Electromechanical Resonance Research Articles

Physics of Composites for Low-Frequency Magnetoelectric Devices.

The article discusses the physical foundations of the application of the linear magnetoelectric (ME) effect in composites for devices in the low-frequency range, including the electromechanical resonance (EMR) region. The main theoretical expressions for the ME voltage coefficients in the case of a symmetric and asymmetric composite structure in the quasi-static and resonant modes are given. The area of EMR considered here includes longitudinal, bending, longitudinal shear, and torsional modes. Explanations are given for finding the main resonant frequencies of the modes under study. Comparison of theory and experimental results for some composites is given.

Tutorial: Piezoelectric and magnetoelectric N/MEMS—Materials, devices, and applications

Nano- and micro-electromechanical systems (N/MEMSs) are traditionally based on electrostatic or piezoelectric coupling, which couples electrical and mechanical energy through acoustic resonator structures. Most recently, N/MEMS devices based on magnetoelectrics are gaining much attention. Unlike electrostatic or piezoelectric N/MEMS that rely on an AC electric field or voltage excitation, magnetoelecric N/MEMS rely on the electromechanical resonance of a magnetostrictive/piezoelectric bilayer heterostructure exhibiting a strong strain-mediated magnetoelectric coupling under the excitation of a magnetic field and/or electric field. As a consequence, magnetoelectric N/MEMS enable unprecedented new applications, ranging from magnetoelectric sensors, ultra-compact magnetoelectric antennas, etc. This Tutorial will first outline the fundamental principles of piezoelectric materials, resonator design, specifically different acoustic modes, and piezoelectric-based N/MEMS applications, i.e., radio frequency front end filters and infrared radiation sensors. We will then provide an overview of magnetoelectric materials and N/MEMS focusing on the governing physics of the magnetoelectric effect, magnetic material properties for achieving high magnetoelectric coupling, state-of-the-art magnetoelectric N/MEMS devices, and their respective applications.

Design aspects of shape memory wire based resonant force measurement system

Appropriate design of the components of a sensing system affords high degree of performance characteristics; this article presents the design optimization of a novel force measurement strategy created using shape memory alloy (SMA) wire using the resonance principle. SMAs are unique materials that are generally used to realize actuators and dampers in instrumentation systems, now will be found in sensors too. A resonant sensing mechanism is realized using an SMA wire with gravity bias and, its co-acting flexible member the cantilever beam. The operating phenomenon is based on the shift in resonant frequency corresponding to an applied force, and the sensing module detects force in the range of few newtons. Design procedures of the sensor are realized, the modes of the physical realization are modeled using lumped parameter technique and the force measurement system using the electromechanical resonator is validated from the experimental measurements and analytical results.

Actively tuning of transverse wave band gaps in hybrid sandwich beam metamaterials with shunted piezoelectric array and inertial amplification mechanism

In this paper, a tunable sandwich beam metamaterial is designed by implementing a hybrid project composed of the piezoelectric shunted array technique and the inertial amplification mechanism. Concerned with the shunted piezoelectric constitutive relation, the kinematic analysis of added mechanism and the transverse motion of base structure, a theoretical model is established to estimate the band gap characteristics of the sandwich beam lined with pyramidal truss cores using the transfer matrix method, whose accuracy is further validated by the finite element simulations. Numerical results show that multiple stop bands are generated at low frequencies owing to the mechanisms of electromechanical resonance, amplifying inertia and mechanical resonance, certainly enhancing the level of vibration suppression. Subsequently, a comprehensive parametric analysis is conducted to investigate the influences of the shunting circuits and attached mechanism on the attenuation diagrams. It is demonstrated that the hybrid sandwich lattice can offer more tunable space to acquire ultra-broad band gaps. Furthermore, based on the design potential, the amplitudes and bandwidths of the attenuation region are maximized by operating an optimization study. Such advanced attenuation performance can be applied for a wide range of engineering applications.

Double-Gate Vectorial Frequency Control in Piezoresistive Nanowire Electromechanical Devices

Vacuum-gap and orthogonally aligned double-gate geometry is employed in a nanowire-based electromechanical resonator device to independently control two nearly degenerate orthogonal vibration modes. In the device, piezoresistance is the dominant mechanism of motion-induced conductance variation, which provides an efficient scheme for the self-transduction of vibrational motion into an electric signal. Two simultaneously applied gate voltages induce an opposite combined effect on the frequency shift between two vibration modes, which is well explained by model calculations. Using the opposite double-gate effect, we demonstrate vectorial control of two mode frequencies, which is not possible with single-gate geometry.

