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The development of micro-robots based on bionic motion has garnered increasing attention with the advancement of bionic technology. These micro-robots can be employed in various tasks, such as military applications, disaster search and rescue, in vivo drug delivery, minimally invasive surgery, and tumor treatment. Robot joint motion is commonly achieved through actuators, which encompass motor, hydraulic, or pneumatic components that often carry excessive weight. To achieve the goal of miniaturizing robotic mechanisms, innovative actuators need to be developed. This study focuses on designing a four-limbed micro-robot that utilizes piezoelectric actuators. Automatic Dynamic Analysis of the Mechanical System is employed to investigate the kinematic aspects of the micro-robot’s motion, and finite element analysis is also used to obtain the resonant characteristics of the limbs actuated by piezoelectric bimorphs. The results indicate that the gait pattern of a piezoelectric robot changes according to the walking strategy and the robot dimension. The forward travel speed varies depending on the gait pattern, and adjustments in gait design can reduce the up/down oscillation and right/left offset. The robot’s travel speed increases with both trunk and limb length, although longer thigh and leg lengths might lead to greater offset and vertical oscillation. The resonant frequency and mode shapes change with the limb structure and affect the limb motion style. By adjusting the driving frequency of the bimorph actuators, the gait pattern can be manipulated. The information presented in this study contributes to a deeper understanding of micro-robot design. [ABSTRACT FROM AUTHOR]

Helium is integral in several industries, including nuclear waste management and semiconductors. Thus, developing a sensing method for detecting helium is essential to ensure the proper operation of such facilities. Several approaches can be used for helium detection, including based on the high thermal conductivity of helium, which is several times higher than air. This work utilizes the high thermal conductivity of helium to design and analyze a bimorph MEMS sensor for helium sensing applications. COMSOL Multiphysics software (version 6.2) is used to carry out this investigation. The sensor is constructed from poly-silicon and SiO2 materials with a trenched cantilever beam configuration. The sensor is electrically heated, and its morphed displacement depends on the surrounding gas's composition, which decreases in the presence of helium. Several factors were investigated to probe their effect on the sensor's sensitivity to helium, including the thickness of the poly-silicon layer, the configuration of the trench, and the thickness and location of SiO2 layer. The simulations showed that the best performance, up to 2 ppm helium detection level, can be achieved with thinner beams and medium trench lengths. [ABSTRACT FROM AUTHOR]

This paper reports two piezoelectric materials of lead zirconium titanate (PZT) and aluminum nitride (AlN) used to simulate microelectromechanical system (MEMS) speakers, which inevitably suffered deflections as induced via the stress gradient during the fabrication processes. The main issue is the vibrated deflection from the diaphragm that influences the sound pressure level (SPL) of MEMS speakers. To comprehend the correlation between the geometry of the diaphragm and vibration deflection in cantilevers with the same condition of activated voltage and frequency, we compared four types of geometries of cantilevers including square, hexagon, octagon, and decagon in triangular membranes with unimorphic and bimorphic composition by utilizing finite element method (FEM) for physical and structural analyses. The size of different geometric speakers did not exceed 10.39 mm2; the simulation results reveal that under the same condition of activated voltage, the associated acoustic performance, such as SPL for AlN, is in good comparison with the simulation results of the published literature. These FEM simulation results of different types of cantilever geometries provide a methodology design toward practical applications of piezoelectric MEMS speakers in the acoustic performance of stress gradient-induced deflection in triangular bimorphic membranes. [ABSTRACT FROM AUTHOR]

In this paper, we consider transverse steady oscillations of a piezoactive bimorph in the formulation of a plane deformation. The problem is solved within the framework of linear thermoelectroelasticity, while the temperature problem is solved separately and the temperature distribution is taken into account in the constitutive relations of electroelasticity. On the basis the Kirchhoff–Love type hypothesis for mechanical quantities and a symmetric quadratic distribution of the electric potential, an approximate theory for calculating bimorph vibrations is constructed. Numerical experiments have been carried out for various cases of pinning and excitation of vibrations. The results of these experiments were compared with calculations made using the finite element method in the COMSOL package, which showed the adequacy of the constructed theory in the low-frequency region. [ABSTRACT FROM AUTHOR]

We study the bending of a two-layer piezoelectric semiconductor plate (bimorph). The macroscopic theory of piezoelectric semiconductors is employed. A set of two-dimensional plate equations is derived from the three-dimensional equations. The plate equations exhibit direct couplings among bending, electric polarization along the plate thickness, and mobile charges. In the case of pure bending, a combination of physical and geometric parameters is identified which characterizes the strength of the interaction between the mechanical load and the distribution of mobile charges. In the bending of a rectangular plate under a distributed transverse mechanical load, it is shown that mobile charge distributions and potential barriers/wells develop in the plate. When the mechanical load is local and self-balanced, the induced carrier distributions and potential barriers/wells are also localized near the loading area. The results are fundamentally useful for mechanically manipulating mobile charges in piezoelectric semiconductor devices. [ABSTRACT FROM AUTHOR]

