Showing papers on "Bimorph published in 2001"

Disk drive actuator arm with microactuated read/write head positioning

Abstract: The present invention is embodied in an actuator arm which is mounted to a primary actuator. The primary actuator positions the actuator arm, with a read/write head mounted to the actuator arm, across a data storage disk. The actuator arm comprises an inboard portion, an outboard portion and a pair of bimorph actuators. The inboard portion has a longitudinal axis and is attached to the primary actuator. The outboard portion has the read/write head mounted onto it. The pair of bimorph actuators are deflectable together in a common direction and are connected between the inboard and the outboard portions. Upon deflection of the bimorph actuators in the same direction, the outboard portion is translated along an at least nearly straight line transverse to the longitudinal axis of the inboard portion. This transverse motion allows the read/write head to be kept substantially within a plane parallel to the surface of the data storage disk, preventing damage caused by possible contact between slider and the disk surface from rolling the slider due to out-of-plane motions. Further, the use of bimorph actuators provide increased displacements of the read/write head. Also, since the head displacement is not a function of microactuator's position along the actuator arm, the actuator arm can be shorter, allowing for use in compact disk drives.

Modeling piezoelectric and piezomagnetic devices and structures via equivalent networks

Abstract: A history of equivalent circuit modeling of acoustic structures is presented. This is followed by a tutorial development of their use to represent piezoelectric (PE) and piezomagnetic (PM) plate transducers and bimorph cantilever beams for the purpose of facilitating transition of modern micro/nanotechnology creations to practical sensor, actuator, and transducer applications. Circuit approximations of various types are derived from the more general networks.

Surface micromachined piezoelectric accelerometers (PiXLs)

Abstract: The design, fabrication, and characterization of surface micromachined piezoelectric accelerometers are presented in this paper. The thin-film accelerometers employ zinc oxide (ZnO) as the active piezoelectric material, with different designs using either polysilicon or ZnO bimorph substrates. Sensitivity analyses are presented for two specific sensor designs. Guidelines for design optimization are derived by combining expressions for device sensitivity and resonant frequency. Two microfabrication techniques based on SiO/sub 2/ and Si sacrificial etching are outlined. Techniques for residual stress compensation in both fabrication processes are discussed. Accelerometers based on both processes have been fabricated and characterized. A sensitivity of 0.95 fC/g and resonant frequency of 3.3 kHz has been realized for a simple cantilever accelerometer fabricated using the sacrificial SiO/sub 2/ process. Sensors fabricated in the sacrificial Si process with discrete proof masses have exhibited sensitivities of 13.3 fC/g and 44.7 fC/g at resonant frequencies of 2.23 kHz and 1.02 kHz, respectively.

Synthetic jet actuators

Abstract: A first embodiment of the present invention provides a vortex generator in the form of a flexible piezoelectric actuator blade disposed in a wall of a flowpath, such as an airfoil. Another embodiment provides a synthetic jet actuator in which a pair of bimorph piezoelectric plates are connected by a flexible hinge.

Meshless analysis of piezoelectric devices

Abstract: The sensor and actuator properties of piezoelectric materials make them well suited for applications in a variety of microelectromechanical systems (MEMS). Simulating the response of piezoelectric devices requires solving coupled electrical and mechanical partial differential equations. In this paper, we have implemented a meshless point collocation method (PCM) to solve the governing equations. Interpolation functions are constructed from a reproducing kernel approximation, and the governing equations are discretized using a collocation approach. PCM is implemented using either a relaxation algorithm or a fully-coupled algorithm. Comparisons between the two algorithms are given. To demonstrate the performance of PCM, the behavior of two static single-layer problems and a piezoelectric bimorph have been modeled. The bimorph analysis is extended to model a prototype MEMS device.

