Piezoelectric Disk Research Articles

Vibration energy harvesting with a clamped piezoelectric circular diaphragm

With the rapid development of low power devices, the technology of energy harvesting has improved greatly. The performance of a PZT diaphragm energy harvester is demonstrated in this paper. Under an acceleration of 9.8 m/s 2, a pre-stress of 1.2 N applied on the harvester, a power of 12 mW was generated at the resonance frequency of the harvester (113 Hz) across a 33 k ohm resistor. It was found that the energy from the harvester increases while its resonance frequency decreases when the pre-stress increasing. The contacting part between the proof mass and the piezoelectric disc was found another key element, which would influence the performance of the harvester. With its simple structure, the diaphragm harvester may push energy harvesting devices towards practical applications.

An analytical model of cymbal transducer dynamics. Radial vibration of a piezoelectric disc

This article represents the first step in an attempt to obtain an analytical model of a cymbal transducer. The structure is considered as two mechanically coupled systems (i.e. a piezoelectric disc producing radial motion and end caps amplifying under the compression caused by this radial behaviour). Therefore, an analytical model of the piezoelectric disc, core driver of the cymbal, and its dynamics under an electrical signal are presented in this article. The function describing the radial motion of the disc, distribution of the electrical potential along the thickness, and displacement along the thickness are obtained analytically. The obtained radial motion function will be used for modelling the end cap amplification as a compressive loading.

Modeling of an LFE piezoelectric fluid sensor as layered structure in the spectral domain

AbstractPiezoelectric fluid sensors with an LFE electrode arrangement (LFE: lateral field excitation — both electrodes are placed on one side of the disc) show unique differences compared to common thickness field excited (TFE) resonators, due to the additional lateral field components produced. In this contribution the LFE sensor setup is modeled as a layered structure in the spectral domain utilizing a semi-numerical approach. In particular the interaction of the piezoelectric disc and the sample liquid, which is too complex for analytical methods or too comprehensive for FEM, is efficiently modeled by the method. The calculation of the frequency responses as well as the electrical and the mechanical fields are illustrated. The simulation results are compared to results obtained from the Christoffel–Bechmann formalism, and sensitivities to fluid parameters like viscosity, density, and conductivity are shown. Furthermore, the sensitivity to viscosity is compared to experimental data.

Measurement of planar poisson’s ratio for piezoceramic disks.

Previous methods for a determination of a planar Poisson’s ratio in ferroelectric ceramic disks were proposed for thin disks. If a thickness of a disk strongly affects the vibrations, we get error in determination of Poisson’s ratio in usage 1-D theory of disk vibrations. Planar Poisson’s ratio in this work has been determined from an overtone method and a resonant method for a thick piezoceramic disk. The theoretical and the experimental contour modes with different types of vibrations symmetry have been compared in the resonant method. For the first theoretical contour mode the thickness correction was applied. The first order contour resonant frequency was determined in the experiment after the cutting of split electrodes. The overtone method is based on the solution of three-dimensional problem of vibrations of a finite cylinder. Only one experiment is needed in the overtone method. The obtained results have been compared with the handbook data. It may be concluded that the proposed methods provide an accurate determination of planar Poisson’s ratio in thick piezoelectric ceramic disks, when all experimentally measurements were made on the single piece of the piezoceramic material.

Non-axisymmetric radial vibrations of thin piezoelectric disks

The non axisymmetric radial oscillations of the thin piezoelectric disc is calculated in this paper. The zero approximation of the solution is provided as well

Principles of a micro squeeze flow rheometer for the analysis of extremely small volumes of liquid

In this paper, the analysis and design of a piezoelectrically actuated micro squeeze flow rheometer (MSFR) is presented. The fabrication of a simple prototype is described and initial experiments show the validity of the theory presented. The rheometer requires small volumes of liquid of the order of 1–10 nL and extends the frequency range an order of magnitude beyond that possible using conventional cone and plate rheometry. The electrodes of the piezoelectric disc which are used to actuate the rheometer have been patterned to allow the simultaneous measurement of the induced voltage, the phase and amplitude of which is then used to calculate the storage and loss moduli of the fluid being tested.

