale objects. The regularities of the influence of the magnitude of the initial longitudinal load applied to the ends of a bimorphic rod or uniformly distributed along the outer circular contour (perimeter) of the bimorphic round membrane on the resulting performance values for flexible piezoelectric bimorphs of the rod and membrane types, respectively, have been investigated. We believe that the magnitude of the longitudinal force applied to the movable end of the rod bimorph or to the outer perimeter of the membrane does not change over time and does not exceed the corresponding value of the strength of instability considering the cantilever or hinge fastening of the bimorph. Therefore, we have variable multidirectional bending directions of the bimorph (actuator) when an alternating control electric voltage is applied to the electrodes, i.e., when the sign of the control electric voltage is changed, the direction of bending (blocking force) also changes to the opposite one and after "switching off" the control electric voltage, the bimorph returns from the curved state to the original rectilinear one. Analytical solutions have been obtained for the deformation fields: deflections and angles of rotation of working cross sections of flexible piezoelectric bimorphs using the well-known "hypothesis of flat sections" and the method of Mor's integrals in Mechanics of Materials. The effect of increasing the resulting deflections and blocking forces of flexible piezoelectric bimorphs because of the action of the initial compressive load has been identified and studied. The results of numerical modeling have been obtained for a flexible rod bimorph made of PZT piezoceramic layers, the effective deformation characteristics of which were determined by solving the reverse problem on the basis of the results of other authors. The cases of cantilever and hinge fastening of the ends of the rod bimorph have been considered. It has been found that the magnitude of the blocking force for the bimorph in the form of a hinged rod significantly exceeds that for the bimorph in the form of a cantilever, while the action of the longitudinal compressive force linearly increases the magnitude of the deflection and blocking force of the bimorph. [ABSTRACT FROM AUTHOR]

The generation of microactuation using narrow thermal hysteresis Ti-Ni-Cu shape-memory alloy films deposited on non-metallic substrates as the active element is studied based on a model previously developed for Ni-Ti/Si bimorphs. To this end, the compositional range in which the B2 (monoclinic) → B19 (orthorhombic) martensitic phase transformation occurs was considered, and films were deposited by magnetron sputtering on heated Si and Kapton substrates. Ultra-fine grains were observed for the 550 °C deposition temperature. The selected composition was close to Ti50Ni35Cu15, so the narrowing of the thermal hysteresis is not associated with a significant reduction in shape recovery capability. The microstructure and composition of the target materials and as-deposited films used in our experiments were characterized by X-ray diffraction and scanning electron microscopy, whereas the temperature dependence of the volume fraction of the martensite phase was derived using differential scanning calorimetry records for the target materials and from the temperature dependence of the electrical resistance data for the films. An original model was used to predict the actuation of cantilever-type bimorphs with Kapton and Si substrates. [ABSTRACT FROM AUTHOR]

One of the key requirements for MEMS speakers is to increase the sound pressure level (SPL) while keeping the size as small as possible. In this paper we present a MEMS speaker based on piezoelectric bimorph cantilevers that produces a higher SPL than conventional unimorph cantilever speakers. The active diaphragm size is 1.4 × 1.4 mm2. The bimorph cantilevers are connected in parallel to make full use of the actuation voltage. At 1 kHz, the measured SPL reached 73 dB and the peak SPL reached 102 dB at the resonance frequency of 10 kHz in a 711 ear simulator under a driving voltage of 10 Vrms. The total harmonic distortion of the MEMS speaker was less than 3% in the range from 100 Hz to 20 kHz. Although the absolute SPL was not the highest, this work provides a better SPL for all piezoelectric MEMS speakers. HIGHLIGHTS: • This work presents a piezoelectric MEMS speaker with bimorph cantilevers. •The piezoelectric MEMS speaker in this work is made from AlN instead of PZT. •Bimorph speakers have a higher sound pressure level than the commonly used unimorph speakers. [ABSTRACT FROM AUTHOR]

To convert as much vibration energy as possible into electrical energy, the design of a high-performance piezoelectric vibration energy harvester (PVEH) has been studied widely in recent years. To overcome the low energy utilization of a traditional piezoelectric cantilever by inhomogeneous strain, a uniform stress distribution of bimorph by an ARC mechanical stopper structure has been designed for maximum piezoelectric vibration energy harvesting. Deflection equations and their simulation at the first-order modal of two classic bimorph cantilever beam models, with transverse tip force and with equal curvature, are derived based on the Euler–Bernoulli beam assumption. Piezoelectric energy from a beam model with equal curvature is four times that of a cantilever beam model with transverse tip force at the theoretical level. The nonlinear frequency response performance of bimorphs by an ARC mechanical stopper and point stopper model could be observed by the numerical simulations of the lumped parameter electromechanical model. PVEH prototypes were manufactured by 3D printing and tested. To verify the high-power generation capacity, PVEH with an ARC stopper has 1.756 times more voltage than that of a PVEH with a point stopper. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to present a new stand developed for exeprimental testing of a tremor compensation system with bimorph piezoceramic actuators using optical methods. The characterization of the bimorphic actuators was performed by plotting the response curve, for displacements between 0 and 150 V. A new method for determining the response curve has also been developed, using optical image capture and processing. Comparing the results obtained using the optical method with those obtained by manual reading the measurements, it was found that similar results were obtained, relative to the type and maximum deflection of the tested actuators, which validates the new optical developed method by ICPE-CA. [ABSTRACT FROM AUTHOR]