Multilevel Frequency-Specific Information Storage Using Engineered Electromechanical Resonances in Piezoelectric Wafer Arrays.

Multilevel information storage methods have the potential for increasing storage density and improving information security through obfuscation. Taking inspiration from the color quick response codes, we have developed a method for encoding layers of information in an array of thin piezoelectric wafers. Information storage is accomplished by altering the size of the circular polarization domain of individual wafers to engineer the response of the electromechanical resonances. By using this approach, we can store one layer of information per electromechanical resonance. In this study, we experimentally demonstrate this approach on a 20-element piezoelectric wafer array with up to two layers of information storage using binary encoding. We first discuss the relevant theory behind the proposed approach and the method for designing the polarization profiles for these wafer arrays to enable multilevel information storage. The effect of the size of the polarization domain on the strength of the electromechanical resonances and optimal size to enhance/suppress these resonances is discussed. Last, we describe how the proposed approach could be used to encode four or more layers of frequency-specific information. The proposed technology finds application in embedded barcodes, product tags, tamper-evident seals, and other secure applications such as shipping sensitive materials/containers.

Low-Frequency Magnetic Field Detection Using Magnetoelectric Sensor With Optimized Metglas Layers by Frequency Modulation

It is an important engineering challenge to detect a weak magnetic field <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${H}_{AC}$ </tex-math></inline-formula> at low frequencies (1-100 Hz) due to large noise. In this work, a magnetoelectric (ME) sensor using single-crystal quartz material as the piezoelectric phase and optimized magnetostrictive layers has been presented to sense the low-frequency magnetic field signals. Firstly, the ME response properties of the bulk Metglas/quartz/Metglas laminate sensor were studied and a high ME coefficient of 3038 V/(cm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\cdot $ </tex-math></inline-formula> Oe) has been attained in its electromechanical resonance frequency. With frequency modulation technique, which a magnetic low-frequency signal can be transferred to around resonance frequency of the sensor, the proposed sensor was used to detect the low frequency magnetic field signals under zero bias conditions. It is experimentally found that the absolute resolution with respect to a 1 Hz magnetic field can be decreased as low as 44 pT ± 1.41 pT with 20 layers of Metglas. More importantly, the ME coefficients with different layers under zero bias and the effect of Metglas layers on the limit of the detection at 1 Hz also have been investigated. The results show that the limit of the detection at 1 Hz can be decreased to 10 pT ± 0.32 pT with 14 layers of Metglas which indicates an enhancement by 4.4 times in comparison with 20 layers. This simple bulk Metglas/quartz/Metglas laminate sensor with optimized layers has a great potential to be used for low-frequency bio-magnetic signals measurement at room temperature.

Research progress of electromechanical graphene resonant sensors

The resonant sensor is a kind of high-sensitivity and high-stability sensor that directly outputs digital signals. The resonance sensitive elements of traditional resonant sensors are mostly made of metal, quartz crystal, silicon and other materials. However, with the development of resonant sensor toward the miniaturization and intellectualization, the sensitive materials of new resonator are micro-nano machined and highly sensitive. As a new type of two-dimensional nanomaterial, graphene has the great potentials in the field of resonance sensing because of its excellent mechanical, electrical, optical and thermal properties. Therefore, the mechanical quantity sensor based on graphene material is expected to surpass the silicon material mechanical quantity sensor in many aspects such as micro-nano size, high performance, and environmental adaptability. This review focuses on the graphene resonant mechanical quantity sensor. In the first part, we summarize the basic properties, preparation methods, and transfer methods of graphene materials. The preparation and transmission methods of graphene are key to high-performance graphene resonator, but there are still different problems in the preparation and transfer of graphene, which also greatly restricts the development of graphene resonator. In the second part, the basic theory of resonant sensors is given, and the common methods of transferring graphene films are introduced in detail. Then the theoretical and experimental studies of graphene resonator are discussed. For example, the theoretical studies of graphene resonator are investigated by using the classical elastic theory, non-local elastic theory, molecular structure mechanics and molecular dynamics. Then the effects of graphene preparation method, graphene layer number and shape, excitation and detection methods on the resonance performance are estimated in the resonant experiments of graphene resonators. After that, the research progress of graphene resonator is summarized in the fields of pressure, acceleration and mass sensors. Compared with traditional silicon resonators, graphene resonators have a small dimension and demonstrate preferable resonant performance under low-temperature and low-pressure conditions. In this case, the technical issues of graphene resonant sensor are introduced to emphasize the importance of suspended graphene film transfer, structure fabrication of harmonic oscillator and vibration excitation/detection of resonators, which contributes to the potential applications in the fields of aerospace, intelligent detection and biomedical sensing for graphene resonant sensors.

