Showing papers on "Bimorph published in 2000"

Piezoelectric ceramic bimorph coupled to thin metal plate as cooling fan for electronic devices

Abstract: Several types of piezoelectric fans for cooling electronic devices were constructed and tested at 60 Hz, 110 V and 220 V, respectively. The aim of the work is to investigate the possibility of replacing the rotary type of fan in some noise-sensitive electronic devices. Different vibrating metal plates were tested and analyzed theoretically. It is found that the resonant frequency of the vibrating plate decreases with the increase of its length ( l ) if the length of the piezoelectric ceramic bimorph ( L ) is kept constant. The series-type fan with l =31.8 mm, made of phosphor bronze vibrating plate (S6), shows the highest value of fan tip displacement of 35.5 mm and produced wind velocity of 3.1 m/s driven by a 220 V, 60 Hz power source.

Optimization of a circular piezoelectric bimorph for a micropump driver

Abstract: Piezoelectric bimorph actuation has been successfully used in numerous types of microdevices, most notably micropumps. However, even for the simple case of circular geometry, analytical treatments are severely limited. This study utilized the finite-element method to optimize the deflection of a circular bimorph consisting of a single piezoelectric actuator, bonding material and elastic plate of finite dimensions. Optimum actuator dimensions were determined for given plate dimensions, actuator-to-plate stiffness ratio and bonding layer thickness. Dimensional analysis was used to present the results for fixed- and pinned-edge conditions in a generalized form for use as a design tool. For an optimally-thick actuator, the optimum actuator-to-plate radius ratio ranged from 0.81 to 1.0, and was independent of the Young's modulus ratio. For thin plates, a bonding layer minimally affected the optimum dimensions. The optimized actuator dimensions based on a model of an actual device were within 13% of the fixed-edge condition.

Mems variable optical attenuator

Abstract: A MEMS (Micro Electro Mechanical System) variable optical attenuator is provided that is capable of optical attenuation over a full range of optical power. The MEMS variable optical attenuator comprises a microelectronic substrate, a MEMS actuator and an optical shutter. The MEMS variable optical attenuator may also comprise a clamping element capable of locking the optical shutter at a desired attenuation position. The variable light attenuator is capable of attenuating optical beams that have their optical axis running parallel and perpendicular to the substrate. Additionally, the MEMS actuator of the present invention may comprise an array of MEMS actuators capable of supplying the optical shutter with greater displacement distances and, thus a fuller range of optical attenuation. In one embodiment of the invention, the MEMS actuator comprises a thermal arched beam actuator. Additionally, the variable optical attenuator of the present invention may be embodied in a thermal bimorph cantilever structure. This alternate embodiment includes a microelectronic substrate and a thermal bimorph cantilever structure having at least two materials of different thermal coefficient of expansion. The thermal bimorph is responsive to thermal activation and moves in the direction of the material having the lower thermal coefficient expansion. Upon activation, the thermal bimorph intercepts the path of the optical beam and provides for the desired level of optical attenuation. The invention also provides for a method of optical attenuation and a method for fabricating an optical attenuator in accordance with the described structures.

Variable capacitor and associated fabrication method

Abstract: A variable capacitor having low loss and a correspondingly high Q is provided. In addition to a substrate, the variable capacitor includes at least one substrate electrode and a substrate capacitor plate that are disposed upon the substrate and formed of a low electrical resistance material, such as HTS material or a thick metal layer. The variable capacitor also includes a bimorph member extending outwardly from the substrate and over the at least one substrate electrode. The bimorph member includes first and second layers formed of materials having different coefficients of thermal expansion. The first and second layers of the bimorph member define at least one bimorph electrode and a bimorph capacitor plate such that the establishment of a voltage differential between the substrate electrode and the bimorph electrode moves the bimorph member relative to the substrate electrode, thereby altering the interelectrode spacing as well as the distance between the capacitor plates. As such, the capacitance of the variable capacitor can be controlled based upon the relative spacing between the bimorph member and the underlying substrate. A method is also provided for micromachining or otherwise fabricating a variable capacitor having an electrode and a capacitor plate formed of a low electrical resistance material such that the resulting variable capacitor has low loss and a correspondingly high Q. The variable capacitor can therefore be employed in high frequency applications, such as required by some tunable filters.