Cardiac auscultation is an orthodox method to prevent and diagnose cardiovascular diseases. Traditional stethoscopes cannot offer a highly reliable diagnosis, and electronic stethoscopes suffer from low signal-to-noise ratio (SNR) and high cost. This paper reports an electronic stethoscope based on piezoelectric bimorph MEMS transducers for cardiac sound monitoring. The stethoscope prototype, measuring 37 $\times 28\times12$ mm3, contains a preamplifier, holders and polydimethylsiloxane (PDMS) packaging. The transducer is designed using a lumped element model, fabricated by MEMS process, packaged, and assembled for final use. A triangular cantilever is chosen as a basic element for the transducer, with analytical analysis showing high sensitivity per unit area as a figure of merit (FoM). Performance parameters such as sensitivity and noise are experimentally characterized and consistent with simulation results. Owing to the outstanding receiving performance of the aluminum nitride (AlN) material and bimorph triangular cantilever structure of the transducer, compared with the commercial electronic stethoscopes, the proposed stethoscope demonstrates real-time phonocardiogram (PCG) with higher SNR. With its small size, high performance and low cost, the stethoscope is developed for portable and wearable cardiac sound monitoring. [2022-0007] [ABSTRACT FROM AUTHOR]

Piezoelectric harvesters use the actuation potential of the piezoelectric material to transform mechanical and vibrational energies into electrical power, scavenging energy from their environment. Few research has been focused on the development and understanding of the piezoelectric harvesters from the material themselves and the real piezoelectric and mechanical properties of the harvester. In the present work, the authors propose a behavior real model based on the experimentally measured electromechanical parameters of a homemade PZT bimorph harvester with the aim to predict its Vrms output. To adjust the harvester behavior, an iterative customized algorithm has been developed in order to adapt the electromechanical coupling coefficient, finding the relationship between the harvester actuator and generator behavior. It has been demonstrated that the harvester adapts its elongation and its piezoelectric coefficients combining the effect of the applied mechanical strain and the electrical behavior as a more realistic behavior due to the electromechanical nature of the material. The complex rms voltage output of the homemade bimorph harvester in the frequency domain has been successfully reproduced by the proposed model. The Behavior Real Model, BRM, developed could become a powerful tool for the design and manufacturing of a piezoelectric harvester based on its customized dimensions, configuration, and the piezoelectric properties of the smart materials. [ABSTRACT FROM AUTHOR]

This paper reports a bimorph pinned piezoelectric micromachined ultrasonic transducer (PMUT) for enhanced sound pressure output and electromechanical coupling factor for space imaging applications. An equivalent circuit model has been built to analyze the dynamic behavior of PMUTs and prototype devices have been designed, fabricated. Experimental results show a 58% measured increase in the electromechanical coupling factor and pulse-echo measurements show a 4-meter traveling distance in air under a 133 kHz driving frequency. As a demonstration example, a relatively long-distance (> 1.5 meters) ultrasound imaging test in air is conducted using a 4 × 4 bimorph, pinned dual-electrode PMUTs array based on the transmission beamforming scheme. As such, this work enhances and extends the PMUT performances and capabilities for potential broad applications. [2021-0102] [ABSTRACT FROM AUTHOR]

Commonly, linear constitutive equations have been utilized for describing the electromechanical behavior of piezoelectric actuators. These equations are valid for low excitation amplitudes and small strains. In high strain dynamics, nonlinear constitutive equations should be applied which include the material nonlinearity by expressing the stress as a function of higher orders of strain. In this article, nonlinear dynamic modeling of bimorph transverse actuators around the natural frequency has been investigated. The nonlinear equation is solved with perturbation methods and the model parameters are identified with experiments. Experimental results illustrate the improvement of nonlinear dynamic modeling compared with conventional linear models. [ABSTRACT FROM AUTHOR]

In this paper, the stress behaviour and power generation of cymbal bimorph transducer of different piezoelectric ceramics are studied. Comparison of stress, deformation and power is done between different materials cymbal bimorph transducer. The cymbal bimorph design is made on Solidworks, and simulation is carried out on ANSYS 18.0. In this design, the substrate thickness is varied. Its both end surface is bonded to the piezoelectric layers of 0.50 mm thickness and further piezoelectric layers bonded to endcaps. A 100 N of the load is applied at the apex of end caps. The lead-free ceramics and lead-based ceramic are used as a piezoelectric material in the design. The stress and power are calculated for different values of thickness of the substrate, and comparison is made among them. After having a comparison it is found that both types of ceramics can be used, but there are some conditions which prioritise lead-free ceramic over lead-based ceramic. [ABSTRACT FROM AUTHOR]

Piezoelectric energy harvesting (PEH) provides an essential mode for the transformation of mechanical vibration to electrical form for providing continuous power to wireless sensor nodes in today's connected world. This work describes an analytical model based on the Euler-Bernoulli model. The proposed model is in agreement with the FEM simulation model, with results differing by 6%. Variation in geometric parameter, the effect of resonant frequency, output power and stability of the design provides a constraint domain for structure optimization have been described along with the effect of damping. The designed harvester generates a power of 1.31 mW at 90 Hz resonant frequency. [ABSTRACT FROM AUTHOR]

Piezoelectric actuators are widely used in many fields such as medical instruments, optics, and aerospace due to their small size and high reliability. Piezoelectric cantilever actuators are used in different configurations such as unimorph and bimorph. In this paper, a 3-D lead zirconate titanate (PZT) bimorph was modeled in COMSOL Multiphysics software for investigation of series and parallel configuration. Theoretical analysis has been developed for the measurement of deformation of a piezoelectric cantilever in inverse piezoelectric effect. The experiment was also performed to examine the deformation of piezoelectric bimorph cantilever. It is found that under a constant applied electric field of 100 V bimorph piezoelectric actuator produces maximum deformation at 100 mm length, 30 mm width, and 20 mm thickness. It is also found that piezoelectric series benders have relatively less deformation than piezoelectric parallel benders. Experimental results show good agreement with theoretical and Numerical results. [ABSTRACT FROM AUTHOR]

