Piezoelectric Mode Research Articles

Real-time monitoring of adhesion and aggregation of platelets using thickness shear mode (TSM) sensor

Hemostasis is required to maintain vascular system integrity, but thrombosis, formation of a clot in a blood vessel, is one of the largest causes of morbidity and mortality in the industrialized world. Novel clinical and research tools for characterizing the hemostatic system are of continued interest, and the object of this research is to test the hypothesis that clinically relevant platelet function can be monitored using an electromechanical sensor. A piezoelectric thickness shear mode (TSM) biosensor coated with collagen-I fibers to promote platelet activation and adhesion was developed and tested for sensitivity to detect these primary events. Magnitude and frequency response of the sensor were monitored under static conditions at 37 °C, using platelet-rich plasma (PRP), and PRP with adenosine diphosphate (ADP), a clinical aggregation inhibitor (abciximab), or a collagen binding inhibitor. Sensors loaded with PRP exhibited a 3-stage response; no significant change in response for the first 20 min (Stage-1), followed by a larger drop in response (Stage-2) and subsequently, response gradually increased (Stage-3). Exogenous ADP stimulated an immediate Stage-2 response, while abciximab delayed and reduced the magnitude change of Stage-2. In the presence of collagen inhibitor, Stage-2 response was similar to that of control but was delayed by an additional 20 min. The obtained results, supported by epifluorescence and complementary SEM studies, demonstrated the selective sensitivity of TSM electromechanical biosensors to monitor platelet function and inhibition, particularly aggregation.

Na<sub>1-x</sub>K<sub>x</sub>NbO<sub>3</sub> (x=0.2~0.8) Lead-Free Piezoelectric Ceramics Prepared by Spark Plasma Sintering

Highly dense Na1-xKxNbO3 (x=0.2~0.8) ceramics were successfully prepared using spark plasma sintering (SPS) at temperature as low as 920°C. Solid solutions were formed during the composition range investigated. The piezoelectric constant and planar mode electromechanical coupling coefficient are significantly dependent on the Na/K ratio, with the maximum value of 148 pC/N and 38.9% at the composition Na0.5K0.5NbO3.

구조물 손상 탐지를 위한 경 방향 모드 압전 오실레이터 센서 개발

본 논문에서는 사회기반시설의 손상탐지를 위한 경 방향모드 압전 오실레이터의 가능성을 연구하였다. 경 방향 모드 오실레이터 센서는 구조물의 주요부에 부착된 경 방향 모드 압전소자와 피드백 오실레이터 회로로 구성되어있다. 구조물의 손상은 구조물의 임피던스를 변화를 야기 시키며, 그 결과로 구조물의 공진 주파수가 변화하게 된다. 오실레이터 센서는 간단한 방법으로 이 공진 주파수 변화를 연속적으로 관측할 수 있다. 본 연구에서는 알루미늄 시편에 크랙의 크기와 개수를 인위적으로 변화 시키면서, FEM해석과 실험을 통해 경 방향 모드 압전 오실레이터 센서의 적용 가능성을 증명 하였다. This paper presents the feasibility of a lateral mode piezoelectric oscillator to detect damages in civil infrastructures. The lateral mode oscillator sensor is composed of an electronic feedback oscillator circuit and a piezoelectric lateral mode vibrator to be attached to a structure of interest. Damage to the structure causes a change in the impedance spectrum of the structure, which results in a corresponding change of a resonant frequency of the structure. The oscillator sensors can instantly detect the frequency change in a very simple manner. Feasibility of the piezoelectric oscillator sensor was verified in this work with a sample aluminum plate where artificial cracks of different lengths and number were imposed in sequence. Validity of the measurement was confirmed through comparison of the experimental data with the results of finite element analyses of a plate with cracks.