Method of producing micro contact structure and contact probe using same

Abstract: A method of producing a contact structure and a probe card makes it possible to test a semiconductor integrated circuit device formed on a semiconductor wafer having a pin pitch of 0.5 mm or smaller. The contact structure includes a micro contact pin having electric conductivity formed on one end of a beam which is movable in a vertical direction, and a piezoelectric element formed on the beam to drive the beam in the vertical direction. The beam is made of silicon on the surface of which is formed of a conductive thin film, and the micro contact pin has a pyramid shape. The piezoelectric element is a bimorph plate mounted on an upper surface of the beam or both upper and lower surfaces of the beam.

Hybrid microelectromechanical system tunable capacitor and associated fabrication methods

Abstract: A microelectromechanical system (MEMS) tunable capacitor having low loss and a corresponding high Q is provided. The tunable capacitor includes a first substrate having a first capacitor plate disposed thereon. A fixed pivot structure is disposed on the first surface of the first substrate, proximate the first capacitor plate. The fixed pivot structure as a point of attachment for a flexible membrane that extends outward from the fixed pivot and generally overlies the first capacitor plate. A second substrate is attached to the underside of the flexible membrane and a second capacitor plate is disposed thereon such that the first and second capacitor plates face one another in a spaced apart relationship. A MEMS actuator is operably in contact with the flexible membrane for the purpose of providing an actuation force to the flexible membrane, thereby varying the capacitance between the first and second capacitor plates. In one advantageous embodiment of the invention the first and second capacitor plates are formed of an HTS material and the first and second substrates may be formed of a low signal loss material that is compatible with the HTS materials. The MEMS actuator device used to provide actuation to the flexible membrane of the tunable capacitor may include a MEMS electrostatic flexible film actuator, a MEMS thermal arched beam actuator, a MEMS thermal bimorph actuator, a MEMS piezoelectric actuator or any other MEMS actuation device. Additionally, a method for making a tunable capacitor is provided.

Five-port equivalent electric circuit of piezoelectric bimorph beam

Abstract: Electromechanical behavior of a three-layered piezoelectric bimorph beam is represented by an electrically equivalent circuit with impedance elements. Each impedance is determined from the components of the electrically equivalent 5×5 impedance matrix. The derivation of the impedance matrix is based on a bimorph beam theory where vertical and angular displacements at each end of the beam are considered. The impedance matrix thus consist of one electrical, four mechanical and one electromechanical coupling loops. Entire electromechanical flows and efforts accordingly have one electrical and four mechanical ports. For an electromechanical system where other mechanical or electrical components are attached to the bimorph, an equivalent electric circuit of the system can be thus generated by connecting the electrically equivalent impedances to the circuit according to the mechanical boundary conditions or external mechanical components. The characteristics of the electromechanical system, e.g., an electrical admittance, can be obtained from the equivalent circuit. As examples, three different types of mechanical boundary conditions — free, simply supported and cantilevered — are considered, and the equivalent circuits are drawn with each port opened or closed according to the boundary conditions. Two examples of external mechanical systems attached to the bimorph are also shown, i.e., a cantilevered bimorph beam with a mass–spring–damper system attached to its free end, and a segmented piezoelectric bimorph beam with an extended substrate arm. In each case, an equivalent circuit is also drawn and the electrical admittance is directly derived from the circuit. The resonance and antiresonance frequencies are accordingly calculated, and it is found that the five-port equivalent electric circuit of the piezoelectric bimorph beam presented in this paper yields an exact expression for the vibration of the piezoelectric bimorph.

Integrated atomic force microscopy array probe with metal-oxide-semiconductor field effect transistor stress sensor, thermal bimorph actuator, and on-chip complementary metal-oxide-semiconductor electronics

Abstract: A microfabricated 2×1 array of active and self-detecting cantilevers is presented for applications in atomic force microscopy (AFM). The integrated deflection sensor is based on a stress sensing metal–oxide–semiconductor transistor. Full custom complementary metal–oxide–semiconductor amplifiers for signal readout are combined on the same chip. A sensor sensitivity of 2.25 mV/nm, or a change in current ΔId/Id=2.8×10−6/nm, was obtained at the final output stage. Three Al–Si thermal bimorph actuators are integrated on each cantilever for self-excitation and feedback actuation. The efficiencies of the heaters are 2.4–4.7 K/mW. In the experimental setup, a maximum displacement of 8 μm was achieved at 45 mW input. A pair of parallel AFM images in the constant height mode, a typical tapping mode image, and a constant force image with 1.3 μm high features have been successfully taken with the array probe.