Performance Analysis of Resonant-Fin Transistors and Their Application in RF-Circuit Design

Emerging new communication standards like 5G or 6G aggravate the circuit design of radio-frequency generation systems as they constantly increase demand on high bandwidths, low latency, and high spectral purity. The utilization of high-<i>Q</i> oscillators, however, provides a possibility of optimisation of radio-frequency oscillators regarding their phase-noise performance in the overall system. This paper analyses one of the most promising electromechanical resonator devices, the resonant fin transistor with respect to its performance and application in oscillator circuit design. Several investigations regarding its working principle, design trade-offs and limits are carried out in this work. An oscillator circuit design is given for two variants of the resonant fin transistor device together with an outlook on its performance compared to other state-of-the-art radio-frequency oscillator designs. Following the performance analyses conducted throughout this work, the fundamental limit for the <i>Q</i>-factor of this resonator is investigated, challenging the validity of functionality of the resonant fin transistor and its potential for circuit applications.

Tuning the Relative Strengths of Electromechanical Resonances Using Non-Uniform Polarization of Piezoelectric Wafers

Tuning the Relative Strengths of Electromechanical Resonances Using Non-Uniform Polarization of Piezoelectric Wafers

Electromechanical response of laterally clamped piezoelectric wafers: Absence of in-plane mechanical resonances in the electromechanical impedance spectrum

We discuss the electromechanical response characteristics of laterally clamped piezoelectric wafers. The impedance spectra (both magnitude and phase) obtained from finite element simulations of uniformly polarized free and clamped circular and square wafers are first presented. It is observed that the magnitude and phase of the impedance spectrum for free piezoelectric wafers shows all the in-plane extensional modes as electromechanical resonances, while that for a clamped wafer does not show any of them. However, it is also shown that the spectrum corresponding to the out-of-plane displacement on the surface of the wafer actually shows the in-plane resonances for both free and clamped wafers. In other words, it is found that the clamped wafer shows in-plane mechanical resonances but these do not appear in the electromechanical impedance spectrum. This observation is then generalized and explained using an analytical model for thin piezoelectric wafers of arbitrary shape. In particular, it is shown that the impedance spectrum of laterally clamped piezoelectric wafers of any arbitrary shape do not show in-plane extensional modes as electromechanical resonances. Moreover, the impedance spectrum of a laterally clamped wafer is shown to depend only on its area and thickness but not its shape. The above findings are relevant to measurement techniques that rely explicitly on the characteristics of the impedance spectrum observed for a piezoelectric wafer. In addition, the absence of resonances resulting from lateral clamping allows for broadband operation of piezoelectric wafers as sensors and actuators for applications such as ultrasonic range finding, underwater acoustics and acoustic imaging.

The electromechanical damping of piezo actuator resonances: Theory and practice

Piezo actuators have very desirable properties, such as a high stiffness and extreme position resolution, but suffer from electromechanical resonances that complicate their use in high-speed applications. These resonances can be minimized by using resistive or resistive-inductive damping.In this paper a comprehensive theory is presented which describes these piezo resonances, and the mechanism by which these resonances are minimized by adding electrical damping components. The theory is based on a purely electronic model, and uses an electrical-mechanical transformation to describe actual piezo displacements. Using this theory, an ‘optimal’ value of damping resistance is readily identified. This optimal resistance causes maximal damping of the primary resonance of the piezo. It is shown that damping with a combination of a resistor and an inductor can theoretically be even better.An optical displacement setup was developed, and frequency- and time-domain measurements were performed that validate the theory. The mechanical damping of the piezo actuator needs to be included in the theory to obtain a good fit with the electrical and mechanical behavior of an actual piezo actuator.