Analysis of driving mechanism for tiny piezoelectric linear motor

Recently, a tiny piezoelectric linear motor using a vibration mode of the transducer has been invented. The motor consists of a shaft, mobile element, and piezoelectric transducer using a piezoelectric radial mode bimorph disk. The fringe of the bimorph disk is fixed firmly which means this area has no degree of freedom. Therefore, the radial mode of the transducer transfers to the flexure mode. The mobile elements move along the Pyrex shaft by the impact force generated by the flexure mode of the piezoelectric transducer. The motors are operated at their resonant frequencies. The dynamic properties of the motor have been intensively measured and analyzed according to the applied voltage waveforms at the resonant frequencies. As the sawtooth and rectangular voltage waveforms are applied, the velocity, the thrust force, and the velocity dependence of the mobile position are measured. The dynamic characteristics are also analyzed within a period of each wave using laser vibrometer. The velocity of the mobile is moderately constant along the shaft. The better dynamic characteristics are obtained in the case of applying the rectangular waveform.

Modeling of the influence of a prestress gradient on guided wave propagation in piezoelectric structures

The objective of this study is to model the propagation of guided waves in piezoelectric structures subjected to a prestress gradient. The constitutive equations for a piezoelectric bulk material are first modified to take into account a uniform prestress on a given cross section. Then, these modified constitutive equations are used to derive a formalism for the propagation of guided waves in piezoelectric structures under a prestress gradient. In particular, we modify the recursive stiffness matrix method to introduce a gradient of stress in a piezoelectric structure. Numerical studies are then led for a bending and for an exponential stress profile. For a piezoelectric plate, the Lamb and shear horizontal modes are found to be sensitive to the prestress gradient. In particular, some key features of dispersion curves appearing in the presence of a gradient of properties are highlighted. In the last part, these results are extended to a piezoelectric film laid down on a substrate in order to model the importance of the stress gradient on the behavior of an integrated structure. Lithium niobate is used for the plate and film material, and a silicon crystal is used as the substrate.

Flexible ferroelectret field-effect transistor for large-area sensor skins and microphones

Ferroelectrets generate an electric field large enough to modulate the conductance of the source-drain channel of a thin-film field-effect transistor. Integrating a ferroelectret with a thin-film transistor produces a ferroelectret field-effect transistor. The authors made such transistors by laminating cellular polypropylene films and amorphous silicon thin-film transistors on polyimide substrates. They show that these ferrroelectret field-effect transistors respond in a static capacitive or dynamic piezoelectric mode. A touch sensor, a pressure-activated switch, and a microphone are demonstrated. The structure can be scaled up to large-area flexible transducer arrays, such as roll-up steerable compliant sensor skin.

Piezoelectric Al<tex>$_0.3$</tex>Ga<tex>$_0.7$</tex>As Longitudinal Mode Bar Resonators

This paper reports the modeling, fabrication, and experimental characterization of piezoelectric longitudinal mode bar resonators based on thin film single crystal Al/sub 0.3/Ga/sub 0.7/ As. Fabricated resonators with lengths ranging from 1000 /spl mu/m to 100 /spl mu/m have been characterized for operation in their first five odd longitudinal modes. Resonance frequencies range from 2.5 to 75 MHz, with quality factors up to 25 390 at 21.8 MHz in vacuum. Power handling capacity as high as -2.6 dBm is demonstrated at 18.8 MHz. Motional resistance and temperature stability of the resonators are also evaluated.

The study of an interaction of solid particles with various surfaces using TSM sensors

The interaction of solid particles with various surfaces has been experiencing growing interest in many areas of nanotechnology, colloidal science, and biology. In this paper the interactions of solid particles with the surface of piezoelectric thickness shear mode (TSM) sensors have been studied. A mechanical model has been presented to evaluate the effect of particle loading on the behavior of a TSM sensor. The main sources contributing to the interaction, such as Van der Waals force, friction force, and electrostatic force, are discussed. Experiments have been designed for 10-100 microm particles on the 5-MHz and 10-MHz TSM sensors. It has been shown that the resonant frequencies of the TSM sensors might increase or decrease depending on the interaction conditions. The results have shown that the TSM sensor technique could provide the information on the mass/size of a particle and the binding energy between a particle and the sensor surface. This technique may find its applications in characterizing the properties of an interaction between particles and various surfaces.