Evaluation of ultrasonic aluminium degassing by piezoelectric sensor

The purpose of this work was the development of a reliable technique to evaluate the intensity of acoustic cavitation during degassing of aluminium melts and to use it to select the optimum processing time for an envisaged degassing efficiency.A high sensitivity piezoelectric disk type device was used as a sensing feedback in water and liquid AlSi9Cu3 alloy. The signal acquisition and processing was carried out on a dedicated LabVIEW® based application which allowed real-time monitoring of the piezoelectric sensor's data and ultrasonic parameters. Standard Fast Fourier Transform was applied to obtain the dominant frequencies, as well as the sub and ultra-harmonics. It was found that the amplitude of the FFT sub-harmonic (f/2) was the best indicator to evaluate the process degassing efficiency, and it could be used to select the optimal processing time, independently of other variables.The developed methodology was applied to several AlSi9Cu3 melts, and validated by measuring the final alloy densities and the volume fraction of porosities, revealing that it is an efficient, fast and cost effective technique to evaluate the degassing treatment of aluminium alloys. Experimental curves of AlSi9Cu3 alloy degassing efficiency as a function of f/2 amplitude are presented for different degassing times.

Touch Sensitive Impact Controlled Electronic Signal Transfer Device

One embodiment of the Touch sensitive impact controlled signal transfer device invention whereas the invention is used as a musical glove device that sends electrical signals to a sound module when areas of the glove containing piezoelectric discs are tapped or otherwise impacted on a surface and where the force applied by impact to the piezoelectric disc or discs is interpreted by the sound module and said module produces a sound at a volume level directly related to the force of impact on the piezoelectric discs and where multiple piezoelectric disks are located in each glove allowing a plurality of sounds by tapping different areas of the glove, such as the palm, thumb and fingers.

Monodisperse hydrogel microspheres by forced droplet formation in aqueous two-phase systems

This paper presents a method to form micron-sized droplets in an aqueous two-phase system (ATPS) and to subsequently polymerize the droplets to produce hydrogel beads. Owing to the low interfacial tension in ATPS, droplets do not easily form spontaneously. We enforce the formation of drops by perturbing an otherwise stable jet that forms at the junction where the two aqueous streams meet. This is done by actuating a piezo-electric bending disc integrated in our device. The influence of forcing amplitude and frequency on jet breakup is described and related to the size of monodisperse droplets with a diameter in the range between 30 and 60 μm. Rapid on-chip polymerization of derivatized dextran inside the droplets created monodisperse hydrogel particles. This work shows how droplet-based microfluidics can be used in all-aqueous, surfactant-free, organic-solvent-free biocompatible two-phase environment.

Monopole Acoustic Transmitter Comprising A Plurality Of Piezoelectric Discs

A monopole acoustic transmitter with at least one disc assembly with a plurality of piezoelectric discs configured to optimized acoustic pressure output within a desired frequency range while meeting physical restrictions of LWD and MWD logging systems. The transmitter is disposed in a recess or “slot” in the perimeter of a logging tool housing to reduce acoustic pressure waves transmitted directly along the tool housing and to optimize acoustic energy transmission into the borehole environs. In order to increase acoustic pressure output at a desired logging frequency range, the plurality of piezoelectric discs in each of at least one disc assembly are connected electrically in parallel and fired simultaneously. The polarity of the discs and the wiring arrangement are such that each disc expands or contracts in a common direction during simultaneous firing by an applied voltage. The desired output frequency is obtained by selectively polarizing and dimensioning the discs within the one or more disc assemblies. Each disc assembly is preferably disposed within an oil filled pressure housing that is pressure and temperature compensated. The axis of the at least one disc assembly can be parallel or perpendicular to the major axis of the logging tool.

Nondestructive Evaluation of Early Stage Plasticity and Fatigue Damage of Aluminum Alloy Using Nonlinear Ultrasonic Method

Early stage of plasticity and fatigue damage are difficult to detect by using conventional ultrasonic techniques.Nonlinear ultrasonic technique based on harmonic generation has been shown to have the ability to solve the question.A nonlinear ultrasonic high power transmission testing system is developed to detect early-stage plasticity and fatigue damage of Aluminum 2024-T4 alloy.During the test,the nonlinear parameter of the material based on the amplitude of second harmonic is monotonically correlated with the plasticity and fatigue damage of the samples.The experimental nonlinearities are successfully reduced by using the natural filter effect of piezo-electric discs,which makes the experimental method more robust.The experimental results show that the nonlinear ultrasonic technique based on harmonic generation can be used to detect early-stage plasticity and fatigue damage of aluminum alloy.