• A complementary strategy can work as a universal design principle for dual-responsive actuators. • Combining moisture-active/alkane-inert GO with alkane-active/moisture-inert PDMS enables dual-responsive actuation. • GO and PDMS bimorph features fast and reversible response to both moisture and alkane. Smart actuators that enable deforming in a predictable manner under external stimuli have revealed great potential for both traditional and emerging industries. Generally, an asymmetric bilayer structure with one layer active and the other inert to a certain stimulus is essential to realize bending behavior. However, towards the development of dual- or multi-responsive actuators, it still lacks universal and effective strategies for rational design and fabrication of such devices through the simplest way. In this paper, we report a complementary strategy to produce dual-responsive bilayer actuators by combining the moisture-active/alkane-inert graphene oxide (GO) layer with the alkane-active/moisture-inert polydimethylsiloxane (PDMS) layer. The GO@PDMS bimorph actuator can switch its active and inert layers in response to moisture and alkane, respectively, realizing dual-responsive deformation under different actuations. Typical dual-responsive actuators, including a selective air valve and a grip and hook smart claw, are successfully fabricated, demonstrating the capability of effective gases and objects transmission. The complementary bimorph actuator may hold great promise for developing intelligent devices and portable delivery systems. [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]

High-precision delivery of fluids is an important tool in modern science and technology, and the demand for the precise control of insulin amount in the body of patients with diabetes is increasing. In this study, a novel stick–slip piezoelectric actuator based on a V-shaped driving mechanism is proposed to achieve a large lateral displacement. The actuator stator is fabricated using beryllium and lead zirconate titanate thick films, which form a bimorph. It is based on the stick–slip driving principle and uses the coupled motion of the proposed V-shaped stator to produce a clamping action in the stick phase and a release action in the slip phase. A theoretical structure model based on structural mechanics is proposed, and a simulation analysis is conducted to predict output performance. Experimental results indicate that the slider step displacement is 1.04 μ m under 1 Hz, 100 V p p. The slider speed increases linearly as the driving frequency and voltage increase. The step displacement also increases linearly as the driving voltage increases. A displacement difference of 0.04 μ m exists between forward and reverse motions. A sawtooth-holding wave is proposed to reduce backward displacement, achieving an increased step displacement of 32 %. [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]

Highlights • The approach uses coupled actuators to stimulate the finger in two directions. • This stimulation provides a better user experience than conventional approaches. • Each individual actuator requires only a round surface with a diameter of 2.3 mm. • The lateral actuator was described and designed with a comprehensive model. • The concept of the bimodal tactile display is validated by various experiments. Abstract In this paper, a bimodal tactile display used to stimulate the mechanoreceptors is proposed. The use of tactile displays to provide tactile sensations has become the object of increasing interest in recent years. Most of these displays have only one actuator type to generate the tactile perceptions and the spatial resolution of many displays is too rough for good tactile impression. Hence, for the proposed tactile display, two types of actuators for lateral and vertical (normal) excitation are combined. The resolution of the 4 × 4 array is 2.4 mm. Due to its design concept, the presented display is easily expanded. The normal actuator is based on the reluctance principle and the lateral actuator is based on the piezoelectric effect. This contribution focuses on the design and characterization of the piezoelectric actuator. The lateral actuator is mounted on the normal actuator. This has a significant impact on the design of the piezoelectric actuator. To describe the dynamics of this actuator, a Transfer Matrix Method (TMM) Model is created. The mechanical boundary condition at the connection to the normal actuator is included utilizing discrete elements. The model is validated by experiments. Using the model, the geometry of the actuator elements is designed. For performance tests, several experiments have been carried out. The behavior of the lateral actuator has been analyzed in the two end positions of the normal actuators for different load conditions. In terms of performance, the lateral actuators achieve sufficient deflection, even under high load conditions, using imitation human skin as the contact material and with a weight of 50 g. It is shown in a subject test that the lateral actuator works well under real conditions. A measurement of the combined movement has been performed using a Micro System Analyzer (MSA-100-3D) at different frequencies. [ABSTRACT FROM AUTHOR]

Vertical comb drives are critical for electrostatic optical switches and variable optical attenuators (VOAs), but fabricating vertical comb drives requires the formation of two levels of comb fingers and thus suffers from the difficulty of dealing with the comb-finger alignment. This paper presents a vertical comb drive design and its micro-fabrication method that can realize self-aligned two-level comb fingers. The self-aligned vertical comb fingers are enabled by a novel vertically-elevated flat-end (VEFE) bimorph structure. Both the stator and rotor fingers of the vertical comb drive are formed by the same photomask and the same silicon etching step, which automatically ensures accurate alignment of the stator and rotor fingers. The vertical separation between the stator and rotor is created by the VEFE structure. A 1mm-aperture MEMS mirror with the proposed VEFE comb drive has been fabricated using SOI wafers with buried cavities. The mirror rotates 0.94° at 8 Vdc. The resonant frequency is 1.428 kHz. The MEMS mirror has been assembled into a VOA module. Measurements show that the VOA achieved a dynamic range of 55 dB and an insertion loss of less than 0.4 dB and met the telecommunications standards on shock, vibration and long-term stability. [ABSTRACT FROM AUTHOR]