The quality of collected electric power is directly affected by the mechanical properties of piezoelectric cantilever, which is an important part of vibration energy collection system. A piezoelectric energy harvester is employed to study the electromechanical conversion performance of piezoelectric cantilever under different counterweights by adding mass blocks. An experimental platform is built to test the piezoelectric energy harvester based on numerical analysis. The effects of different mass attached to the cantilever on frequency bandwidth and phase angle difference are studied. The numerical analysis indicates that the output voltage of the two piezoelectric bimorphs in series is higher than that of the single piezoelectric plate, and the natural frequency of the structure changes little. The mass is the main factor affecting the resonant frequency and output voltage of the energy harvester based on the expression of natural frequency. The experimental results show that the maximum output voltage increases by 39.42% and the natural frequency decreases by 13.83% when the mass ratio is 11.75%, which is consistent with the numerical results. The increasing of counterweight causes the decrease of third-order natural frequency of piezoelectric cantilever and the increase of frequency bandwidth. It is demonstrated that the phase difference decreases rapidly and finally approaches to − 180° when the external excitation frequency is near the resonant frequency. The phase difference at the peak is close to zero when the mass ratio is 11.75%, corresponding to the highest voltage output. The results have reference significance for the system adaptive tuning of vibration energy harvester. [ABSTRACT FROM AUTHOR]

Purpose: The steady-state parametric analysis of a piezoelectric-coupled rotating tapered-bimorph system consists of a central host beam and two piezoelectric ceramic patches above and below it, tapering along positive X-direction and rotating in the X–Y plane, subjected to axial dynamic as well as static loading at its one end is done. The influence of three boundary conditions and various system parameters are also studied. Methods: The mathematical modeling of the rotating tapered-bimorph system is formulated with the help of Hamilton's equation. The parametric analysis of the axially loaded system is done for clamped-free (C-F), pinned-pinned (P-P), and clamped-pinned (C-P) boundary conditions. A number of parametric instability regions along with static buckling load plots are obtained and analyzed for various values of the piezoelectric patches to the host beam thickness ratio, taper parameter, and rotational frequency using MATLAB software and depicted through a series of diagrams. Results: The results illustrate that the principal modal frequencies of the tapered-bimorph rotating system are increased rapidly with an increase in the thickness ratio, whereas increase less significantly with a rise in taper parameter and spinning speed for both the static and dynamic loading conditions. Conclusion: The lowest first modal frequency is observed for the P-P system under any given system configurations and operating conditions, which can be used for low-frequency rotational vibration energy harvester over the orthodoxly used C-F system. Designing low-frequency rotational vibration energy harvester and rotor blades can be done by selecting appropriate dimensions and parameters presented in this article. [ABSTRACT FROM AUTHOR]

We have theoretically and experimentally demonstrated the greatly enhanced energy harvesting property of the specific magnetoelectric (ME) device, comprising a piezoelectric bimorph cantilever with a permanent magnet tip mass based on a compound interaction between the remanent magnetic moment of the magnet and a nonuniform alternating magnetic field. With appropriate positioning of the device, the coexistence of torque-mode and force-mode excitations leads to reinforced magneto-mechanical coupling, which subsequently yields improvements in both ME response and power conversion. In the experiments, a piezoelectric bimorph/magnet energy harvester was placed at a distance of 10 mm from a power line that was conducting a 50 Hz, 10 A current, and a maximum power of 2.136 mW was achieved via the optimal cooperative magnetic coupling mode. This output power is 7.8× larger than that produced using the conventional torque mode. [ABSTRACT FROM AUTHOR]

A unique strategy of low-frequency wideband vibration control by harnessing the concept of feedback control between the piezoelectric bimorph sub-cells which are acting as sensors and actuators is conceptualized in this paper. In the unit cell, voltages from the sensing bimorph are fed back to actuate another bimorph through operational amplifier-based gain circuits. The prime novelty of the paper is the non-trivial formulation of the spectral element of the non-reciprocal piezoelectric beam (NRPB), having electro-mechanically coupled sensing and actuating bimorph in the unit cell, derived from the exact solution of the governing differential equations. The analytical formulation employing the spectral element method enables the elementary assembling of the NRPB units to simulate different boundary conditions and various configurations arising due to the alteration of the position of the sensing and actuating bimorph. The direct frequency responses for various configurations are obtained for a cantilevered and a simply-supported beam with varying feedback gain. The feedback gain induced damping to the system, hence sharp peaks and drops are flattened. Most promisingly, the amplitude of the displacement response for the entire frequency range can be brought down below its corresponding static deformation with the application of positive gain for certain configurations. Hence, the proposed system could potentially be used for application in the field of vibration and acoustics. • Emergence of superior vibration control by non-reciprocal piezoelectric beam (NRPB). • Realization of the constant gain sensing and actuating piezo bimorph via an electrical circuit. • Spectral element formulation for the complete NRPB, including actuating cell. • Ultra-wide bandgap starting from very low frequency. [ABSTRACT FROM AUTHOR]