Piezoelectric resonance of lead zirconate titanate ceramics excited by a stepwise electric field

Transient current of ferroelectric ceramics has been intensively studied using a stepwise electric field. Abnormal oscillations were observed in the transient current when a stepwise electric field was applied onto modified lead zirconate titanate (PZT) ceramic samples in a very short time (less than 100ns) in the present study. Compared to the frequency spectrum of those samples, it is found that those frequencies of oscillations correspond to that of piezoelectric resonance. Four samples of PZT ceramics were cut into different dimensions according to the requirement of five different electromechanical coupling modes. Experimental results demonstrate that those five piezoelectric resonance modes of the ferroelectric samples could be excited by a stepwise electric field, and different resonance modes of a sample could be excited simultaneously. The authors also found that whether piezoelectric resonance could be excited depends on the parameters of test circuit.

EPITAXIALLY GROWN PbZr0.3Ti0.7O3 THIN FILMS ON LaMnO3 APPLICABLE TO NANO-STORAGE MEDIA

ABSTRACT We have investigated structural and electrical properties of PbZr0.3Ti0.7O3 (PZT) thin films deposited by pulsed laser deposition methods. PZT thin films have been deposited on LaMnO3 (LMO) bottom electrodes with LaAlO3 substrates during different deposition times. High-resolution x-ray diffraction data have shown that all the PZT films and bottom electrodes are highly oriented with their c-axes normal to the substrates. The thickness of each film is determined by field-emission scanning electron microscope. We have also observed root mean square roughness of 1 to 10 Å by using atomic force microscopy mode, and local polarization distribution and retention behavior of a ferroelectric domains by using piezoelectric force microscopy mode. A PZT/LMO structure has shown good ferroelectric and retention properties as a media for the nano-storage devices.

An adaptive mutation breeder algorithm for determining equivalent circuit parameters of a liquid-filled piezoelectric cylinder

Many acoustic systems require an equivalent electromechanical model to describe their behavior. As a result, a variety of models has been described in the literature including that of Mason, KLM, and Redwood. Although these models can describe complex acoustic systems, it is often difficult to extract circuit parameters for such systems using traditional theory. Aspects of mode superposition and frequency pulling between modes cause traditional theory to become increasingly complex in predicting equivalent circuit values. As a solution to this, an adaptive breeder algorithm is utilized as a means of predicting multiple resonance modes interacting with one another. A liquid-filled piezoelectric cylinder is used as an acoustic system to represent coupled piezoelectric and liquid vibrational modes. Using a variation of Mason’s transmission line model, an adaptive mutation breeder algorithm is used to predict the spectral response measured by an impedance analyzer. The acoustic model is shown to fit almost identically over the measured data for a variety of different-sized cylinders and liquids. It is further shown that the breeder algorithms may be used to predict the sound velocity and density of the liquid inside the cylinder.

Characterization of Piezoelectric Shear Mode Inkjet Actuator

ABSTRACTImpedance analysis was used to characterize the properties of Piezoelectric Shear Mode Inkjet Actuators. Ceramic actuators poled parallel to the channel walls exhibit good performance. Applying high voltage the actuators can be depolarized at high temperature or even re-poled perpendicular to the channel walls. This limits the drive pulse and the bias voltage below the coercive voltage. The leakage current also has been studied with various conditions. For the ferroelectric ceramic materials, the Schottky barrier also can be measured at definite voltage and temperature ranges, the corresponding Barrier for the Al/PZT contact is 0.98 eV. A pronounced low-temperature dielectric relaxation process was observed between 100–150 K; the relaxation rate fellows the Arrhenius law, the fitted activation energy is 0.194 eV. The resonance frequency increases as decreasing the temperature because of increasing for the stiffness coefficient at low temperature.

Planar coil excitation of multifrequency shear wave transducers

A transducer format that replaces the electrode of an acoustic resonator with a planar spiral coil is used to extract multifrequency spectral information from adsorbed protein films. Both amorphous silica and crystalline piezoelectric resonators are driven to resonance by forces induced across an air gap by magnetic direct generation and piezoelectric excitation induced by the electromagnetic field of the coil. Inspection of the harmonic frequencies between 6 MHz and 0.6 GHz indicates that the response of these two resonator types is described by different families of shear acoustic standing waves, with similar acoustic features to the quartz crystal microbalance. Exposure of the devices to protein solutions results in reproducible shifts of their harmonic frequencies, up to a maximum of 15 kHz and increasing linearly with frequency and operating mode. The gradient, determined from the ratio of the frequency change to the operating frequency was determined as 21.5 × 10 −6 for the quartz device and 60.9 × 10 −6 for the silica device. Consistency with the Sauerbrey equation for the piezoelectric linear shear mode was comparable at a predicted value of 22.5 × 10 −6, but not for the radial shear mode of the silica device at 12.7 × 10 −6. Opportunities resulting from the wide bandwidth of the planar coil excitation and choice of acoustic mode are discussed with respect to acoustic fingerprinting of adsorbed proteins.