Origami-inspired fabrication presents an attractive platform for miniaturizing machines: thinner layers of folding material lead to smaller devices, provided that key functional aspects, such as conductivity, stiffness, and flexibility, are persevered. Here, we show origami fabrication at its ultimate limit by using 2D atomic membranes as a folding material. As a prototype, we bond graphene sheets to nanometer-thick layers of glass to make ultra- thin bimorph actuators that bend to micrometer radii of curvature in response to small strain differentials. These strains are two orders of magnitude lower than the fracture threshold for the device, thus maintaining conductivity across the structure. By patterning 2-µm-thick rigid panels on top of bimorphs, we localize bending to the unpatterned regions to produce folds. Although the graphene bimorphs are only nanometers thick, they can lift these panels, the weight equivalent of a 500-nm-thick silicon chip. Using panels and bimorphs, we can scale down existing origami patterns to produce a wide range of machines. These machines change shape in fractions of a second when crossing a tunable pH threshold, showing that they sense their environments, respond, and perform useful functions on time and length scales comparable with microscale biological organisms. With the incorporation of electronic, photonic, and chemical payloads, these basic elements will become a powerful platform for robotics at the micrometer scale. [ABSTRACT FROM AUTHOR]

The development of flexible film/substrate composite systems has emerged as a promising strategy to enhance the functionality of sub-micron NiTi (Nickel–Titanium) thin films. Among potential substrates, polyimide foils offer many advantages as they are lightweight, flexible, and durable. However, the properties and behavior of NiTi films deposited on polyimides remain poorly understood compared to films on traditional substrates. In this work, NiTi films were sputter-deposited simultaneously onto polyimide foils (Kapton) and Si wafers under various conditions. The films' composition, crystalline nature, and morphology were analyzed and compared. The films deposited on polyimide exhibited distinct differences in Ni content (1.0 -4.4 at.% lower), thickness, grain morphology, and crystal structure compared to those deposited on Si. The differences in properties between polyimides and Si (e.g., surface energy, thermal conductivity) induced noticeable effects on NiTi film growth and final structure. These discrepancies can lead to different optical, wetting, superelastic, and shape memory behavior, as demonstrated by the pseudo-two-way shape memory effect observed in only one of the NiTi/Kapton actuators. Our findings highlight the need for further investigations of the interactions between NiTi films and polyimide substrates, which will facilitate the development of sub-micron NiTi-based applications such as wearable electronics. [Display omitted] • Sub-micron Nickel–Titanium films were sputtered on polyimide foils and Si wafers. • NiTi films' Ni content on polymide were 1.0 - 4.4 at.% lower than on the Si wafers. • The films on polyimide were 63–123% of the thickness of films on Si. • Films on polyimide were morphologically and structurally different than films on Si. [ABSTRACT FROM AUTHOR]

Magnetoelectric (ME) interaction in magnetostrictive-piezoelectric multiferroic structures consists in inducing the electric field across the structure in an applied magnetic field and is a product property of magnetostriction and piezoelectricity in components. ME voltage coefficient that is the ratio of induced electric field to applied magnetic field is the key parameter of ME coupling strength. It has been known that the ME coupling strength is dictated by the product of the piezoelectric and piezomagnetic coefficients of initial phases. As a result, using the laminates with graded piezoelectric and piezomagnetic parameters are a new pathway to the increase in the ME coupling strength. Recently developed models predict stronger ME interactions in composites based on graded components compared to homogeneous ones. We discuss predicting the ME coupling strength for layered structures of homogeneous and compositionally graded magnetostrictive and piezoelectric components based on the graphs of ME voltage coefficients against composite parameters. For obtaining the graphs, we developed equations for ME output in applied magnetic field for possible modes of operation and layered structure configurations. In particular, our studies have been performed on low-frequency ME coupling, enhanced ME effect in electromechanical resonance (EMR) region for longitudinal and bending modes. Additionally, ME coupling at magnetic resonance in magnetostrictive component and at overlapping the EMR and magnetic resonance is investigated. We considered symmetric trilayers and asymmetric bilayers of magnetostrictive and piezoelectric components and multilayered structures based on compositionally stepped initial components. [ABSTRACT FROM AUTHOR]

Typical pneumatic actuators provide one directional linear motion, but in many applications bending motion is required. Achieving bending motion with a typical pneumatic actuator requires a complex mechanism to translate the linear motion into bending. Hence, a bending pneumatic actuator will be desirable. This paper presents a bending pneumatic actuator that can be mass-produced. This actuator was modelled by using finite element analysis over a range of parameters. Systematic experimentation was carried out to validate the FEA simulations. A pneumatic bending actuator of length 180–220 mm, inner diameter 7–11 mm, wall thickness 2–3.2 mm, is capable of generating blocking force up to 7.32 N and bending angle up to 224.3° with an input pressure of 0.675 MPa and an operating switching frequency of 20 Hz with no more than 7% radial expansion for the samples under test. The low profile, light weight, compliant nature and robustness of the actuators developed in this work lead to a large variety of potential applications. [ABSTRACT FROM AUTHOR]

A dynamic analytical model is developed to predict the performance of a triple-layer piezoelectric cantilever as actuators in relation to materials with large piezoelectric and electromechanical coupling (EMC) coefficients under axial stress and plane strain conditions. The dynamic electromechanical behavior of a symmetrical triple-layer piezoelectric cantilever (STLPC) actuator is investigated. The analytical model of STLPC based on electromechanical coupling correction coefficient (EMCC) is established in one-dimensional (1D) form and applied to 1D and 2D deformations. Furthermore, the theoretical analysis of the EMCC model is critically evaluated and compared with the simulations using a finite element method (FEM). Results show that the EMCC model can be accurately applied to analyze the actuation performance of STLPC. Analyzed results show that the proposed model is accurately applied to large and small piezoelectric coupling conditions. The piezoelectric cantilever with large piezoelectric and EMC coefficients can be accurately analyzed by the proposed model accounted for small EMC condition in a traditional model. Design optimization based on actuators is also discussed. Optimal thickness ratios between elastic and piezoelectric layers are effectively calculated and obtained. [ABSTRACT FROM AUTHOR]