In this study, a magneto-mechano-electric (MME) composite cantilever made of a piezoelectric bimorph and magnets for low-frequency magnetoelectric (ME) coupling was analyzed theoretically and its MME coupling equivalent circuit was developed. Based on equivalent circuit analyses, the dependences of the ME performances, i.e., the ME voltage and charge coefficients, upon the material constants and geometrical parameters of the MME composite cantilever are numerically evaluated. The obtained ME equivalent circuit model provides a theoretical basis to understand and improve the performance of the MME composite cantilever for low-frequency ME coupling. [ABSTRACT FROM AUTHOR]

In this study, we report an enhanced electrical manipulation of magnetic susceptibility in ferromagnetic amorphous alloy ribbon using a piezoelectric bimorph actuator. Theoretically, the strain produced by the piezoelectric bimorph and then coupled into the amorphous alloy ribbon is larger than that of a single piezoelectric plate under an identical applied electric field, thus resulting in a stronger magnetoelectric (ME) coupling for electrically manipulating magnetic susceptibility. Our experimental results have shown that the initial susceptibility tunability of the amorphous alloy ribbon upon the tuning electric field applied on the piezoelectric bimorph ranging from 0 kV/cm to 5 kV/cm can reach up to 750% at low-frequency of 1 kHz and maintain 80% at 1 MHz. This study expands the structure design of ME smart devices, especially the electrically controllable magnetic devices. [ABSTRACT FROM AUTHOR]

Piezoelectric bimorphs have a promising application in morphing micro air vehicles; however, increasing the actuation displacement is a difficult point. Axial compression can be used to increase the deformation of the piezoelectric bimorph. Compared with piezoelectric ceramics, macro fiber composites offer higher flexibility. In this article, a large displacement actuator of axial-compressed macro fiber composite bimorph is proposed. A multi-layer parallel scheme of macro fiber composite bimorphs is presented to increase the output torque of piezoelectric bimorph within a limited space. The actuation performance of the axial-compressed macro fiber composite bimorph and its multi-layer parallel scheme are verified through quasi-static experiment and displacement tracking control test. The experimental results show that the end-free rotations of both the axial-compressed macro fiber composite bimorph and its multi-layer scheme achieve ±8.1°, which is 60% higher than that of a piezoelectric ceramics bimorph with the same length. The blocking torque of the single-layer macro fiber composite bimorph is 0.028 Nm. The proposed parallel bimorphs method can magnify output torques. In addition, the axial-compressed macro fiber composite bimorph can accurately track any displacement signals in the range of its actuation. It is a continuous and controllable piezoelectric bimorph with large displacement. [ABSTRACT FROM AUTHOR]

This paper presents complete nonlinear electromechanical models for energy harvesting devices consisting of multiple piezoelectric bimorphs (PBs) connected in parallel and series, for the first time. The proposed model is verified against available experimental results for a specific case. The piezoelectric and beam constitutive equations and different circuit equations are utilized to derive the complete nonlinear models for series and parallel connections of the PBs as well as those of piezoelectric layers in each bimorph, i.e., four nonlinear models in total. A multi-modal Galerkin approach is used to discretize these nonlinear electromechanical models. The resultant high-dimensional set of equations is solved utilizing a highly optimized and efficient numerical continuation code. Examining the system behavior shows that the optimum load resistance for an energy harvester array of 4 PBs connected in parallel is almost 4% of that for the case with PBs connected in series. It is shown an energy harvesting array of 8 PBs could reach a bandwidth of 14 Hz in low frequency range, i.e., 20-34 Hz. Compared with an energy harvester with 1 PB, it is shown that the bandwidth can be increased by more than 300% using 4 PBs and by more than 500% using 8 PBs. Additionally, the drawbacks of a multi-PB energy harvesting device are identified and design enhancements are proposed to improve the efficiency of the device. [ABSTRACT FROM AUTHOR]

An improved nonoptical shear force detection system based on a rectangular bimorph cantilever incorporating the force feedback technique has been developed for tip-sample distance regulation in shear force microscopy. The force feedback amplifier consisting of a phase shifter and a linear amplifier is adjusted in such a way that the motion of the cantilever is mechanically amplified, resulting in a great enhancement of quality factor Q. Driving a fiber attached bimorph cantilever at its first harmonic resonance, with a phase shift ψ = π/2 and an appropriate amplifier gain, allows one to obtain a Q factor greater than 10³ in air, which corresponds to a Q enhancement of more than 1 order of magnitude. The effect of Q enhancement leads to an increase in the signal to noise ratio and thus the force detection sensitivity of the system. Typically, the minimum interaction force that can be sensed by the system is about 2 pN/√Hz. Topographic images of a human aorta tissue section in its natural state, taken with the described shear force detection system, show that it is very sensitive, reliable, and particularly suitable for biological applications. [ABSTRACT FROM AUTHOR]

Presents information on a study which analyzed the sensing effect of cantilever mounted piezoelectric bimorph unimorph and triple layer benders subjected to external mechanical excitations. Sensor performance analysis of cantilever bimorph and unimorph benders; Sensor performance analysis of cantilever triple layer benders.