Fabrication and test of thermal vertical bimorph actuators for movement in the wafer plane

Abstract: We have fabricated thermal actuators based on vertical bimorphs, which consist of silicon beams side-coated with aluminium. When they are heated by an electrical current they bend like a bimetal and produce movement in the wafer plane. The fabrication process is based on silicon-on-insulator substrates and uses standard silicon micromachining techniques combined with a special aluminium sidewall deposition process. The displacement has been measured as a function of the input power and the results have been compared with an FEA-simulation.

Micromirrors for Adaptive-Optics Arrays

Abstract: We present a micromachined mirror array for use in adaptive optics. Piston motions of more than 6 µm as well as tip/tilt motions of 11 mrad (0.65°) are demonstrated. Single-crystal-silicon mirrors are assembled onto electrostatic parallel-plate actuators. The actuators lift off the substrate after microstructure release as a consequence of residual stresses in nickel-polysilicon bimorph flexures. The assembled mirrors provide fill factors of 95%. Peak-to-valley surface variations are smaller than 30 nm over a 464 µm-diameter (vertex-to-vertex) mirror segment.

Omnidirectional walking microrobot realized by thermal microactuator arrays

Abstract: An omnidirectional mobile microrobot realized by microelectromechanical system (MEMS) actuator arrays is presented. The microrobot consists of two rigidly connected microcilia array chips, each having an 8 8 array of “motion pixels,” which are composed of four orthogonally oriented thermal bimorph actuators. This allows for reliable, accurate motion in three degrees of freedom x y θ in the plane, a first for a microrobot of this kind. The microrobot is approximately 3cm in length, 1cm in width, 1mm in height, and has a mass of less than half a gram. By varying the input power, actuation frequency and motion gait strategy the velocity of the chip can be precisely controlled. Motion in three degrees of freedom has been demonstrated and a maximum velocity of 635 µm/s and carrying capacity greater than 1.448 g (two 8-pin ICs) has been observed. The microrobot has been characterized extensively and a model for its performance is described.

Analysis of the asymmetric triple-layered piezoelectric bimorph using equivalent circuit models

Abstract: An eight-port impedance matrix and an equivalent circuit are presented for the analysis of an asymmetric triple-layered piezoelectric bimorph with separate electrical ports. The separate electric ports for the top and bottom piezoelectric layers operate independently of each other: they generate and/or sense the coupled extensional and flexural motions. Taking into account shear and rotatory inertia, the eight-port impedance model is first obtained for the bimorph. The electromechanical behavior of the piezoelectric layers, and the mechanical motions of the bimorph, are separately represented by equivalent circuits with common ports. Connecting the circuits through the common ports then leads to the overall equivalent circuit. It is demonstrated that the resonance/antiresonance frequencies and the sensor-to-actuator signal of the cantilevered bimorph for various length-to-thickness ratios can be effectively calculated by the application of the electrical network theory to the equivalent circuit. It is als...

2D-Elasticity Analysis of FGM Piezo-Laminates Under Cylindrical Bending

Abstract: Elastic behavior of piezo-laminates under cylindrical bending is studied using 2D-elasticity model and classical lamination theory (CLT). The stresses and out-of-plane displacements are obtained for standard piezoelectric bimorph and newly proposed piezoelectric laminate with functionally graded microstructure (FGM) plates under cylindrical bending generated by electric field throughout the thickness of the laminate. The FGM piezoelectric laminates are composite materials whose electroelastic properties are varied through their thickness. The properties can vary in a continuous or a stepwise manner. The FGM laminate investigated in this paper is of a stepwise FGM where different piezoelectric composite layers are stacked to form FGM laminate. The feasibility of FGM laminate is studied. The limitations of CLT are investigated against the 2D-elasticity model. CLT solutions are found to coincide well with the elasticity solutions for high aspect ratios while the CLT solutions gave poor results compared to the 2D-elasticity solutions for low aspect ratios. The analytical models, CLT and 2D-elasticity, are investigated against the Finite Element Methods (FEM). Standard bimorph of piezoelectric actuator was fabricated and the displacement measurements resulted in a good agreement to the analytical and FEM results.

