Piezoelectric Bimorph Actuator Research Articles

A material rigidity effect of a bimorph piezoelectric actuator

This paper presents the numerical modeling of a piezoelectric actuator used to avoid thelimitation of the lock-in region in a ring resonator. Ring resonators have proved suitable foruse as inertial sensors for navigation, guidance and attitude controls. However, theiraccuracy has been limited by the lock-in region due to frequency coupling between twocounter-propagating waves at low rotation rates. This coupling introduces no phasedifference, and no angular increment is detected. The problem can be overcome bymechanically dithering the ring resonator. Mechanically, the vibro-elastic bimorphpiezoelectric actuator has been used as a control but is influenced by piezoelectric rigidityeffects. To more accurately predict the dithering frequency of a mechanical dither,numerical modeling of a piezoelectric actuator includes the piezoelectric rigidity effect ofthe actuator, which occurs in both the static and dynamic behaviors of composite plateshaving piezoelectric layers symmetrically bonded to the top and bottom surfaces.Corrections were made to figures 1 and 2 on 13 June 2007. The corrected electronic version is identical to the print version

Frequency dependence of piezoelectric vibration velocity

Five piezoelectric series bimorph actuators with different lengths were measured to examine the effect of frequency on vibration velocity. It is found that the vibration velocity is frequency dependent. In low-frequency range, the mechanical and electrical losses are lower, and the actuator is able to achieve a higher vibration velocity approaching the mechanical limitation. On the contrary, in high-frequency range, the velocity is limited by heat generation from the mechanical and electrical losses. The velocity obtained is lower than that achieved from the low-frequency actuators. Heat generation increases with frequency, mechanical stress and applied electric field.

Study on the flow structure at the spanwise edge of spreading turbulent region and its control

The structure at a spanwise edge of spreading turbulent region is studied in a wind tunnel experiment using conditional-sampling and ensemble-averaging techniques. A turbulent region is created by locally tripping the laminar boundary layer using two bi-morph piezoelectric actuators. The turbulent region protrudes into the laminar region at the middle height of the boundary layer. The results show that when the turbulent region spreads, a pair of streamwise vortices exists near the interface on the turbulent side, and the flow induced by the vortex pair pushes the turbulent fluid into the laminar region. An experiment in which a thin flat plate is inserted into the boundary layer reveals that the spanwise spreading of the turbulent region can be effectively suppressed by destroying these vortical structures.

Resonant Polymeric Waveguide Cantilever Integrated for Optical Scanning

We present SU-8 as an optical waveguide and its integration into a functional one- and two-dimensional (1-D and 2-D) scanning device. The waveguide is fabricated as a tapered structure and cantilever beam (100times85times2100 mum). It is mounted onto a 2-D coupled bimorph piezoelectric actuator and driven at resonant frequencies of 4.71 kHz in the vertical and 25 Hz in the horizontal. This raster motion allows for 2-D image scanning when in combination with a light source and detector. An analysis of the polymer's optical capabilities has shown mode coupling efficiencies of 96% and measured a total power output intensity of 20% with a 633-nm light source. The output power can be attributed to the butt-end coupling misalignment, scattering losses due to surface roughness, and absorption. The total vertical tip displacement is 669 mum with an angle of 25 deg when driven with a 47-mum base excitation. A specific application for the design is in the area of endoscopy, where there is a need for a minimally invasive device that reduces the discomfort experienced by the patient. SU-8 as the functional waveguide is the initial phase in creating a microfabricated endoscope system

Development of a micro biochip integrated traveling wave micropumps and surface plasmon resonance imaging sensors

Since most of miniaturized surface plasmon resonance (SPR) sensing systems need commercially available peristaltic or syringe pumps, it is difficult to reduce the system size, biosample volume, and the production cost. In this paper, a compact biochip for clinical diagnosis is presented. The proposed biochip is integrated traveling wave micropumps and SPR imaging sensors on one chip. The micropump is composed of flexible microchannel and piezoelectric bimorph actuator array, and achieved the maximum flow rate 336 μl/min. The SPR imaging biosensor can quantitatively measure biosamples with multi microchannels, i.e. one biosample and two reference flows to obtain an analytical curve. The SPR imaging measurements with bovine serum albumin solutions were carried out using the prototype of the proposed diagnostic system composed of a pair of the micropump and the sensor. Since the clear SPR signal curve was observed, it was confirmed that the proposed system can be applicable to the clinical diagnosis.