The possibility of controlling the curvature of the profiles of the surface of X-ray optical elements using single-crystal SiO2(011) plates of rectangular and trapezoidal shapes was studied. In bending regulators (BRs) of various forms, the active element was a piezoelectric bimorph glued to a single-crystal plate. Experimental and calculated data of changes in the profile and radius of curvature of the surface of the used plate are given. The influence of the forms of the components of the bending regulator is shown on the initial profile and surface curvature of X-ray optical elements. [ABSTRACT FROM AUTHOR]

Thermally responsive liquid crystal elastomers (LCEs) hold great promise in applications of soft robots and actuators because of the induced size and shape change with temperature. Experiments have successfully demonstrated that the LCE based bimorphs can be effective soft robots once integrated with soft sensors and thermal actuators. Here, we present an analytical transient thermo-mechanical model for a bimorph structure based soft robot, which consists of a strip of LCE and a thermal inert polymer actuated by an ultrathin stretchable open-mesh shaped heater to mimic the unique locomotion behaviors of an inchworm. The coupled mechanical and thermal analysis based on the thermo-mechanical theory is carried out to underpin the transient bending behavior, and a systematic understanding is therefore achieved. The key analytical results reveal that the thickness and the modulus ratio of the LCE and the inert polymer layer dominate the transient bending deformation. The analytical results will not only render fundamental understanding of the actuation of bimorph structures, but also facilitate the rational design of soft robotics. [ABSTRACT FROM AUTHOR]

• Deriving the constituent equations of PLZT micro-unimorph/bimorph. • Considering the coupled fields and size effect simultaneously. • Discussing the size effects of PLZT micro-unimorph/bimorph. The constituent equations of both 0–1 and 0–3 polarized PbLaZrTi (PLZT) micro-cantilevers in the form of unimorphs and/or bimorphs are developed. These formulations are based on the modified couple stress theory (MCST), the laminated beam theory, and/or the Euler-Bernoulli beam theory. The thermo-electro-light-mechanical coupled fields and size effect were considered simultaneously in these equations. The present models can capture the size effect in virtue of a material length scale parameter (MLSP). The size-dependent tip deflection, equivalent bending moment and blocking force are discussed. Different materials and thicknesses of the elastic layer are considered in presented models. Furthermore, the present models can be reduced to the classical 0–1/0–3 polarized unimorph/bimorph. [ABSTRACT FROM AUTHOR]

Featured Application: This investigation is to establish the model of solid–liquid coupled vibration for piezoelectric material. The experimental measurements and finite element computation results are in good agreement for both the anti-phase and in-phase vibrations coupled with various fluids. The outcome could be featured in pumping-element application that is operated efficiently in resonance. This paper describes the vibration characteristics of a dual-bimorph piezoelectric pumping element under fluid–structure coupling. Unlike the single bimorph used in most previous studies, the proposed device comprises two piezoelectric bimorphs within an acrylic housing. Amplitude-fluctuation electronic speckle pattern interferometry (AF-ESPI) was used to examine the visible displacement fringes in order to elucidate the anti-phase as well as in-phase motions associated with vibration. Analysis was also conducted using impedance analysis and laser Doppler vibrometer (LDV) based on the measurement of point-wise displacement. The experimental results of resonant frequencies and the corresponding mode shapes are in good agreement with those obtained using finite element analysis. The gain of flow rate obtained by the anti-phase motion of the dual-bimorph pumping element is larger than both those obtained by in-phase motion and the single bimorph pumping element. This work greatly enhances our understanding of the vibration characteristics of piezoelectric pumping elements with two bimorphs, and provides a valuable reference for the further development of bionic pump designs. [ABSTRACT FROM AUTHOR]

The analytical model of an axially precompressed cantilever bimorph is established using the Hamilton's principle in this study, and the static characteristics are obtained. The dynamic equations of the cantilever bimorph in generalized coordinates are established using a numerical method, and the dynamic characteristics are analyzed. Finally, simulations are performed and experiments are conducted to verify the validity of the theory. The results show that increase of axial force has significant amplification effects on the steady-state response amplitude of the displacement, and it reduces the resonance frequency. The response time is still in the millisecond range under a large axial force, which indicates that the bimorph has excellent dynamic characteristics as an actuator. [ABSTRACT FROM AUTHOR]