Modelling of a microfluidic device with piezoelectric actuators

This paper presents the modelling of a given microfluidic device, that is applied as a drop-on-demand printhead for different printing tasks. Piezoelectric bend mode actuators are used to eject a droplet from the respective nozzle on demand. The device is considered as a coupled system consisting of an electric, a mechanical and a fluidic part. The electric and mechanical parts of the piezoelectric actuator are described by conventional lumped elements, while the complex three-dimensional fluid analysis is performed by a commercial computational fluid dynamics (CFD) free-surface modelling package. The model helps one to understand the fluid dynamics and thus to study different design and operating parameter aspects. The general approach to the problem of modelling a microfluidic device as presented here can also be applied in various other modelling tasks.

Radial Mode Piezoelectric Response of La Modified Lead Zirconate Titanate in Morphotropic Phase Boundary Region

Room temperature radial mode piezoelectric response of Lanthanum modified Lead Zirconate Titanate (Pb(Zr0.57Ti0.43)O3+X at%La) (PLZT) is characterized by Vector Impedance Spectroscopy. Piezoelectric parameters (electromechanical constants KP, K31, elastic compliance sE11, strain constants d31, dh, voltage constant g31and planar piezoelectric constants radial mode coupling constant kp, piezoelectric constant ep31and mechanical constant cp11) have been determined for La doping ranging from 3 to 12 at%. Piezoelectric parameters KP, kp, d33and d31peak at 5–6 at%of La while dielectric constants˜T33,˜P33and piezoelectric constant ep31peak at 8 at%. An average value of Poisson's ratioσEis found to be 0.34±0.01. The conductivity of PLZTs follows the universal behavior.

Domain Structure, Local Hysteresis and Ferroelectric Phase Transition in (CH3NH3)5Bi2Br11 (MAPBBB) Single Crystals

Local ferroelectric properties of single crystals (CH3NH3)5Bi2Br11 (MAPBB) are investigated by Scanning Probe Microscopy (SPM) in a piezoelectric contact mode. The SPM signal proportional to the effective piezoelectric coefficient, deff, is measured along with the standard topography. Both ferroelectric domain imaging and local hysteresis measurements are performed at room temperature in the close vicinity of the phase transition temperature (Tc ≈ 39°C). Lamellar domain structure with the phase contrast due to 180° domains is observed for the surfaces perpendicular to the polar direction. Local hysteresis loops acquired by SPM are well saturated with the average coercive voltage of ∼15 V. The shape of the loops is found to depend on the stiffness of the SPM cantilever. Local studies are complemented with the macroscopic measurements (polarization, piezoelectric coefficient, dielectric permittivity) performed in the temperature range including Tc (20–39°C). The mechanisms of the domain contrast and prospects of using MAPBB for high-density data storage are discussed.

Dielectric Characteristics of In-Plane Polarized Lead Zirconate Titanate Thin Films on Oxide Layers

Sol-gel derived lead zirconate titanate (PZT) films have been prepared on STO-passivated silicon substrates. The STO buffer layer of thickness about 55 nm is prepared by rf-magnetron sputtering. XRD results reveal that the PZT film has well-crystallized perovskite phase, indicating that the thin STO layer can effectively prevent reaction and inter-diffusion between the PZT film and silicon substrate. Interdigitated electrodes (IDEs) have then been deposited on the PZT film by magnetron sputtering and patterned using the standard photolithography. With the IDEs, the dielectric and ferroelectric properties of the PZT film under transverse or in-plane electric fields have been investigated. By assuming a uniform distribution of electric field (in-plane electric field model), the estimated relative permittivity of the PZT film is about 2100, while the dielectric loss is less than 1%. Good in-plane polarization hysteresis loop is observed, showing an observed remanent polarization value of 21 μC/cm2, which is comparable to that of a PZT film with both top and bottom electrodes. The in-plane polarized PZT/STO/SiO2/Si film can be used to fabricate d33-mode unimorph bending transducers, which will have much better performance than the conventional bending transducers driven electromechanically through the piezoelectric d31 mode.