Purpose The purpose of this paper is to design a low-cost stress bimorph RF-MEMS switch which is the desired transmission area application.Design/methodology/approach The bimorph structure of the low-temperature plasma-enhanced chemical vapor deposition (PECVD) of thermal oxide and gold are utilized to create the vibrating membrane. The effects of process conditions of low-temperature oxide deposited using the PECVD technique enable stress-free deposition of the key structural layer.Findings Scanning electron microscope images of the RF micro-switch confirms negligible stress in the released structure. The RF performances of this device exhibit isolation around 43 dB of up to 50 GHz in the OFF-state position and an insertion loss of less than 0.18 dB in the ON-state.Originality/value The finite element method results show good isolation of 43 dB and less insertion loss of 0.18 dB. [ABSTRACT FROM AUTHOR]

• A theory is provided for piezoelectricity of a film on a flexible substrate with isotropic lattice mismatch. • Attribution of DBLI signal to thickness change of the thin film only is erroneous. • Contributions of the substrate and the film to piezoelectric response are comparable in magnitude. • Piezoelectric response is calculated for relevant ferroelectrics depending on substrate thickness. Advanced micro- and nano-electro-mechanical systems benefit from single-crystal-type epitaxial piezoelectric films, whose high crystal quality ensures excellent performance. Strong mechanical coupling in such films to non-piezoelectric substrates defines a difference in their operation with respect to purely piezoelectric counterparts. This is often described by a limiting case of a thick non-deformable substrate, whereas the film has out-of-plane deformations only. Here we consider a general practically relevant case, when converse piezoelectric effect in the film causes bending of the substrate. We provide a thermodynamic description and deliver analytical expressions for curvature, stress release, and thickness changes in a stack of the parallel-plate thin-film capacitor coherent to the substrate. It is shown that substrate deformations cannot be neglected and the d 33 piezoelectric modulus receives comparable contributions from the film and the substrate. Implications for the interferometric measurement of the converse piezoelectric response are discussed. [ABSTRACT FROM AUTHOR]

This paper proposes a new design of multilayered bimorph electrothermal actuators based on a Ni and Co alloy (Ni–Co) substrate and analytical models to estimate their performance. The proposed bimorph actuator consists of a flexible Ni–Co substrate having high coefficient of thermal expansion (CTE) along with two insulation (low-CTE materials) and Pt heater layers. A multilayered thermo-mechanical model to estimate the tip deflection was derived based on Timoshenko's classical model for metal bilayers. An analytical model based on the Euler–Bernoulli beam theory was also derived to calculate the blocking force of the multilayered actuators. An appropriate layer composition of the low-CTE layers was derived based on the analytical models and lattice parameters of the adjacent layers: the performance of the bimorph actuator was significantly improved when the low-CTE layers are composed of a dual layer instead of a single layer of SiO 2. The analytical solutions of the simplified 3D models were then compared with finite element analysis (FEA) and experimental results. In the comparison of the tip deflection, the analytical solution of the three-layer actuator omitting the Pt heater was similar to the FEA result and the experimental result compensating for the initial dead zone. In the comparison of the blocking force, the analytical solution was also similar to the FEA results, though there was a deviation from the experimental results. Abnormal behavior of the actuator was observed in the experimental result of the blocking force, and the cause was investigated in this study. [Display omitted] [ABSTRACT FROM AUTHOR]

Beam shaping is becoming increasingly important for synchrotron X-ray applications. Although routine for visible light lasers, this is challenging for X-rays due to the limited source coherence and extreme optical tolerances required for the shaping mirrors. In deliberate defocusing, even surface errors <5 nm r.m.s. introduce damagingly large striations into the reflected beam. To counteract such problems, surface modifications with alternating concave and convex curvature on equal segments were polished onto the surface of non-active mirrors of fixed curvature. Such optics are useful for providing a fixed size of X-ray beam, but do not provide the adaptability required by many experiments. In contrast, deformable piezo bimorph mirrors permit a continuous range of X-ray beam sizes and shapes. A new theory is developed for applying non-periodic modifications of alternating curvature to optical surfaces. The position and length of the segments may be freely chosen. For the first time, surface modifications of alternating curvature are applied to bimorph mirrors to generate non-Gaussian X-ray beam profiles of specified width. The new theory's freedom is exploited to choose the segments to match the polishing errors of medium wavelength (>10 mm) and the piezos' influence on the mirror's figure. Five- and seven-segment modifications of alternating curvature are calculated and verified by visible light and X-ray metrology. The latter yields beam profiles with less striation than those made by defocusing. Remaining beam striations are explained by applying geometrical optics to the deviations from the ideal surface modifications of alternating curvature. [ABSTRACT FROM AUTHOR]

We present an analytical model to analyze the bending of a bimorph beam comprising of piezoelectric material (PM) and shape memory alloy (SMA) thin layers. The model starts from the governing equations of the bending beam based on the Euler-Bernoulli beam theory. The PM and SMA layers are supposed to be perfectly bonded. The linear constitutive equations of PMs are used. Using this approach, we investigate thermal energy conversion into electricity by mean of the SMA-PM bimorph. Particularly, the model takes into account cyclic thermal energy harvesting by coupling the direct piezoelectric effect and the two-way shape memory effect. In this case, the SMA is assumed to be trained prior to assembling the bimorph so that it can deform in a cyclic way upon cyclic thermal loading without applying any external stress. The thermal-to-electrical conversion is achieved from the induced strain within the SMA layer upon heating which induces stress into the PM layer so that it produces an electrical potential. [ABSTRACT FROM AUTHOR]