Swimmers at liquid/air interfaces have drawn enormous attention because of their potential applications. Described herein is one novel light‐driven swimmer based on a bimorph composite structure of a photoresponsive liquid‐crystalline polymer network and a commercially available polyimide (Kapton). The motion of the swimmer can be controlled by photoirradiation. The bilayer‐structured film shows quickly photoinduced bending towards the Kapton side upon exposure to UV light, and recovers immediately after removal of light. When placed on a liquid surface, the swimmer propels itself continually though rhythmic beating the liquid like a dolphin moving forward with its tail fin. Besides, light‐powered rotation of the swimmer is successfully achieved by simply changing the length‐width ratio and the irradiation site, mimicking the function of a dolphin's pectoral fin. Combining the forward movement and rotation motion together, on‐demand directional control of the photo‐driven swimmer can be readily obtained at room temperature, showing promise for miniaturized units for transportation. [ABSTRACT FROM AUTHOR]

Here, we discuss a novel, mixed mode 3D XYZ scanner built within a single foundry process. The device has a large range of motion in X, Y, and Z ($14.1~\mu \text{m}$ in X and Y and $97.9~\mu \text{m}$ in Z) and can also rotate about two axes (7.4°), making it a 5 degree of freedom scanner. Vertical actuation can be accomplished with both thermal actuators, which have a larger range of motion, and capacitive actuators, which are faster, responding fully up to 3.2 kHz. Although useful for many applications, including scanning probe microscopy, micrometer scale optical microscopy, and manipulation of biological objects, the device was designed to be a 3D scanner for spray-painting atoms upon a surface with nanoscale precision and resolution for nanofabrication. Demonstrating the ability to combine the device with other complicated MEMS systems, it is integrated with an XY scanner designed to serve as a shutter of atomic flux. The full system has 7 degrees of freedom and 12 actuation motors, and because it is built in a low cost commercial foundry with a robust and stable process, it is easy and inexpensive to fabricate multiple copies or integrate into other complicated systems, making a system of systems. [2018-0213] [ABSTRACT FROM AUTHOR]

Recently, the dynamic performance of piezo-electric deformable "bimorph" mirrors for synchrotron radiation and X-ray free electron laser sources has been characterized and significantly improved. This innovation enables high intensity X-ray beams to be rapidly focused or defocused to either match to the size of the sample under test or to select different sized regions of interest in larger samples. In this paper, we extend these results by monitoring a bimorph mirror using a combination of ex situ metrology instruments. Comparison between results from the Diamond-NOM (Nanometre Optical Metrology) slope profiler, a Fizeau interferometer, and Zygo ZPSTM distance measuring probes shows that bimorph X-ray mirrors can reliably and accurately be driven at 1 Hz using advanced features recently added to the high voltage (HV), bipolar "HV-Adaptos" power supply from CAEN. [ABSTRACT FROM AUTHOR]

PZT (lead zirconate titanate)-glued bimorph deformable mirrors are widely used in hard X-ray regimes; however, they have not yet been used in soft X-ray regimes because they are less compatible for usage under high vacuum. In this study, we developed a glue-free bimorph deformable mirror, in which silver nano-particles were employed to bond PZT actuators to mirror substrates. Under an appropriate bonding condition, the bonding layer was confirmed to be uniform and the mirror's bending characteristics were demonstrated to be sufficiently stable; its gas emission rate was also shown to be acceptable. Piezo responses before and after additional heating at 200 °C showed the thermal stability of its bonding and bending properties. [ABSTRACT FROM AUTHOR]

Piezoelectric bimorph deformable mirrors ('bimorphs') are routinely used on many synchrotron and free‐electron laser beamlines to provide active variation in the size and shape of the X‐ray beam. However, the time‐domain potential of such optics has never been fully exploited. For the first time, the fast dynamic bending response of bimorphs is investigated here using Fizeau interferometry. Automated scripts for acquisition and analysis were developed to collect Fizeau data at a rate of 0.1 Hz to record dynamic changes in the optical surface as voltages were applied to the electrodes of the piezoelectric actuators. It is demonstrated that residual drift in the tangential radius of curvature of a bimorph can be significantly reduced using enhanced opto‐mechanical holders and a fast programmable high‐voltage power supply. Further improvements are achieved by applying small opposing voltages to compensate for piezoelectric creep. The present study shows that bimorphs can truly be used as high‐speed adaptive optics for the X‐ray domain, even without closed‐loop feedback correction. This opens the possibility for relatively simple real‐time tuning of the profile of X‐ray bimorphs. Part II of this study [Alcock, Nistea, Signorato, Owen, Axford, Sutter, Foster & Sawhney (2019), J. Synchrotron Rad.26, 45–51] builds upon these results and demonstrates how bimorphs can rapidly provide customisable sizes and shapes of synchrotron X‐ray beams, specifically tailored to suit the experimental samples being investigated. The time‐domain bending behaviour of piezoelectric bimorph deformable X‐ray mirrors for use at synchrotron and X‐ray free‐electron laser sources is investigated for the first time using high‐speed Fizeau interferometry. It is demonstrated that several hardware and software innovations enable the optical surface of such mirrors to be rapidly tuned and stabilized on the nanometre scale within only a few seconds. [ABSTRACT FROM AUTHOR]