Micromachined, flip–chip assembled, actuatable contacts for use in high density interconnection in electronics packaging

Abstract: Using flip–chip assembly, micromachined contacts can be used to create a high density, actuatable electronics packaging technology. Internal residual stress is used to press bimorph beam connectors upwards against a device chip. The connectors’ actuation behavior is described, including appropriate mathematical models. The electrostatically actuated beams will disconnect when driven by a 53 V signal and will reconnect when voltage falls below 43 V. Analytic models, which account for the non-linearity present in a curved cantilever beam, are presented. When switching signals, reconnection occurs in as little as 5.8 μs, disconnection occurs in as little as 4.0 μs. A microconnector’s current carrying capability can be as high as 285.3 mA and its maximum power dissipation as high as 1.47 W.

Adaptive optical elements for laser beam control

Abstract: Bimorph mirrors for laser beam correction and formation were developed and investigated. Different types of substrates and active piezoceramics materials were considered to fabricate temperature independent shape of the mirror surface and to maximize the sensitivity of the mirror. High reflectivity coatings for different wavelengths were studied.

Photostrictive actuators - New perspective

Abstract: Photostrictive materials, exhibiting light-induced strains, are of interest for future generation wireless remote control photo-actuators, micro-actuators, and micro-sensors applications. (Pb, La)(Zr, Ti) O3 (PLZT) ceramics doped with WO3 exhibit large photostriction under uniform illumination of near-ultraviolet light. Using a bimorph configuration, a photo-driven relay and a micro walking device have been demonstrated. However, for the fabrication of these devices, higher response speed must be achieved. The present paper reviews a new theoretical model for photovoltaic effect first, then enhanced performance through sample thickness and surface characteristics, finally its potential future applications.

Microactuator for dynamic controlling head-media interaction and fly-height

Abstract: A microactuating suspension assembly used for a disc drive is disclosed. The microactuating suspension assembly has a suspension load beam and a microactuator placed on the suspension load beam for bending the suspension load beam at the front end thereof during a sustained period of data read/write time and thus achieving a desired average fly-height which is different from an unaltered average fly-height which would have been achieved without the microactuator. In particular, the microactuating suspension assembly can be used to achieve a very low fly-height. Additionally, very large bandwidth and very short seeking time is made possible when a bimorph piezoelectric microactuator is used.

Analysis of an asymmetrical piezoelectric annular bimorph using impedance and admittance matrices

Abstract: A theoretical model is presented for the analysis of an asymmetrical piezoelectric annular bimorph (APAB) in dynamic harmonic motion. The APAB is assumed to be so thin that the thickness dependent stresses vanish throughout. The conjugate parameters of the admittance and impedance matrices are derived using the variational principle. Both the extensional and flexural motions are considered in deriving the motional equations and the boundary conditions. By using the symmetry characteristic of the admittance matrix, the derivation procedure for the impedance and admittance matrices is thus greatly simplified. The resonance and antiresonance frequencies and the effective electromechanical coupling factors are calculated using the matrices. These present methods are applied to three special cases: a single piezoelectric ring in extensional motion, a triple-layer APAB in series or parallel connection, and a triple-layer APAB with sensor and actuator. The results are compared with previous publication and finite element methods, and it is found that the present methods are very effective in analyzing the piezoelectric multilayer annular transducers.

Multi-degree-of-freedom displacement measurement system for milli-structures

Abstract: A new multi-degree-of-freedom measurement system for milli-structures is presented. This methodology is based on optical beam deflection method and triangulation. It employs a diffraction grating as a reflective object, which reflects an incident laser beam into several directions. To obtain the pose information of a measured object, the detecting positions of zeroth- and first-order diffracted rays are measured using three two-dimensional detectors. From these values, we can calculate six-degree-of-freedom displacement through a kinematic analysis. The performance was evaluated with resolution, measurement errors and crosstalk. The results show that measurement errors and maximum crosstalk are within ±0.5 µm in translation and ±2'' in rotation. As an application, we measured the multi-DOF motion of a bimorph type PZT actuator and obtained its frequency response function.