This paper examines a passive cooling technique using microelectromechanical systems (MEMS) for localized thermal management of electronic devices. The prototype was designed using analytic equations, simulated using finite element methods (FEM), and fabricated using the commercial PolyMUMPs™ process. The system consisted of an electronic device simulator (EDS) and MEMS bimorph cantilever beams (MBCB) array with beams lengths of 200, 250, and 300 μm that were tested to characterize deflection and thermal behavior. The specific beam lengths were chosen to actuate in response to heating associated with the EDS (i.e. the longest beams actuated first corresponding to the hottest portion of the EDS). The results show that the beams deflected as designed when thermally actuated and effectively transferred heat away via thermal conduction. The temperature when the beams reached 'net-zero' deflection (i.e. uncurled and flat) was related to the initial deflection distance while the contact deflection temperature and rate of actuation was related to beam length. Initial beam deflections, after release, and contact temperatures, when fully actuated, were approximately 5.05, 9.45, 14.05 μm, and 231, 222, 216 °C, respectively with the longer beams making contact first. This innovative passive thermal management system enables selective device cooling without requiring active control or forced convection to maintain steady-state operating temperatures for sensitive microelectronic devices. [ABSTRACT FROM AUTHOR]

Extracting energy from low vibration frequencies (<10 Hz) using piezoelectric energy harvester promises continuous self-powering for sensors and wearables. The piezoelectric compliant mechanism (PCM) design provides a significantly higher efficiency by fostering a uniform strain for its 1st mode shape, and so is interesting for this application. In this paper, a PCM energy harvester with bimorph Pb(Zr,Ti)O3 (PZT) films on Ni foil deposited by rf magnetron sputtering is shown to have high efficiency and large power for low frequency mechanical vibration. In particular, {001} textured PZT films are deposited on both sides of polished Ni foils with (100) oriented LaNiO3 seed layers on HfO2 buffer layers. The performance of PCM with an active area of 5.2 cm2 is explored for various excitation accelerations (0.02-0.16 g [g = 9.8 m s−2]) around 6 Hz. The PCM device provides a power level of 3.9 mW cm−2 g2 and 65% mode shape efficiencies. [ABSTRACT FROM AUTHOR]

This paper presents the concept, basic theory, fabrication, and testing results of dual-electrode bimorph piezoelectric micromachined ultrasonic transducers (pMUTs) for both air- and liquid-coupled applications. Both the theoretical analyses and experimental verifications under the proposed differential drive scheme display high drive sensitivity and an electromechanical coupling energy efficiency that is as high as 4\times of the state-of-the-art pMUT with a similar geometry and frequency. The prototype transducers are fabricated in a CMOS-compatible process with the radii of 100–230 \mu \text{m} using aluminum nitride as the piezoelectric layers with the thicknesses varying from 715 to 950 nm and molybdenum (Mo) as the electrodes with a thickness of 130 nm. The tested operation frequencies of the prototype transducers are 200–970 kHz in air for possible ranging and motion detection applications, and from 250 kHz to 1 MHz in water for medical ultrasound applications such as fracture healing, tumor ablation, and transcranial sonothrombolysis. A 12\times 12 array structure is measured to have the highest intensity per voltage squared, per number of pMUTs squared, and per piezoelectric constant squared ( In= I/(VNd31)^{2}) among all reported pMUT arrays. The generated acoustic intensity is in the range of 30–70 mW/cm2 up to 2.5 mm from the transducer surface in mineral oil with a driving voltage of 5 \text{V}{\mathrm{ac}} , which is suitable for battery-powered therapeutic ultrasound devices. [2015-0305] [ABSTRACT FROM PUBLISHER]

Functionally graded piezoelectric (FGP) material removes the brittleness issue of piezoceramics and small coupling coefficient of piezoelectric polymers. They also avoid the stress concentration and consequently crack propagation. This work addresses the finite element modeling of the functionally graded piezoelectric harvesters subjected to random vibrations. The finite element electro-mechanical governing equations of FGP beam are derived by using the generalized Hamilton’s principle under the assumptions of Euler–Bernoulli beam theory. The material properties of the beam are assumed to be varied in the thickness direction following a simple power law distribution. The random base excitation of FGP harvester is assumed to be the Gaussian white noise signal. Both time domain and frequency domain analysis are presented in this work. In the numerical analysis presents the effects of electrical load resistance value, the volume fraction of the piezoelectric material and the PSD level of base acceleration on the expected power output of the piezoelectric harvester are investigated. Numerical results show that a functionally graded reinforcement has a significant influence on the output voltage and the harvested power of the beams. Moreover, the output power increases linearly by increasing PSD level of base acceleration. The results also confirm that time domain and frequency domain analysis results are in good agreement with each other. [ABSTRACT FROM AUTHOR]

Multiferroic composites with ferromagnetic and ferroelectric phases have been studied in recent years for use as sensors of AC and DC magnetic fields. Their operation is based on magneto-electric (ME) coupling between the electric and magnetic subsystems and is mediated by mechanical strain. Such sensors for AC magnetic fields require a bias magnetic field to achieve pT-sensitivity. Novel magnetic sensors with a permanent magnet proof mass, either on a ferroelectric bimorph or a ferromagnetic-ferroelectric composite, are discussed. In both types, the interaction between the applied AC magnetic field and remnant magnetization of the magnet results in a mechanical strain and a voltage response in the ferroelectric. Our studies have been performed on sensors with a Nd-Fe-B permanent magnet proof mass on (i) a bimorph of oppositely-poled lead zirconate titanate (PZT) platelets and (ii) a layered multiferroic composite of PZT-Metglas-Ni. The sensors have been characterized in terms of sensitivity and equivalent magnetic noise N. Noise N in both type of sensors is on the order of 200 pT/√Hz at 1 Hz, a factor of 10 improvement compared to multiferroic sensors without a proof mass. When the AC magnetic field is applied at the bending resonance for the bimorph, the measured N ≈ 700 pT/√Hz. We discuss models based on magneto-electro-mechanical coupling at low frequency and bending resonance in the sensors and theoretical estimates of ME voltage coefficients are in very good agreement with the data. [ABSTRACT FROM AUTHOR]