This paper proposes a bimorph piezoelectric vibration energy harvester (PVEH) with a flexible 3D meshed-core elastic layer for improving the output power while lowering the resonance frequency. Owing to the high void ratio of the 3D meshed-core structure, the bending stiffness of the cantilever can be lowered. Thus, the deflection of the harvester and the strain in the piezoelectric layer increase. According to vibration tests, the resonance frequency is 15.8% lower and the output power is 68% higher than in the conventional solid-core PVEH. Compared to the solid-core PVEH, the proposed meshed-core PVEH (10 mm × 20 mm × 280 μm) has 1.3 times larger tip deflection and the maximum output power is 24.6 μW under resonance condition at 18.7 Hz and 0.2G acceleration. Hence it can be used as a power supply for low-power-consumption sensor nodes in wireless sensor networks. [ABSTRACT FROM AUTHOR]

We establish and analyze an analytical framework by accounting for both the piezoelectric and flexoelectric effects in bimorph cantilevers. The focus is placed on the development of governing electroelastodynamic piezoelectric–flexoelectric equations for the problems of resonant energy harvesting, sensing, and actuation. The coupled governing equations are analyzed to obtain closed-form frequency response expressions via modal analysis. The combined piezoelectric–flexoelectric coupling coefficient expression is identified and its size dependence is explored. Specifically, a typical atomistic value of the flexoelectric constant for barium titanate is employed in the model simulations along with its piezoelectric constant from the existing literature. It is shown that the effective electromechanical coupling of a piezoelectric material, such as barium titanate, is significantly enhanced for thickness levels below 100 nm. The electromechanical coupling coefficient of a barium titanate bimorph cantilever increases from the bulk piezoelectric value of 0.065 to the combined piezoelectric–flexoelectric value exceeding 0.3 toward nanometer thickness level. Electromechanical frequency response functions for resonant power generation and dynamic actuation also capture the size-dependent enhancement of the electromechanical coupling. The analytical framework given here can be used for parameter identification and design of nanoscale cantilevers that can be used as energy harvesters, sensors, and actuators. [ABSTRACT FROM AUTHOR]

A typical linear piezoelectric energy harvester (PEH) is represented by a unimorph or bimorph cantilever beam. To improve the efficiency of linear PEHs, classical strategies involve the increase of the beam length, tapering or adding additional cantilever beams to the free end. In this work we discuss the design of novel type of composite linear multi-layer piezoelectric energy harvester (MPEH). MPEHs here consist of carbon fibre laminates used as conducting layers, and glass fibre laminas as insulating components. We develop first a electromechanical model of the MPEH with parallel connection of PZT layers based on Euler-Bernoulli beam theory. The voltage and beam motion equations are obtained for harmonic excitations at arbitrary frequencies, and the coupling effect can be obtained from the response of the system. A direct comparison between MPEH and PEH configurations is performed both from the simulation (analytical and numerical) and experimental point of views. The experiments agree well with the model developed, and show that a MPEH configuration with the same flexural stiffness of a PEH can generate up to 1.98–2.5 times higher voltage output than a typical piezoelectric energy harvester with the same load resistance. [ABSTRACT FROM AUTHOR]

In this paper, we show that torsional as well as flexion modes can be excited rather naturally in a magnetoelastic bimorph. This behavior is in contrast with that of usual piezoelectric bimorphs in which only flexion modes can be excited. We describe experimental results on the torsional resonances of bimorphs composed of a glass substrate and a highly magnetostrictive thin film of (TbDy)(FeCo)[sub 2] and show how basic linear piezomagnetic constants may be extracted from the resonance data. Finally, we discuss some possible applications of torsional resonance in magnetoelastic bimorphs. [ABSTRACT FROM AUTHOR]

Biomorphs are graphic objects with very interesting shapes resembling unicellular and microbial organisms such as bacteria. They have applications in different fields like medical science, art, painting, engineering and the textile industry. In this paper, we present for the first time escape criterion results for general complex polynomials containing quadratic, cubic and higher order polynomials. We do so by using a more general iteration method also used for the first time in this field. This also generalizes some previous results. Then, biomorphs are generated using an algorithm whose pseudocode is included. A visualization of the biomorphs for certain polynomials is presented and their graphical behaviour with respect to variation of parameters is examined.

The mechanical quality factor and the resonant magnetoelectric (ME) response of multi-push-pull mode Metglas/interdigitated (ID)-electrode/Pb(Zr,Ti)O3 (PZT) ME resonators have been studied as a function of ID-electrode geometry for both sandwich and bimorph configurations. The results show that the mechanical quality factor of the PZT core composite and the effective mechanical quality factor of the ME resonator are increased with increasing ID-electrode spacing. The sandwich resonator was found to exhibit a higher effective mechanical quality factor than the bimorph one. [ABSTRACT FROM AUTHOR]

Studies in recent years have focused mainly on strain mediated magnetoelectric (ME) effects in magnetostrictive-piezoelectric composites. This report is on resonance ME effects in a piezoelectric bimorph. The effect arises due to combination of piezoelectricity and the Ampere force on the sample that carries an ac electric current and placed in a bias magnetic field. The ME coefficient is as high as 16.5 V/(A kOe) at 153 Hz due to bending oscillations. Estimated ME coefficients are in agreement with the data. [ABSTRACT FROM AUTHOR]