Two-dimensional thermally actuated optical microprojector

Abstract: A dual-axis, raster-scanning laser display based on a monolithic micromachined scanner is presented. The scanner consists of a mirror located at the end of a thermally actuated bimorph beam. The novelty of the device is that the two orthogonal angular motions are given by the same "L"-shaped cantilever, which is simultaneously excited at non-resonance (frame scanning) and at resonance (raster scanning). The demonstration microdevice has a raster-scanning frequency at 1345 Hz that allows, if combined with 10 Hz sawtooth Game signal, the definition of more than 100 lines. Mechanical scan amplitudes over 15 degrees in two orthogonal directions were achieved. The typical power consumption is 5 mW. (C) 2000 Elsevier Science S.A. All rights reserved.

Novel multibridge-structured piezoelectric microdevice for scanning force microscopy

Abstract: In this article we report the structure and the microfabrication method of a novel micro-scanning force microscopy (SFM) device. It is a lead zirconate titanite (PZT) bimorph structure in the shape of a cantilever supported by bridges. Electric fields applied to the separated sections of the electrodes on the levers can induce lever deflection and actuate the tip in x, y, and z directions. The cantilever can vibrate and sense its own vibration amplitude to detect the surface topography in the cyclic contact SFM mode. In the fabrication process, the sol–gel method is modified for constructing high quality PZT films 3 μm thick. The single bridge device has shown microscopy sensitivity of 0.32 nA/nm in a vertical direction, with actuation sensitivities of 70–80 nm/V in a lateral direction. The multibridged structure has been proven to be effective in elevating the eigenfrequency, which is very important for improving the SPM data rate.

Design and fabrication of a novel piezoelectric multilayer actuator by thick-film screen printing technology

Abstract: A novel structured multilayer piezoelectric lead zirconate titanate (PZT) actuator that combined the merits of high displacement/voltage sensitivity, high resonance frequency and low costs has been designed and successfully fabricated using the thick-film screen printing technology. Its structural, dielectric, and piezoelectric properties were also characterized. Experimental results show that the average grain size, dielectric, and piezoelectric properties of the PZT thick-film multilayer actuators are strongly dependent on processing conditions. Under the driving voltage of 10 V, a displacement value of 1.57 μm is obtained, and the corresponding resonance frequency is 56.9 kHz. Only a few layers are required to construct this multimorph actuator, instead of tens or even hundreds of layers that a conventional stacked multilayer actuator requires in order to realize a large displacement, thus greatly reducing manufacturing costs. The multimorph actuator presented in this paper provides a valuable alternative for actuator applications beyond those available with the popular bimorph and longitudinal multilayer actuators, such as for the second-stage track following control in computer hard disk drives.

Dual-cantilever AFM probe for combining fast and coarse imaging with high-resolution imaging

Abstract: This paper presents a new scanning probe concept based on an integrated dual-cantilever device, which has been designed to reduce the tip-wear problem. It consists of two cantilevers, one having a robust blunt tip, the other having a sharp tip. By means of integrated bimorph actuators, such a cantilever can be used to switch between coarse and fast imaging with the blunt tip, and high-resolution imaging with the sharp tip. Hence the delicate sharp tip is used only when high resolution is required, which greatly increases the probe's lifetime. A high-sensitivity, constricted piezoresistive strain sensor is used for high-resolution imaging. Imaging with the dual-cantilever probe has been demonstrated successfully.