Optical shutter for spectroscopy instrument

Abstract: Spectroscopy apparatus for spectrochemical analysis of a sample having an excitation source (60) for providing spectral light (62) of the sample for analysis. The spectral light (62) is analysed via an optical system (64-66-68) that includes a polychromator (70, 74-80) and solid state multielement array detector (82). The elements (i.e. pixels) of the detector (82) are serially read by means (84) to provide light intensity measurements as a function of wavelength. A problem is that the elements (pixels) of the detector (82) continue to accumulate charge during the serial read-out. This is avoided by providing an optical shutter (72) for blocking the spectral light (62) whilst elements (pixels) of the detector (82) are being serially read. Shutter (72) has a piezoelectric actuator which is preferably a bimorph mounted as a cantilever. It is preferably located adjacent to the entrance aperture (70) of the polychromator. Bimorph structures for the actuator and drive and protective circuit arrangements are also disclosed.

Thermal microactuators for optical purpose

Abstract: The core of the project was to design a moveable micromirror array with the most optimal dependence of the optically active area, the deflection angles and the micromirror power consumption. The matrix of 10/spl times/20 micromirrors uses a thermal actuated principle. The micromirror was designed using an industrial 0.8 /spl mu/m double metal CMOS process followed by one single postprocessing step and anisotropic silicon etch. The device consists of one cantilever beam supporting the mirror plate. The beam is a bimorph sandwich of aluminium and silicon dioxide enclosing polysilicon heating resistor. The control electronics contains 20-bit edge-triggered shift register with serial data entry and an output from each of the twenty stages (flip-flop). The output buffer is a driver for the CMOS switch (transfergate) which connects current (Pad Supply for the beam) to the thermal actuator (beam). The ANSYS program was used for the mechanical simulation of thermally actuated micromirror.

Integrated micro-opto-electro-mechanical laser scanner

Abstract: A micro-optical-electrical-mechanical laser scanner is configured from a silicon-on-insulator substrate having a silicon substrate layer, a buried oxide layer, and a single crystal silicon device layer. A first device layer portion having a micro-mirror fabricated therefrom. A laser is connected to a second device layer portion, and a hinge connects the first device layer portion and the second device layer portion. The hinge is formed with a bimorph material, wherein the bimorph material creates built-in stresses in the hinge. The bimorph hinge moves the released micro-mirror out of the horizontal plane to a position for either directly or indirectly reflecting laser light emitted from the laser.

Domain configuration and switching contributions to the enhanced performance of rainbow actuators

Abstract: Stress-biased actuators, such as Rainbow and ThunderTM devices, offer enhanced displacement performance compared to unimorph and bimorph actuators. Quantifying the relative contributions of mechanics (layer thickness ratio) versus stress effects on actuator performance has proven difficult. In this paper, the importance of domain switching and altered domain configuration on actuator performance is considered. X-ray diffraction has been used to characterize the initial domain configuration in the surface region of the actuators, as well as the domain switching characteristics of the devices under moderate electric fields. Samples with different reduced layer thicknesses were fabricated to alter device stress state, and consequently, domain configuration and switching characteristics. Compared to poled polycrystalline ceramics of the same composition, Rainbow actuators display a slightly higher a-domain population in the surface region of the devices. Interestingly, despite the presence of comparatively large lateral tensile stresses in this region of the device, x-ray diffraction indicates these devices also display greater 90 degree(s) (a- to c-domain) switching, which contributes to the large displacement responses that are observed. The contribution of stress to the enhanced performance of Rainbow and ThunderTM devices is, thus, more accurately described as arising from a change in the initial domain configuration together with minimal suppression in the switching response under high lateral tensile stresses, rather than simply a stress-enhancement of domain switching. The effects of stress on the initial domain configuration and switching response were quantified to define the specific role of stress on the electromechanical response of the devices.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Study on robots with PZT actuator for small pipe