Our study describes the fabrication of thermal actuation with a bimorph film of PVDF/rGO composites and polyimide film, exploiting the large difference in the thermal expansion coefficients of the two films. We performed the thermo-mechanical and XRD characterization of the obtained PVDF/rGO composites. The analyses indicate that the novel composites have enhanced mechanical strength and higher portion of β-phase crystallinity as compared to those of pure PVDF. To fabricate the bimorph for thermal actuation, the solution of PVDF/rGO composites is simply casted on a polyimide film. Thereafter, we evaluate their mechanical displacement using a temperature stimulus. However, in case of pure PVDF sample, a limited and permanent displacement is observed when subsequent cycles of thermal actuation test are performed, the PVDF/rGO samples exhibit a superior controlled displacement as they regained their original shape completely, even after being subjected to the repeated heating/cooling cycles. On the basis of control experiments and XRD study, the possible mechanism is suggested that the PVDF/rGO composites show excellent characteristics of thermal actuation as they are associated with a reversible transformation of crystalline phase and the enhanced mechanical strength in the presence of rGO in the composites. [ABSTRACT FROM AUTHOR]

Vanadium dioxide VO 2 nanowire bimorph actuators work on the basis of the large abrupt length change at the metal-insulator phase transition (MIT). A key parameter for the bimorph performance and efficiency is the bending curvature and the width of the temperature hysteresis of the MIT which is inherently large for single domain VO 2 metal side coated nanowires. In this work we present single-clamped Ir side coated VO 2 bimorphs which show unprecedented high bending curvatures of up to 10 5 m −1 and new type of side ion-implanted VO 2 nanowire bimorph actuators with a nearly completely suppressed temperature hysteresis. It is assumed that ion-beam induced radiation defects in the VO 2 crystal structure act as nucleation sites for the MIT. Moreover it will be shown that mechanical strain intentionally built-in during VO 2 nanowire bimorph fabrication allows to direct phase transformation via a strain stabilized metastable phase and thus allows to control bending response on temperature change. [ABSTRACT FROM AUTHOR]

This article describes a new electrical configuration for driving piezoelectric benders. The ‘Biased Bipolar’ configuration is compatible with parallel-polled, bimorph and multimorph benders. The new configuration is similar to the standard three-wire drive method where the top electrode is biased with a DC voltage and the bottom electrode is grounded. However, the new configuration uses an alternate DC bias voltage and adjusted range for the central electrode which allows the full range of positive and negative electric fields to be utilized. Using this technique, the predicted deflection and force can be increased by a factor of 2.2 compared to the standard two wire configuration and 1.3 times for the standard three wire configuration. These predictions were verified experimentally where the measured factor of improvement in displacement and force was of 2.4 and 1.3 compared to the standard two-wire and three-wire configurations. [ABSTRACT FROM AUTHOR]

SUMMARY In order to realize a vibration sensor, which can operate without power supply, an optimization of the sensor configuration was studied using commercial piezoelectric bimorphs. The dependences of the energy conversion efficiency on the weight of metal mass attached to the tip of the piezoelectric bimorph and peripheral circuit components were investigated. Vibration sensors using several piezoelectric bimorphs with different weights were designed, fabricated, and tested. [ABSTRACT FROM AUTHOR]

This study presents the development of a miniature wind turbine that can be used for powering wireless sensors deployed at remote locations. The wind turbine utilizes piezoelectric transducers in order to reduce the start-up speed. Six piezoelectric bimorphs with magnetic tip mass were actuated through attractive and repulsive force between permanent magnets. The design and characterization of the prototype is discussed along with a Finite Element Model (FEM) of the piezoelectric elements. The wind turbine was 23 cm high and 16.5 cm wide. It was able to achieve low cut-in speeds of 1m/s providing power outputs ranging between 0.5 mW and 3 mW for wind speeds in the range of 1 m/s to 4 m/s. [ABSTRACT FROM PUBLISHER]

Highlights: [•] A new MEMS-based 3D confocal scanning microendoscope has been designed, constructed and experimentally verified. [•] The compact fiber-optic endoscopic probe integrates the MEMS scanners, fiber and high-quality micro-optics. [•] Both lateral scan and axial scan are performed by MEMS devices with large scan ranges and low drive voltages. [•] Polarization sensitive components have been employed to suppress unwanted reflections. [•] 2D and 3D confocal reflectance images of various samples have been obtained with high resolutions. [ABSTRACT FROM AUTHOR]

Simple and effective new type of tactile device is presented and investigated, which transfers 2D graphic information to the visually impaired people. It consists of piezoelectric bimorph cantilever, acting as an oscillating probe, and, when changing operational signal, could transfer information to visually impaired people, e.g. by crossing the lines/contours on the screen of tablet PC or determining the color of them. Determining the amplitude of tip's oscillation, attached to bimorph PZT cantilever and contacting with finger, is presented. It is established that tactile device's body and integrated bimorph cantilever oscillations and their effect on the human finger are different. The visually impaired people better percept the oscillations of Braille pins, which are attached to cantilever tip; maximum perception of tip's oscillations are achieved, when bimorph tip generates approximately 0.5 N force. [ABSTRACT FROM AUTHOR]