Fully programmable MEMS ciliary actuator arrays for micromanipulation tasks

Abstract: The first micromachined bimorph organic ciliary array with on-chip CMOS circuitry is presented. This device is composed of an 8/spl times/8 array of cells each having four orthogonally oriented actuators in on overall die-size of 9.4 mm/spl times/9.4 mm. The polyimide based actuators were fabricated directly above the selection and drive circuitry. Selection and activation of actuators in this array shows that integration was successful. The integration of CMOS electronics and MEMS micromechanisms allows the implementation of new task-level micromanipulation strategies. New low-level control algorithms (actuator gaits) were also demonstrated. The array was programmed to perform several kinds of manipulation tasks, including linear translation, diagonal motion, as well as vector field operations such as squeeze field and radial field orienting and centering. Preliminary experiments were also performed using thin silicon dice of about 3 mm/spl times/3 mm/spl times/0.5 mm size as the object being moved.

Cymbal transducers: a review

Abstract: The cymbal transducers consist of a piezoelectric disk (poled in the thickness direction) sandwiched between two cymbal-shaped metal end caps. The metal caps serve as a mechanical transformer which transforms the high impedance, small extensional motion of the ceramic into low impedance, large flexural motion of the shell. The cymbal was originally designed as an actuator, which provides a sizable displacement as well as a large generative force, bridging the gap between the two most common actuators, the bimorph and the multilayer. It was later proposed as a shallow water sound projector and receiver. Single elements are characterized by high Q, low efficiency and medium power output capability. Their low cost and thin profile allow the transducer to be assembled into large flexible arrays. A 5/spl times/20 prototype array was built and tested. It has a broadband response in the frequency range between 17 kHz and 100 kHz. The array is flexible and easily conforms to a curved surface. Finite element code ATILA was used successfully in modeling and optimizing the single element transducer. Several modifications were investigated for various applications with the aid of computer modeling. Among them are the double-dipper (deep submergence), the double-driver (unidirective beam pattern) and the smart caps (adjustable resonance frequency).

Elastic properties of magnetostrictive thin films using bending and torsion resonances of a bimorph

Abstract: The modification of the elastic properties of giant magnetostriction alloy films due to an applied magnetic field (the ΔE effect), has been studied. Two different types of films were deposited on Si substrates: (i) single layers of TbDyFeCo alloys typically 1000 nm thick and (ii) nanocomposite multilayer films of FeCo/TbFeCo each having a typical thickness of 6 nm. Both types of films were rendered magnetically anisotropic with a well defined in-plane easy axis. Rectangular samples were cut out of these bimorphs and firmly glued at one end to a heavy base to form a simple cantilever structure. The variations of film elastic moduli were deduced from the shifts of the cantilever resonance frequencies as a function of bias field for two basic configurations: (i) field applied along the easy axis and (ii) field applied along the hard axis. In contrast with previous work, both flexural and torsion resonance modes were excited and studied. As a result the field induced variations of both planar traction modulus...

Vibrations and static responses of asymmetric bimorph disks of piezoelectric ceramics

Abstract: In an earlier article, the flexural vibrations in bimorph disks and extensional vibrations in homogeneous disks of piezoelectric ceramics were studied. In the present paper, the coupled flexural and extensional vibrations and static responses in an asymmetric bimorph disk, which is formed by bonding together two piezoelectric ceramic disks of unequal thickness and opposite polarization, are investigated. Governing equations of coupled motions for asymmetric bimorphs are deduced from the recently derived 2-D, first-order equations for piezoelectric crystal plates with thickness-graded material properties. Then, closed form solutions of these equations for circular disks are obtained for free vibrations, piezoelectrically forced vibrations, and responses under static voltage difference. Resonance frequencies, distribution of displacements and surface charges, impedances, and static responses are calculated for asymmetric bimorph disks of various thickness ratios and diameter-to-thickness ratios. Experimental data on resonances and impedances are obtained for asymmetric bimorph disks of PZT-857 for different thickness ratios. Comparisons of predicted and measured results show that the agreements are close.

Three-dimensional analysis of an antiparallel piezoelectric bimorph

Abstract: Three-dimensional electromechanical responses of a piezoelectric bimorph are studied. The bimorph is antiparallel in the sense that it consists of two identical, plate-like piezoelectric elements with opposite poling directions. Both the top and bottom surfaces of the bimorph are fully covered with negligibly thin conductive electrodes. By introducing a small parameter and using the transfer matrix method it is shown that a three-dimensional solution of the problem can be readily constructed, provided the solution to a set of two-dimensional equations very similar to those in the classic plate theory is obtainable. The three-dimensional solution satisfies all the field equations as well as the boundary conditions on the major surfaces and at the interface between the two piezoelectric plates. In many special cases, the electric edge condition can be fulfilled point by point, and thus the solution is exact in Saint-Venant's sense. The formulation and new analytical results for a strip-shaped cantilever bimorph under the action of applied voltage and end moment are presented.