Comparative theoretical study of the resonance frequencies of the longitudinal-shear and torsion modes of the magnetoelectric effect in a two-layer magnetostrictive-piezoelectric structure Metglas / GaAs

The article is devoted to a comparative theoretical study of the frequencies of the electromechanical resonance (EMR) of the magnetoelectric (ME) effect in the magnetostrictive-piezosemiconductor structure Metglas / GaAs of the longitudinal-shear and torsional modes. It is found that the resonance frequencies for the torsional mode are approximately 2 times higher than the corresponding frequencies for the longitudinal-shear mode. Therefore, it is quite possible to observe the torsional mode of the ME effect against the background of the longitudinal-shear mode, since the resonance frequencies are well distinguishable. The results obtained can find application in the construction of new ME devices.

Finite element simulation and characterization of one-port heterostructured surface acoustic wave resonator

The research work presents the study of a heterostructured surface acoustic wave (SAW) resonator consisting of an interdigital transducer (IDT), lithium niobate (LN), and silicon (Si) substrate. In the proposed structure, Silicon is the base substrate, above it layer of LN is placed then IDT is designed on it. The presented analysis includes the variation of the quality factor and electromechanical coupling coefficient with the change in the width of the piezoelectric layer. The electromechanical coupling coefficient (K 2), quality factor (Q-factor), velocity, resonance, admittance, and anti-resonance frequency have been studied for the thickness of the different layers of LN film. The higher quality factor of one port SAW devices reduces the energy loss and the K 2 of the devices indicates faster energy conversion. The Q-factor and K 2 are found to be depending on the thickness of LN, resonance, and anti-resonance frequency.

Multi-order phononic frequency comb generation within a MoS2 electromechanical resonator

In this work, we measure and tune simultaneously the vibration of a 1-nm thick MoS2 suspended monolayer with standard electrical excitation and optical techniques. At ambient temperature, we first investigate the strong parametric coupling between two different mechanical modes (ω1 and ω2). We demonstrate a high and quasi-linear tunability of the mode frequencies with the parametric pump voltage. Then, we couple the highly tunable main vibration (ω1) to a parametric pump frequency (ωp) to obtain a high number of sidebands at frequencies ω1 ± m ωp, driving the mechanical mode with a large external electrical force. This oscillating force, applied via the gate voltage, acts as a stress onto the MoS2 sheet. The obtained frequency comb has a large spectral band and contains up to 100 harmonics, with potential applications in quantum information processing and heat or sound transport.

Studies of a new-style resonator to control electro-mechanical coupling bandgap of a locally resonant piezoelectric/elastic phononic crystal double-layer nonlocal nanobeam

The paper proposed a model of a locally resonant (LR) piezoelectric/elastic phononic crystal (PC) nanobeam with periodically attached “spring-mass” resonator and additional spring between upper and lower nanobeams, as well as horizontal spring between mass and foundation. Euler beam theory and nonlocal piezoelectricity theory are coupled and introduced to plane wave expansion (PWE) method to calculate the band structures of such a model with different parameters. Numerical results and further analysis demonstrate that all the bands of double-layer nanobeam can be divided into symmetric and antisymmetric ones. Adding additional and horizontal springs play a role in control the symmetric and antisymmetric bands respectively, which make wider band gaps be opened than corresponding single-layer nanobeam. Moreover, the change of parameters of electro-mechanical coupling fields and resonator can be applied to effectively control the starting frequencies and widths of band gaps, which can provide a theoretical basis for active control of vibration. Effects of geometric and non-dimensional nonlocal parameters on band gaps are also discussed. All the studies are expected to be applied to actively control vibration propagation in the field of nano electro-mechanical system (NEMS).

Effects of Oxide Additives on the Phase Structures and Electrical Properties of SrBi4Ti4O15 High-Temperature Piezoelectric Ceramics.