This article illustrates performance improvement of a piezo-bimorph actuator by tailoring its geometry. We have analytically presented that a piezo-bimorph actuator with a tapered surface provides superior performance for out-of-plane bending compared to a rectangular surface while having equal mass and equal primary capacitance. Equal capacitance ensures equal input electrical energy and bandwidth for both the cases below its first resonant frequency. We have analytically derived performance measuring attributes of such an actuator considering high electric field, and shown the performance improvement quantitatively. We have also presented finite element solutions to compare with the analytical solutions. Some results are validated with the earlier published experimental results. [ABSTRACT FROM AUTHOR]

Cu-Al-Ni and Cu-Al-Ni-Mn shape memory alloys are deposited on Kapton polyimide sheets by a physical evaporation technique. Detailed investigations on the morphological, structural and thermal behaviour of the ternary and quaternary alloys are conducted. The developed samples exhibit an increase in martensite structures and decrease in transformation temperatures after Mn additions. Furthermore, the suppression of Cu 3 Al precipitates was evident from XRD analysis. The thermomechanical behaviour was analysed by actuating the bimorphs through Joule heating under varying mechanical loads. Fatigue analysis of the bimorphs reveals a superior performance for Cu-Al-Ni-Mn, exhibiting less than 30% loss in displacement after 15,000 cycles. [ABSTRACT FROM AUTHOR]

This article presents an electromechanical analysis for a piezoelectric bimorph actuator with a flexible extension, which is used to increase the tip deflection. The performance measuring attributes of such an actuator are derived, and a genetic algorithm is used for multi-objective optimization. The analysis reveals that for a thick flexible extension, the length of the extension provides Pareto optimal solutions for multi-objective optimization. The analysis also shows that as the thickness of the flexible extension decreases, the Pareto optimal solutions converge to a single solution for multi-objective optimization. We have considered nonlinear deflection behavior of piezoelectric materials at high electric fields, and series and parallel electrical connections in the analysis. [ABSTRACT FROM AUTHOR]

Summary: Micro/nanomanipulation is a rapidly growing technology and holds promising applications in various fields, including photonic/electronic devices, chemical/biosensors etc. In this work, we present that shear force microscopy (ShFM) can be exploited to manipulate metallic nanosheets besides imaging. The manipulation is realized via controlling the shear force sensor probe position and shear force magnitude based on our homemade ShFM system under an optical microscopy for in situ observation. The main feature of the ShFM system is usage of a piezoelectric bimorph sensor, which has the ability of self‐excitation and detection. Moreover, the shear force magnitude as a function of the spring constant of the sensor and setpoint is obtained, which indicates that operation modes can be switched between imaging and manipulation through designing the spring constant before experiment and changing the setpoint during manipulation process, respectively. We believe that this alternative manipulation technique could be used to assemble other nanostructures with different shapes, sizes and compositions for new properties and wider applications. [ABSTRACT FROM AUTHOR]

In this research four piezoelectric bimorph type cantilevers for energy harvesting were manufactured, measured and analyzed to study the effects of substrate layer thickness on energy harvesting efficiency and durability under different accelerations. The cantilevers had the same dimensions of the piezoelectric ceramic components, but had different thicknesses of the steel substrate (no steel, 30 µm, 50 µm and 75 µm). The cantilevers were tuned to the same resonance frequency with different sizes of tip mass (2.13 g, 3.84 g, 4.17 g and 5.08 g). The energy harvester voltage outputs were then measured across an electrical load near to the resonance frequency (∼40 Hz) with sinusoidal vibrations under different accelerations. The stress exhibited by the four cantilevers was compared and analyzed and their durability was tested with accelerations up to 2.5 g-forces. [ABSTRACT FROM AUTHOR]

A typical vibration harvester is tuned to operate at resonance in order to maximize the power output. There are many design parameter sets for tuning the harvester to a specific frequency, even for simple geometries. This work studies the impact of the geometrical parameters on the harvested power while keeping the resonance frequency constant in order to find the combination of the parameters that optimizes the power under a predefined volume. A bimorph piezoelectric cantilever is considered for the study. It consists of two piezoelectric layers and a middle non-piezoelectric layer and holds a tip mass. A theoretical model was derived to obtain the system parameters and the power as functions of the design parameters. Formulas for the optimal load resistance that provide maximum power capability at resonance and anti-resonance frequency were derived. The influence of the width on the power is studied, considering a constant mass ratio (between the tip mass and the mass of the beam). This keeps the resonance frequency constant while changing the width. The influence of the ratio between the thickness of the middle layer and that of the piezoelectric layer is also studied. It is assumed that the total thickness of the cantilever is constant and the middle layer has the same mechanical properties (elasticity and density) as the piezoelectric layer. This keeps the resonance frequency constant while changing the ratio between the thicknesses. Finally, the influence of increasing the free length as well as of increasing the mass ratio on the power is investigated. This is done by first, increasing each of them individually and secondly, by increasing each of them simultaneously while increasing the total thickness under the condition of maintaining a constant resonance frequency. Based on the analysis of these influences, recommendations as to how to maximize the geometrical parameters within the available volume and mass are presented. [ABSTRACT FROM AUTHOR]