圧覚・滑り覚同時呈示形触覚ディスプレイ用二軸アクチュエータ

According to the previous psychophysical experimental results, since human beings feel different sensations for pressure and shearing vibration applied to their finger surface, a new tactile display array consisting of multi-axial micro actuators is required to enhance degree of tactile virtual reality. In the present paper, we experimentally design serial and parallel typed two-axial micro actuators, which are utilized for the key part of the tactile display. The serial typed two-axial actuator comprises bimorph actuators connected in series. The parallel typed two-axial actuator is composed of two bimorph piezoelectric actuators and two small links connected by three joints. We formulate kinematics for the parallel typed two-axial actuator because the endpoint is controlled in the two-dimensional coordinate. We perform a series of experiments to evaluate these two-dimensional actuators. Although the serial typed actuator has different characteristics on x- and y-directional coordinates, it has an advantage on compactness. On the other hand, the parallel typed two-axial actuator has almost same characteristics on both x- and y- coordinates, and has wide strokes of about 1mm. Considering these characteristics depended upon actuator type, we will design the tactile display combined the serial and parallel typed two-axial actuator.

Proposal of A New Bimorph Piezoelectric Actuator for Blood Extraction Pump in Health Monitoring System

Health monitoring system equipped with blood extraction pump is one of the important problems for new medical technology to support the advanced age society. In this paper, a new piezoelectric actuator for blood extraction pump was proposed to increase volumetric change in pump. We devised the geometry of piezoelectric actuator with some slits that allows the stretching and contracting deformation in in-plane direction to create large deflection in out-of-plane direction. Focusing on a disc-type bimorph plate with some slits, the deformations under static electric load have been analyzed by finite element method with consideration of two geometric parameters, length l and width w of slits. The computational results indicated that the deformation of bimorph actuator changes from complex mode to single mode according to increase of slit length, and that single mode presents remarkable increase of deflection under surrounding-fixed condition. And then, a bimorph actuator with 4 slits l = 2.0, w = 0.5mm has been manufactured as an experiment. As a result, a developed actuator was proved to increase the deflection under dynamic electric load compared with a conventional bimorph actuator without slits.

Electrical Characteristics of Piezoelectric RF-MEMS Tunable Capacitor

Piezoelectric RF-MEMS tunable capacitors are useful components for realizing reconfigurable RF circuits for multi-band mobile terminals. In this paper, we describe fabrication process of an AlN RF-MEMS tunable capacitor and electrical characteristics of the tunable capacitor. We chose AlN as piezoelectric material and Al as electrode material, because these materials are compatible with conventional CMOS processes. The tunable capacitor utilized the piezoelectric bimorph actuator with folded beam structure. The structure of the actuator can cancel curling of the beam due to residual stress of the AlN piezoelectric actuator. After subtraction of parasitic components, net capacitance of the tunable capacitor changed from 0.20pF to 0.51pF with drive voltage ranging from 0V to 8V. The tuning ratio was 2.6. Q factor of the capacitor varied 29 to 11 at the same voltage range.

Polyimide amplified piezoelectric scanning mirror for spectral domain optical coherence tomography

The authors present polyimide amplified piezoelectric bimorph scanning mirrors for application in optical coherence tomography (oct). These devices use piezoelectric bimorph actuators to drive microfabricated polyimide structures at resonance. These devices have tilting tables (either 1.125 or 2.25mm wide) that tilt on 3μm thick torsion hinges to amplify the motion of the bimorph actuators and produce large scan ranges. These devices have been integrated into the scanning arm of a spectral domain OCT imaging system. Preliminary in vivo images have been obtained with scans of 40°–50° at real-time imaging rates of 25–41frames∕s.