Mixing enhancement for high viscous fluids in a microfluidic chamber

Due to small channel dimensions and laminar flows, mixing in microfluidic systems is always a challenging task, especially for high viscous fluids. Here we report a method of enhancing microfluidic mixing for high viscous fluids using acoustically induced bubbles. The bubbles can be generated in an acoustically profiled microfluidic structure by using a piezoelectric disk activated at a working frequency range between 1.5 kHz and 2 kHz. The mixing enhancement is achieved through interactions between the oscillating bubbles and fluids. Both experimental studies and numerical simulations are conducted. In the experiments, DI water-glycerol mixture solutions with various viscosities were used. The results, based on the mixing efficiency calculated from experimentally acquired fluorescent images, showed that good mixing can occur in the DI water-glycerol solutions with their maximum viscosity up to 44.75 mPa s, which to our best knowledge is the highest viscosity of fluids in microfluidic mixing experiments. To explain the mechanisms of bubble generation, the numerical simulation results show that, corresponding to the actuations at the working frequency range used in the experiment, there exists a low pressure region where the pressure is lower than the water vapor pressure in the DI water-glycerol solutions, resulting in the generation of bubbles.

Optimization of a Microfluidic Mixing Process for Gene Expression–Based Bio-Dosimetry

ABSTRACT In recent decades advances in radiation imaging and radiation therapy have led to a dramatic increase in the number of people exposed to radiation. Consequently, there is a clear need for personalized biodosimetry diagnostics in order to monitor the dose of radiation received and adapt it to each patient depending on their sensitivity to radiation exposure (Hall and Brenner 2008). Similarly, after a large-scale radiological event such as a dirty bomb attack, there will be a major need to assess, within a few days, the radiation doses received by tens of thousands of individuals. Current high-throughput devices can handle only a few hundred individuals per day. Hence, there is a great need for a very fast, self-contained, noninvasive biodosimetric device based on a rapid blood test. This article presents a case study where regression methods and designed experiments are used to arrive at the optimal settings for various factors that impact the kinetics in a biodosimetric device. We use ridge regression to initially identify a set of potentially important variables in the mixing process, which is one of the critical subsystems of the device. This was followed by a series of designed experiments to arrive at the optimal setting of the significant microfluidic cartridge and piezoelectric disk (PZT; Sadler and Zenhausern 2006; Lee et al. 2005) related factors. This statistical approach has been utilized to study the microfluidic mixing to mix water and dye mixtures of 70 μL volume. The outcome of the statistical design, experimentation, and analysis was then exploited for optimizing the design, fabrication, and assembly of microfluidic devices. As a result of the experiments performed, the system was fine-tuned and the mixing time was reduced from 5.5 to 2 minutes.

Characterization of a Piezoelectric Buzzer Using a Michelson Interferometer

A piezoelectric material generates an electric potential across its surface when subjected to mechanical stress;1 conversely, the inverse piezoelectric effect describes the expansion or contraction of the material when subjected to some applied voltage. Piezoelectric materials are used in devices such as doorbell buzzers, barbeque igniters, and also as the scanning and approach mechanisms in scanning probing microscopy. The assembly of a scanning tunnelling microscope (STM)2 at Thompson Rivers University has motivated a characterization of the sensitivity and hysteresis3 of piezoelectric discs using a Michelson interferometer. The investigation uses an interferometer4 and a simple photodiode circuit to track the fringes. As a possible undergraduate lab, the measurement provides an introduction to piezoelectric materials (including hysteresis), the Michelson interferometer, and data acquisition techniques.

Magnetic field sensing with a single piezoelectric ceramic disk: Experiments and modeling

This study reports on the magnetoelectric coupling in a single piezoelectric ceramic disk subjected to both ac and dc magnetic fields perpendicularly applied to the sample’s plane. Eddy currents are induced within the electrodes of the ceramic by ac magnetic flux via the Lenz–Faraday equation and yields Lorentz forces and stresses which are transferred to the piezoelectric ceramic. This latter transduces stress into electrical charges through electromechanical coupling in radial mode. The measured output magnetoelectric current could be successfully modeled using piezoelectric equations providing the inductively coupled voltage between the electrodes of the ceramic is taken into account. This voltage originates from the ac magnetic flux through the experimental loop, which is not a perfect short-circuit and yields two other contributions to the total current: piezoelectric current due to the induced electric field and the dielectric loop current. Radial velocity measurements confirmed the distinct contributions to the current. Thus, room temperature magnetic field detection is achievable using this single piezoelectric disk with a good sensitivity and linear response versus dc magnetic field change.