Stress-induced suppression of piezoelectric properties in PbTiO3:La thin films via scanning force microscopy

Sol-gel derived polycrystalline La-doped PbTiO3 films are investigated by scanning force microscopy (SFM) in a piezoelectric contact mode. The SFM signal proportional to the effective piezoelectric coefficient, deff, is measured inside individual domains as a function of the mechanical force exerted by the SFM tip on the film’s surface. It is found that the piezoelectric signal can be fully suppressed under sufficiently high force (∼20–22 μN). The suppression is qualitatively different for domains of opposite polarities where deff may change its sign depending on the orientation of polarization vector. The piezoelectric hysteresis loops acquired under increasing force gradually shrink with an asymmetric decrease of the piezoelectric coefficients. This leads to a pronounced vertical shift of the loops (deff offset). The obtained results are discussed in terms of the competing electrostatic and piezoelectric contributions to the measured signal and stress-induced polarization instabilities in the vicinity of the SFM tip.

Modeling and Numerical Simulation of the Crosstalk Behavior of a DOD Printhead

This paper reports the modeling of a given printhead with piezoelectric bend mode actuators. The model describes the electric, mechanical as well as the fluid dynamic characteristics of the printhead. The electric and mechanical parts of the piezoelectric bend mode actuator are described by conventional lumped elements which interact as constituent parts of a Kirchhoffian network. The complex three-dimensional fluid analysis is performed by a commercial computational fluid dynamics (CFD) free-surface modeling package. The fluid structure coupling is realized by exchanging of data between the electro-mechanical model and the fluid simulation tool for every numerical time step.The piezoelectric printhead has been computationally simulated to analyze the fluid flow dynamics and the jet forming process. Moreover inter-channel crosstalk caused by interconnected fluid channels of the printhead is studied. As a result, this paper discusses the fundamentals of the crosstalk problem and shows ways for crosstalk compensation methods based on optimized compensation drive pulses.

Piezoelectric shear mode drop-on-demand inkjet actuator

We report on comprehensive characterization of piezoelectric shear mode inkjet actuators micromachined into bulk Pb(Zr0.53Ti0.47)O3 (PZT) ceramics. The paper starts with an overview of different drop-on-demand inkjet systems, whereas the main attention is then turned on particular Xaar-type piezoelectric shear mode inkjet printheads. They are an example of complex microelectromechanical system (MEMS) and comprise a ferroelectric array of 128 active ink channels (75 μm wide and 360 μm deep). Detailed information about fabrication process and principles of operation are given. Since each actuating wall of 128 channels is a piezoelectric capacitor metallized from both sides to be animated by electric pulse, electrical properties of channel walls (CWs) are easy to test and serve as a fingerprint of actuator performance in the virgin state as well as after high voltage/elevated temperature heavy duties. We present several techniques to control manufacturing process and fatigue effects. So, continuous wave and pulsed spectroscopy and hysteresis P–E loop tracing showed that compared to a virgin PZT ceramics state, dielectric permittivity (ε′) was reduced three times, the loss factor (tan δ) increased from initial 4.8 to 6.6%, remnant polarization decreased by 43%, coercive field increased by 38%, whereas Curie temperature increased from 508 to 560 K after 90,000 cycles of ferroelectric hysteresis P–E loop tracing at 50 Hz at electric field of 88.5 kV/cm. Heat treatment also results in PZT ceramics degradation: appreciable reduction of the coupling coefficient (k15) and the degradation of inkjet performance were revealed by optical stroboscope technique: 8.7 and 14% reduction of drop velocity and volume in electrically fatigued actuator, 2.5% reduction of drop velocity and unchanged drop volume in temperature-treated actuators.