RF-MEMS Tunable Capacitor With 3 V Operation Using Folded Beam Piezoelectric Bimorph Actuator

Tunable capacitors with high tuning range and high Q-factors are indispensable for realizing reconfigurable radio-frequency (RF) circuits for multiband/multimode next-generation mobile wireless communication terminals. A novel RF microelectromechanical systems tunable capacitor having a piezoelectric bimorph actuator has been developed using a complementary metal-oxide-semiconductor compatible surface micromachining process. Folded beam piezoelectric actuators were introduced to cancel curling of the actuator beam due to residual stress. The continuous wide tuning ratio of three was realized at an operation voltage of less than 3 V for the first time

Symbolic realization of asymptotic time-scale and eigenstructure assignment design method in multivariable control

This paper reports on a symbolic realization of the asymptotic time-scale and eigenstructure assignment (ATEA) state feedback design technique for multivariable control. The resulting state feedback laws are parameterized in a scalar ε. Under these state feedback laws, the closed-loop system possesses a pre-specified time-scale and its eigenstructure approaches a pre-specified one, as the value of the parameter ε approaches zero. By appropriately specifying the time-scale and the eigenstructure, the feedback laws can be obtained to solve various control problems, such as the H 2 and H ∞ suboptimal control, and almost disturbance decoupling problems. We present, in this paper, the software implementation of the ATEA design algorithm using the MATLAB symbolic programming technique. Our m-functions are capable of returning a result, which is explicitly expressed in terms of a symbolic variable epsilon, which represents ε. The controller design for a piezoelectric bimorph actuator is used to illustrate how the symbolic realization works.

Electric energy generator

This study reports an extremely cost-effective mechanism for converting wind energy into electric energy using piezoelectric bimorph actuators at small scale. The total dimensions of the electric energy generator are 5.08 x 11.6 x 7.7 cm3. The rectangular, box-shaped body of the overall structure is made using 3.2-mm thick plastic. Slits are made on two opposite faces of the box so that two columns and six rows of bimorph actuators can be inserted. Each row of bimorph actuators is separated from each other by a gap of 6 mm, and the two columns of bimorphs are separated from each other by a gap of 6.35 mm. In between the two columns, a cylindrical rod is inserted consisting of six rectangular hooks. The hooks are positioned in such a way that each of them just touches the two bimorphs on either side in a particular row. As the wind flows across the generator, it creates a rotary motion on the attached fan that is converted into vertical motion of the cylindrical rod using the cam-shaft mechanism. This vertical motion of the cylindrical rod creates oscillating stress on the bimorphs due to attached hooks. The bimorphs produce output voltage proportional to the applied oscillating stress through piezoelectric effect. The prototype fabricated in this study was found to generate 1.2 mW power at a wind speed of 12 mph across the load of 1.7 komega.

2306 2軸ピエゾアクチュエータの開発に関する研究(OS8-2 アクチュエータシステム(2))

We are studying a two-axis micro-actuator to enhance the presentation reality of a tactile display that is capable of presenting pressure distribution and shearing force. The actuator is composed of sequentially connected x- and y-directional actuators ; each actuator is comprised of bimorph piezoelectric actuators. The x- and y-directional actuators are independently controlled by changing the applied voltage to position a probe that is attached to the tip of a two-axial actuator. The maximum displacement and force generated by the x-directional actuator are 1.1mm and 0.03N, respectively. Those generated by y-directional actuator are 1.0mm and 0.06N, respectively. Since relationship between applied voltage and displacement caused by the voltage shows a hysteresis loop in the bimorph actuator used as components of the two-axis actuator, we produce a control system for the two-axial actuator based on a multi-layered artificial neural network to compensate the hysteresis.

Optimization of a piezoelectric bimorph grasper for use in minimally invasive surgical applications

The potential use of piezoelectric bimorph actuators in minimally invasive surgery suture-needle grasper/holder applications is explored computationally. Upon defining the design/functional requirements for such surgical tools, a finite element analysis of the underlying piezoelectric boundary value problem is combined with the genetic algorithm optimization routine to arrive at an optimal morphology of the suture-needle grasper/holder. The results obtained show that, if the actuator is based on several constant-thickness segments, a proper combination of thicknesses of such segments can substantially improve the performance of such surgical tools. Specifically, a good combination of the relatively large grasper-jaws opening and the required level of the holding force when the grasper is closed on a 0.5 mm diameter suture-needle is obtained. The effect of orientation of the poling direction in the piezoelectric layers on the performance of the bimorph actuator is also examined. It is found that, at the same level of the required grasping force, a change in the poling direction by about 2.3° from the through-the-thickness direction can increase the maximum grasper-jaws opening by about 10 per cent.