Optimal configuration of anisotropic piezocomposite actuators is investigated for vibration control of flexible structures. Actuation effects of the actuators in unimorph and antisymmetric angle-ply bimorph configurations are analyzed. Dynamic equations of the piezo-actuated plate are established using finite element method. The locations and lead zirconate titanate fiber orientations of actuators are optimized simultaneously to improve vibration control performance of a plate. The optimization criterion is presented based on controllability Gramian matrix of the system. The properties of macro-fiber composite are used in the simulations of the actuators. The optimal unimorph and bimorph configurations of actuators are presented for three cases: bending control, twisting control, and coupled bending-twisting control. The results indicate that both optimal locations and fiber orientations are different for bending control and twisting control. A trade-off between control authority for bending and torsional modes can be found in coupled bending-twisting control. The actuators should be placed in the regions of high average strain of the interested modes with appropriate fiber orientations. Special piezocomposite actuators with optimal fiber orientations can be used to achieve improved coupled bending-twisting vibration control performance. [ABSTRACT FROM AUTHOR]

A new analytical model is proposed for the estimation of interlaminar shear stress in adhesively bonded metal laminates consisting of an arbitrary number of layers. The interface shear stress in the laminates is related to the difference in average axial strain and elongation between adjoining layers through a newly proposed interlaminar shear stress function (ILSSF). The parameters of the ILSSF are determined from finite element simulations using a data fitting procedure. The accuracy of the model is investigated by comparing experimental measurements of average elongation in three-layer aluminum laminates to values obtained using the model. Good agreement with the experimental results is achieved for several types of adhesives and for different ratios of adhesive-to-layer thicknesses. The influence of Young's modulus of the adhesive on the efficiency of load transfer in three-layer laminates is investigated. [ABSTRACT FROM AUTHOR]

Harvesting the energy from base vibration through a Piezo-electric Transducer (PZT) is an adaptable and an emerging technique in recent years. The power output of piezoelectric energy harvester can be improved by an appropriate configuration of its geometry and positioning of additional mass. This paper presents a numerical study on a cantilever energy harvester to quantify the energy harvested from vibration having a single frequency harmonic excitation and discusses the effect of base acceleration on the energy output for different beam widths and proof masses. It focusses on the numerical simulation procedure necessary to develop a deeper understanding on the performance of the harvester. The methodology adopted to finalise the geometry and the proof mass is explained. The configuration of the cantilever energy harvesting structure includes structural steel cantilever beam sandwiched between two PZT layers. The beam is subjected to harmonic excitation. The results suggest that the bimorph configuration produces more energy output when the ratio of length to width of beam is more with large proof mass, provided the induced stress in the piezoelectric material is within the permissible limits. The studies demonstrated that the finalised harvester can deliver a maximum of 880mW of power to a matched resistive load of 12k£2, when exposed to a base acceleration of 30g at the resonant frequency of 77.5Hz. [ABSTRACT FROM AUTHOR]

The problem of the forced vibrations and dissipative heating of piezoelectric rectangular plates with open electrodes and hinged ends under harmonic surface uniform pressure is stated. The electromechanical problem is reduced to an infinite system of algebraic equations. The exact analytical solution of this system is found and the exact analytical solution of the energy equation is obtained for vibrations at the first resonant frequency. A formula for the critical pressure reaching which the plate no longer performs its function due to loss of the piezoeffect is derived. [ABSTRACT FROM AUTHOR]

In this article, a numerical investigation is performed for ambient acoustic energy harvesting at a low-frequency acoustic signal. A model of a quarter-wavelength resonator with a rectangular cross section is constructed, and piezoelectric-laminated bimorph plates are placed inside the system. Finite element modeling is implemented to numerically formulate the piezoelectric energy harvester. With the application of acoustic pressure at the open end of the resonator, amplified acoustic pressure inside the tube vibrates the piezolaminated bimorphs inside the tube, thus generating electric potential on the piezoelectric layers. To generate higher voltage and power in the acoustic harvester, multiple piezolaminated plates are positioned inside the resonator. The lead-free piezoelectric material KNaLi (NbTaSb)O (KNLNTS) is laminated on the host structure as a layer of piezoelectric material for the acoustic energy harvester. With the application of an acoustic sound pressure of 1 dB at the opening of the tube, a maximum output voltage of 16.3 V is measured at the first natural frequency, while the maximum power calculated is 0.033 mW. Maximum voltage is obtained when five piezoelectric bimorphs are place inside the resonator. At the second natural frequency, the maximum voltage measured is 8.40 V, obtained when eight piezoelectric bimorphs are placed inside the resonator, and the maximum power calculated is 0.020 mW. [ABSTRACT FROM AUTHOR]