A two-way membrane-type micro-actuator with continuous deflections

Abstract: This paper presents design, simulation, fabrication, and testing of a novel two-way micro-membrane actuator able to deflect in both upward and downward directions with continuous deflections. The design concept, to realize two-way continuous movement, is achieved by arranging different bimorph structures at different regions of the actuator with two kinds of boundary conditions. The actuator comprises of a square membrane with four bimorph beams and one central bimorph plate on it. The material (e.g. aluminum) on the top layer of the bimorph beams and plate has a larger thermal expansion coefficient than the material (e.g. silicon dioxide) of the membrane. The driving voltages in the two operating modes are both less than 3.5 V at about 350 mW maximum power consumption for an 1 mm2 membrane actuator. The upward and downward deflections achieved up to 50 and 15 µm with maximum simulated temperatures less than 420 and 150 °C, respectively. A finite-element model is built to simulate the thermal mechanical behaviors that are compared with the experimental results. The design parameters influencing the deflections of the actuator are also discussed.

A new intelligent thin-shell element

Abstract: In this paper, a new three-dimensional thin-shell structure containing an integrated distributed piezoelectric sensor and actuator is proposed. The distributed piezoelectric sensor layer monitors the structural shape deformation due to the direct effect and the distributed actuator layer suppresses the deflection via the converse piezoelectric effect. A finite-element formulation is presented for modelling the dynamic as well as static response of the laminated shell with piezoelectric sensors/actuators. An eight-node and 40 degrees of freedom shell element is built. The performance of the shell elements is improved by a reduced integration technique. The shell element is verified by calculating a piezoelectric polymeric PVDF bimorph beam. The results agreed fairly well with those obtained through theoretical analysis by Tzou and Tseng and Hwang and Park.

CMOS Integrated Organic Ciliary Actuator Arrays For General-Purpose Micromanipulation Tasks

Abstract: The first micromachined bimorph organic ciliary array with on-chip CMOS circuitry is presented. This device is composed of an 8 × 8 array of cells each having four orthogonally oriented actuators in an overall die size of 9.4mm × 9.4mm. The polyimide based actuators were fabricated directly above the selection and drive circuitry. Selection and activation of actuators in this array shows that integration was successful.

Functionally gradient piezoelectric bimorph-type actuator

Abstract: A new type of piezoelectric actuator has been developed by combining two piezoelectric Functionally Gradient Material (FGM) composite laminates into a bimorph to produce an actuator with large out of plane displacements while having reduced mid-plane stresses. This combination of high displacement with reduced stress keeps the benefit of the bimorph while reducing one of its drawbacks. These properties are varied symmetrically about the mid-plane of the actuator with the entire actuator being poled in one direction through the thickness of the device. These deices are produced by stacking individual layers of piezoelectric fibers in a modified epoxy matrix with varying fiber volume fraction form layer to layer thereby leading to varying material properties through the thickness of the composite. The focus of this work has been to use the finite element method to first predict the material properties for individual piezoelectric fiber based layers using a symmetrical unit cell model, which allowed the inter-layer and intra-layer volume fractions to be varied independently reflecting the rectangular packing of fibers present in the actual devices. And, then to predict the behavior of the actual composite devices using these predicted properties.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Impedance and admittance matrices of symmetric piezoelectric annular bimorphs and their applications

Abstract: The 5×5 impedance and admittance matrices of a symmetric triple-layer piezoelectric annular bimorph (PAB) are presented and the PAB with the piezoelectric layers partially covering the shim layer in harmonic motion is analyzed using the matrices. The electromechanical flow vectors are defined as the mechanical displacements and rotations at the inner and outer boundaries and the electric current of the piezoelectric layer; the conjugate parameters, i.e., the electromechanical effort vectors, are accordingly defined. The impedance matrix which relates the flow vector with the effort vector is divided into three matrices, the mechanical, electrical, and electromechanical coupling impedance matrices; each matrix is represented by a block network with five ports. The resonance and the antiresonance frequencies and the effective electromechanical coupling factors of the PAB excited by the partially covering piezoelectric layers are then calculated for various boundary conditions imposed at the inner and outer surfaces. The numerical results by the impedance matrix are compared with those by the finite element methods; they are in excellent agreement with each other. It is also shown that the matrix representations can be easily applied to the piezoelectric circular bimorph (PCB) with the extended shim layer.