Due to their capability to convert mechanical energy directly to electrical energy, piezoelectric energy harvesters have become a new powering choice for many electronic devices. This work demonstrates piezoelectric energy harvester systems operating in environments ranging from room temperature up to 82°C and compares their performance using different piezoelectric materials. The systems are structured with a PMN-PT (lead magnesium niobate-lead titanate) single crystal patch bonded to an aluminum cantilever beam, PIN-PMN-PT (lead indium niobate-lead magnesium niobate-lead titanate) single crystal patch bonded to an aluminum cantilever beam and a bimorph cantilever beam which is made by lead zirconate titanate (PZT). The results show that temperature has affected the output power of the energy harvesting system in a complex way and shifted the resonance frequency to a lower value. The results provide an invaluable reference for energy harvesting in harsh environments. [ABSTRACT FROM AUTHOR]

Piezoelectric energy harvesters are ideal for capturing energy from mechanical vibrations in the ambient environment. Numerous studies have been made of this application of piezoelectric energy conversion; however, thus far researchers have encountered limitations in the amount of power that can be captured. In this paper, a frequency- adjustable energy harvester with an array of piezoelectric bimorphs connected by springs has been designed and analyzed based on the 1D piezoelectric beam equations. The result shows that the energy harvester is capable of operating in multiple frequencies, and the operating frequencies can be adjusted by changing the small end masses and spring stiffness. An optimal selection of the load impedance to realize the maximum power output is discussed. The power efficiency of the energy harvester has been analyzed as well. [ABSTRACT FROM AUTHOR]

A large displacement piston motion micromirror is designed, fabricated, and tested with device features tuned to applications requiring ultralow tilt. The fabricated MEMS mirror is based on electrothermal actuation and has a footprint of 1.9 mm × 1.9 mm with a mirror aperture of 1 mm. The application optimized device holds key features of ultralow maximum tilt of 0.25 ° and a strongly linear motion of 90 μm achievable at only 1.2 V. This device is further characterized in an interferometric system to determine the piston mode and the accurate piston displacement as a function of voltage, power, and frequency. [ABSTRACT FROM AUTHOR]

Piezoelectric bimorph based on k32 mode of ternary 0.24Pb(In1/2Nb1/2)O3-0.46Pb(Mg1/3Nb2/3)O3-0.30PbTiO3 (0.24PIN--0.46PMN--0.30PT) single crystal poled along [011] c has been fabricated and tested. The bimorph features very large electromechanical coupling factor (0.80) and very low working frequency (less than half of PZT based bimorph for the same dimensions) owing to the super large lateral extensional piezoelectric constant d32 and large elastic compliances [ABSTRACT FROM AUTHOR]

Piezoelectric bimorphs have been used as a micro-gripper in many applications, but the system might be complex and the response performance might not have been fully characterized. In this study the dynamic characteristics of bending piezoelectric bimorphs actuators were theoretically and experimentally investigated for micro-gripping applications in terms of deflection along the length, transient response, and frequency response with varying driving voltages and driving signals. In addition, the implementation of a parallel micro-gripper using bending piezoelectric bimorphs was presented. Both fingers were actuated separately to perform mini object handling. The bending piezoelectric bimorphs were fixed as cantilevers and individually driven using a high voltage amplifier and the bimorph deflection was measured using a non contact proximity sensor attached at the tip of one finger. The micro-gripper could perform precise micro-manipulation tasks and could handle objects down to 50 µm in size. This eliminates the need for external actuator extension of the microgripper as the grasping action was achieved directly with the piezoelectric bimorph, thus minimizing the weight and the complexity of the micro-gripper. [ABSTRACT FROM AUTHOR]

Piezoelectric pumps have the potential to be used in a variety of applications, such as in air circulation and compression. However, piezoelectric membrane pumps do not have enough driving capacity, and the heat induced during the direct contact between the driving part and the gas medium cannot be dissipated smoothly. When the gas is blocked, the piezoelectric vibrator generates heat quickly, which may eventually lead to damage. Resonantly driven piezoelectric stack pumps have high performance but no price advantage. In this situation, a novel, resonantly driven piezoelectric gas pump with annular bimorph as the driver is presented. In the study, the working principle of the novel pump was analyzed, the vibration mechanics model was determined, and the displacement amplified theory was studied. The outcome indicates that the displacement amplification factor is related with the original displacement provided by the piezoelectric bimorph. In addition, the displacement amplification effect is related to the stiffness of the spring lamination, adjustment spring, and piezoelectric vibrator, as well as to the systematic damping factor and the driving frequency. The experimental prototypes of the proposed pump were designed, and the displacement amplification effect and gas output performance were measured. At 70 V of sinusoidal AC driving voltage, the improved pump amplified the piezoelectric vibrator displacement by 4.2 times, the maximum gas output flow rate reached 1685 ml/min, and the temperature of the bimorph remained normal after 2000 hours of operation when the gas medium was blocked. [ABSTRACT FROM AUTHOR]

Abstract: We present an electrostrictive polymer bimorph controllable with low voltage through an integrated CMOS OFET control system. We have actuated the device by applying voltages up to 400V to the control system, and can actuate the control with 60V switching. The electrostrictor material was used both as the substrate for the transistors and as the dielectric layer for the control circuitry. This allows for a reduction in the number of layers in the structure, minimizing the clamping effect that would compromise the strain capabilities of the device. We have characterized the macroscopic displacement of the structure through a radius of curvature measurement, ranging from 11.4mm to 7.5mm depending on the supply voltage provided. The architecture proposed can be scaled to larger system with higher supply voltages. [Copyright &y& Elsevier]