In this work, SrBi4Ti4O15 (SBT) high-temperature piezoelectric ceramics with the addition of different oxides (Gd2O3, CeO2, MnO2 and Cr2O3) were fabricated by a conventional solid-state reaction route. The effects of oxide additives on the phase structures and electrical properties of the SBT ceramics were investigated. Firstly, X-ray diffraction analysis revealed that all these oxides-modified SBT ceramics prepared presented a single SrBi4Ti4O15 phase with orthorhombic symmetry and space group of Bb21m, the change in cell parameters indicated that these oxide additives had diffused into the crystalline lattice of SBT and formed solid solutions with it. The SBT ceramics with the addition of MnO2 achieved a high relative density of up to 97%. The temperature dependence of dielectric constant showed that the addition of Gd2O3 could increase the TC of SBT. At a low frequency of 100 Hz, those dielectric loss peaks appearing around 500 °C were attributed to the space-charge relaxation as an extrinsic dielectric response. The synergetic doping of CeO2 and Cr2O3 could reduce the space-charge-induced dielectric relaxation of SBT. The piezoelectricity measurement and electro-mechanical resonance analysis found that Cr2O3 can significantly enhance both d33 and kp of SBT, and produce a higher phase-angle maximum at resonance. Such an enhanced piezoelectricity was attributed to the further increased orthorhombic distortion after Ti4+ at B-site was substituted by Cr3+. Among these compositions, Sr0.92Gd0.053Bi4Ti4O15 + 0.2 wt% Cr2O3 (SGBT-Cr) presented the best electrical properties including TC = 555 °C, tan δ = 0.4%, kp = 6.35% and d33 = 28 pC/N, as well as a good thermally-stable piezoelectricity that the value of d33 was decreased by only 3.6% after being annealed at 500 °C for 4 h. Such advantages provided this material with potential applications in the high-stability piezoelectric sensors operated below 500 °C.

Modification of Mechanical and Electromechanical Resonances of Cellular Ferroelectret Films Depending on the External Load.

Ferroelectret films are cellular polymers with electrically charged pores that exhibit piezoelectric response. Among other applications, ferroelectret films have been widely used as active elements in air-coupled ultrasonic transducers. More recently, they have also been tested in water immersion. They show a promising wide frequency band response, but a poor sensitivity produced by the disappearance of the electromechanical resonances. This paper studies in detail the modification of FE films response when put into water immersion, both the mechanical and the electromechanical responses (the latter in transmission and reception modes). The lack of electromechanical thickness resonances when the films are put into water is explained as the result of the different profile of the modification of the polarization vector along the film thickness imposed by the large mechanical load produced by the water. This different electromechanical response can also be the reason for the subtle modification of the mechanical thickness resonances that is also observed and analyzed.

Near-Zero Drift and High Electromechanical Coupling Acoustic Resonators at &gt; 3.5 GHz

In this article, near-zero drift and high electromechanical coupling acoustic resonators have been designed and demonstrated. The acoustic resonator is based on Lamb acoustic waves in a bimorph composed of lithium niobate on silicon dioxide. Our approach breaks through a performance boundary in conventional Lamb-wave resonators by introducing the bimorph while operating at higher order resonant modes. This enables the resonator to achieve frequency scalability, a low-temperature coefficient of frequency, and high electromechanical coupling altogether. The electromechanical coupling and temperature coefficient of the resonator were analytically optimized for the A <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> mode through adjusting the thicknesses of different materials in the bimorph. Resonators with different dimensions and stack thickness were fabricated and measured, resulting in a temperature coefficient of frequency ranging from -17.6 to -1.1 ppm/°C, high electromechanical coupling ranging from 13.4% to 18%, and quality factors up to 800 at 3.5 GHz. The achieved specifications are adequate for fifth-generation (5G) sub-6-GHz frequency bands n77 and n78.

Imaging vibrations of electromechanical few layer graphene resonators with a moving vacuum enclosure

Imaging the vibrations of nanomechanical resonators means measuring their flexural mode shapes from the dependence of their frequency response on in-plane position. Applied to two-dimensional resonators, this technique provides a wealth of information on the mechanical properties of atomically-thin membranes. We present a simple and robust system to image the vibrations of few layer graphene (FLG) resonators at room temperature and in vacuum with an in-plane displacement precision of ≈0.20 μm. It consists of a sturdy vacuum enclosure mounted on a three-axis micropositioning stage and designed for free space optical measurements of vibrations. The system is equipped with ultraflexible radio frequency transmission lines to electrically actuate resonators. With it we characterize the lowest frequency mode of FLG resonators by measuring its frequency response as a function of position on the membrane and by extracting its effective mass. We use the background noise of the undriven vibrational spectrum to calibrate in-plane displacement. Finally, we measure the first three vibration modes of a resonator whose membrane is partially folded and find that folds locally suppress vibrations.