Preparation of Glass-Coated Cu Electrodes and their Effect on Piezoelectric Device

In this study, a technique to prepare metal powder coated by glass was examined. Specifically, the glass-coating on Cu and its oxidation resistance were investigated. The Cu powder was coated with borosilicate glass via the sol-gel process. Nominal weight ratios of Glass/Cu were controlled to be 2%, 5%, 10% and 20%. The average particle sizes of the as-received and coated Cu powders were 0.59 μm and 0.63∼0.67 μm, respectively. The pastes consisting of coated powder and other conventional organic vehicle were fabricated. The coated Cu paste could be burnt-out at 500°C under air atmosphere, and was then sintered at 1050°C under N2 atmosphere. Using the glass-coated Cu paste and a 0.945(Bi0 . 5Na0 . 5)TiO3–0.055BaTiO3 (BNT-BT) piezoelectric ceramic, the piezoelectric devices were fabricated. Their performances were investigated in comparison with piezoelectric disk devices using BNT-BT base ceramic and Ag electrode.

A simple apparatus for the injection of lithium aerosol into the scrape-off layer of fusion research devices

A simple device has been developed to deposit elemental lithium onto plasma facing components in the National Spherical Torus Experiment. Deposition is accomplished by dropping lithium powder into the plasma column. Once introduced, lithium particles quickly become entrained in scrape-off layer flow as an evaporating aerosol. Particles are delivered through a small central aperture in a computer-controlled resonating piezoelectric disk on which the powder is supported. The device has been used to deposit lithium both during discharges as well as prior to plasma breakdown. Clear improvements to plasma performance have been demonstrated. The use of this apparatus provides flexibility in the amount and timing of lithium deposition and, therefore, may benefit future fusion research devices.

Modal analysis and harmonic response of resonators: An extension of a mapped orthogonal functions technique

A mapped orthogonal functions technique is extended for solving three-dimensional acoustical wave problems with taking into account electrical sources. For validation and illustration purposes, it is applied to the determination of the frequency spectrum of a piezoelectric disc resonator. Formulation is given for the calculation of the electric input admittance along with specializations for open- and short-circuit boundary conditions. In view of validation, normal frequencies and electric input admittance are obtained for specific geometries where a one-dimensional analytical model is working and compared against results from the analytical approach. Illustrative results, dispersion curves for a PZT5A resonator and electromechanical coupling coefficients as a function of the diameter to thickness ratio for the first radial mode of a respectively PZT5A, AlN and SiC resonator are also given.

Field velocity resistivity probe for estimating stiffness and void ratio

Elastic and electromagnetic waves are commonly used to investigate various soil characteristics. The goal of this study is to estimate the elastic moduli and the void ratio based on both the compressional and shear wave velocities, and the electrical resistivity measured by field velocity resistivity probe (FVRP). The compressional and shear waves are measured by piezoelectric disk elements and bender elements installed at the end of the FVRP frame tip. The electrical resistivity is determined by the electrical resistivity probe installed at the tip of the FVRP frame. The FVRP tests are carried out in a clay–sand mixture prepared in a calibration chamber and in silty sand to silty clay soils in the field. The elastic waves and electrical resistivity are measured at every 1 cm. The field tests are carried out at a depth of 6–20 m, at 10 cm intervals, at the Southern coastal area of the Korean peninsula. The measured data are converted into the constraint and shear moduli based on the elastic waves. Void ratios are evaluated based on the elastic wave velocities and the electrical resistivity, and these void ratios match the volumetric void ratio well. This study suggests that the FVRP may effectively determine the elastic moduli and void ratio.

Substrate Integrated Evanescent-Mode Cavity Filter With a 3.5 to 1 Tuning Ratio

In this letter, the design and RF packaging of substrate integrated widely tunable filter is presented. The filter consists of two heavily loaded evanescent-mode cavities embedded into the substrate. The filter is actuated using two piezoelectric discs, which move thin, flexible membranes that form the top of the cavities. To demonstrate the wide tuning a filter is fabricated and measured to cover a very wide frequency range from 0.98 to 3.48 GHz (tuning ratio-3.55:1). The measured insertion loss is less than 3.57 dB for a 1.1% fractional bandwidth filter.