Optical switching system

Abstract: An optical switching device switches optical signals completely within optical media, from an arbitrary number of N input optical fibers to a set of M output optical fibers. The invention uses a thermally-activated bimorph optical switch to redirect optical radiation emitted by a laser light source, or from the end of an optical fiber, to an input end of another optical fiber. The modulated optical radiation from the input fiber optic bundle is collimated into parallel beams and projected in free space across the tops of an array of microcantilever bimorph optical switches. When selected, a particular switch is activated, thereby causing a first bimorph switch element to pop up, and intercept and reflect the optical radiation at an angle approximately 90° to the original optical path direction. This reflected radiation is intercepted by another essentially identical bimorph switch element, located above or below the first switch element, that directs the radiation in a plane essentially parallel to that of the original beam plane, but above or below the original plane, and at approximately right angles to the original beam direction. The optical radiation is directed by the second switch element to output optical fiber collimating optics. This radiation is then coupled into the selected output optical fiber.

Giant magnetostriction thin films for multi-cantilever micro-structures driving

Abstract: First results on the realisation of a micrometer GaInAs multi-cantilever structure (50×30×1 μm 3 each) driven by amorphous TbFe magnetostrictive thin films are presented. Magneto-elastic properties of the cantilevers were studied by dynamic excitation methods. A resonance of the bimorph cantilevers was observed at an excitation frequency of 0.8 MHz with a Q -factor of about 10 3 . The coercive force of the magnetic films sputtered on micro-cantilevers was found to be H c =8 Oe.

Optimal design of a PZT bimorph actuator for minimally invasive surgery

Abstract: A metamodel-based presented is developed to optimize the force and displacement performance of a piezoceramic bimorph actuator. A segmented design with a variable piezoceramic layer thickness is proposed, where the thicknesses of discrete piezoceramic segments are used as the design variables. Design of experiments and metamodeling techniques are employed to construct computationally inexpensive approximations of finite element simulations of the PZT bimorph actuator. The metamodels are then used in lieu of the actual FEM for optimization. Design objectives include maximum tip deflection, maximum grasping force, and maximum work available at the tip. The metamodels are also used to rapidly generate the design space and identify the Pareto frontier for the competing design objectives of maximum deflection and maximum force. The accuracy and efficacy of two types of metamodels -- response surfaces and kriging models -- are compared in this study. By optimizing the thickness of the piezoceramic layers, and by allowing the voltage applied to each segment to vary, dramatic improvements in deflection and force are obtained when compared to a standard straight bimorph actuator. The motivation for this design is the need in the field of minimally invasive surgery for improved grasping tools, where a pair of optimized bimorph actuators can be used as a simple grasping device.

Dynamic analysis of an optical beam deflector

Abstract: This paper studies the dynamic behavior of an optical beam deflector that is composed of piezoelectric bimorphs with both ends clamped The bimorph bends so that a mirror affixed onto its central position titles by the applied voltage in the electrodes of the deflector The equations of motion describing the vibration behavior of the completely distributed parameter model are derived by Hamilton's principle The analytic model is used to predict the effect of the applied voltage and split electrodes, and to obtain an equivalent configuration of the beam deflector with external moments The finite element method and a convergent numerical integration scheme are used to simulate the dynamic responses and to validate the theoretical analysis

Mechanical nonlinearities in a magnetically actuated resonator

Abstract: This paper presents mechanical characteristics of a silicon-based magnetic micro-actuator - a test device, which was developed for optical-scanner applications. A magneto-elastic bimorph is used for the actuation. Deflections over 20 µm have been measured in a torsion mode, for an excitation field of 3 mT. The effect of large deflections generated anharmonic behavior of the mechanical structure working near resonance. Experimental results are analyzed with reference to a theoretical model and by a comparison with FEM simulations.