Resonant micro-mirror excited by a thin-film piezoelectric actuator for fast optical beam scanning

A silicon resonant torsional micro-mirror excited by piezoelectric bimorph actuators is presented. The bimorph actuators consist of a single-crystal silicon flexible beam or membrane and a PZT thin film. The mechanical elements are etched in the 20 μm thick superficial layer of a SOI substrate, thereby ensuring the flatness of the 500 μm-diameter gold-coated mirror. This device achieves optical beam scanning with large angular deflection at high frequency. In air, we have measured scanning up to 19.8° at 1.8 kHz, 99.1° at 10.6 kHz and 40.8° at 25.4 kHz. The applied driving voltage is sinusoidal with an amplitude under 42 V PP and with a 6 V DC bias voltage. At large oscillation amplitude, a non-linear hard-spring effect has been observed. In vacuum, a 78° optical scanning has been obtained with less than 1 V PP.

Mechanical Tuning of Superconducting Lumped Element Filter

The tunable filter has variable center frequency (f/sub 0/) and variable bandwidth (BW) that can be adapted to software defined radio. In our mechanical tunable filter, capacitance of each element is changed by motion of dielectric plate that is located above the capacitive elements. The dielectric plates are moved by piezoelectric bimorph actuators. Tuning test of the f/sub 0/ in a cryocooler is performed using an actual superconducting filter fabricated with YBa/sub 2/Cu/sub 3/O/sub y/ thin film deposited on an MgO (100) substrate. Taking into account of the effective change of parallel capacitance to ground plane by movement of dielectric plates above the element, we choose the coplanar wave guide type filter that has the ground plane on top side of the substrate. Suitable design of the mechanically tunable superconducting lumped element filter is discussed.

Layerwise Laminate Analysis of Functionally Graded Piezoelectric Bimorph Beams

A layerwise finite element formulation developed for piezoelectric materials is used to investigate the displacement and stress response of a functionally graded piezoelectric bimorph actuator. The formulation is based on the principles of linear thermopiezoelectricity and accounts for the coupled mechanical, electrical, and thermal responses of piezoelectric materials. The layerwise laminate theory is implemented into a linear beam element in order to provide a more accurate representation of the transverse and shear effects that are induced by the increased inhomogeneities introduced through-the-thickness by the functionally graded materials. The accuracy of the formulation is verified with previously published experimental results for a piezoelectric bimorph actuator. Additional studies are conducted to analyze the impact of electric and thermal loads on the deflections and stresses in a bimorph actuator. Results of the study help to demonstrate the capability of the layerwise theory to provide a more complete representation of the through-the-thickness effects that are no longer negligible even in thin piezoelectric beams. In addition, the effects of varying piezoelectric properties through-the-thickness of the beam are shown to provide additional benefits in minimizing the induced deformations and stresses.

A new type of parts feeder driven by bimorph piezo actuator

A novel meander-line structure implemented with bimorph piezoelectric actuators driven by two sets of alternating current power with phase difference is developed in this article. Via the generated traveling wave, this mechanism is able to transport parts. The dynamic modeling of the structure, the driving control circuitry design, the motion trajectory analysis and the optimal transport feed rate is studied, and also verified by the practical experiment.

Piezoelectric properties of lead-free CaBi4Ti4O15 thin films

Ca Bi 4 Ti 4 O 15 (CBTi144) thin films are evaluated for use as lead-free thin-film piezoelectrics in microelectromechanical systems. CBTi144 thin films were prepared on Pt substrates by dip coating a precursor solution of metal alkoxides. We fabricated a piezoelectric bimorph actuator using those films and analyzed the displacement induced by the electric field. Young’s modulus was measured by the vibrating-reed technique and the piezoelectric constant d31 was derived by analysis of bending displacement and measurement of displacement-voltage curve. The measurements revealed that the CBTi144 films had a large piezoelectric constant d31 of 32pm∕V.

Plasma bolometry using a multislit shutter with piezoelectric actuator

We offer to apply a shutter with a piezoelectric bimorph actuator as a modulator of radiation and particle fluxes. Such shutters may be useful to provide measurements in steady state regimes of tokamaks and stellarators because they allow one to avoid amplifier drifts and to simplify diagnostics calibration. Signal modulation makes it possible to apply the lock-in amplification technique, increasing the sensitivity and reducing the neutron doze collected by sensors. Experiments with pyroelectric sensors (LiTaO3) at 350 Hz modulation frequency have demonstrated the detection limit at 30 Hz equal to 15 μW/cm2, which is comparable to metallic bolometers.