Abstract: This paper presents two kinds of experimental microrobot with PZT actuator for small pipe. The first one is with stacked PZT actuator for climbing /spl phi/ 10 mm pipe; this robot can carry a microgripper. The other one is with bimorph PZT actuator for climbing /spl phi/ 20 mm pipe; it can carry a CCD camera for detecting cracks or fine holes on inner wall of pipe. These two kinds of robots can move in vertical pipe up/down at speed of 4-6 mm, 17-22 mm/s, respectively. Moving principle, structure design and performance characteristics were presented in the paper.

Piezoelectric element, ink-jet recorder head and manufacture thereof

Abstract: PROBLEM TO BE SOLVED: To suppress the variation of the sensitivity or of displacement of a piezoelectric element to a low level and downsize it. SOLUTION: This piezoelectric element comprises a lower electrode 102, a first and second piezoelectric films 104 of 3 μm thickness each, and an upper electrode 105 formed on a (100)MgO single-crystal film-formed substrate 101. The first and second piezoelectric films 103, 104 are formed continuously by sputtering at mutually different substrate temps., such that, e.g. their polarization directions are mutually reverse, as shown by arrow marks A, B on the drawing, thus forming a piezoelectric element having a thin-film bimorph structure.

Two-dimensional modelling of laminated piezoelectric composites: analysis and numerical results

Abstract: We propose a new approach to laminated piezoelectric plates based on a refinement of the electric potential as function of the thickness coordinate of the laminate and accounting for shear effects. Moreover, the variation of the electric potential as function of the thickness coordinate is modelled for each layer of the laminate. The equation for the laminated piezoelectric plate are then obtained by using a variational formulation involving mechanical surface loads or prescribed electric potential on the top and bottom faces of the plate. In addition to the equations for the generalized stress resultants (due to the shear effects), the equation of the electric charge conservation is also deduced for the 2D model. Particular attention is devoted to the single piezoelectric plate and bimorph structure and the through-thickness distribution of the displacements, electric potential as well as stresses are given for different kinds of electromechanical loads. The results thus obtained are compared to those provided by a finite element method performed for the full 3D model. A good agreement is observed for plates made of layers of PZT-4 piezoelectric material. The comparison ascertains the effectiveness of the present 2D approach to piezoelectric laminates.

Piston control with adaptive optics in stellar interferometry - Application to the GI2T interferometer and bimorph mirrors

Abstract: The general purpose of an adaptive optics system is to correct for the wavefront corrugations due to atmospheric turbulence. When applied to a stellar interferometer, care must be taken in the control of the mean optical path length, commonly called differential piston. This paper defines a general formalism for the piston control of a deformable mirror in the linear regime. It is shown that the usual filtering of the piston mode in the command space is not sufficient, mostly in the case of a bimorph mirror. Another algorithm is proposed to cancel in the command space the piston produced in the pupil space. This analysis is confirmed by simulations in the case of the GI2T interferometer located on Plateau de Calern, France. The contrast of the interference fringes is severely reduced in the case of a classical wavefront correction, even in short exposures, but is negligible with our algorithm, assuming a realistic calibration of the mirror. For this purpose, a simple concept for the calibration of the piston induced by a deformable mirror is proposed.

Ring Type Uni/Bimorph Piezoelectric Actuators

Abstract: This paper presents a ring type piezoelectric actuator that combines a ring-shaped piezoelectric component with a thin metal disc. In this actuator, the ring-shaped piezoelectric ceramic produces a radial contraction or expansion, and results in a large flexural displacement of the center of the metal disc. When the PZT ring under the metal disc contracts, the unbounded portion at the center of the disc is permitted to bend with a larger curve in positive (upper) direction. Both experimental results and FEM analysis support the new concept and confirm that the ring type uni/bimorph (ring-morph) configuration has a larger displacement output than that of conventional disc type uni/bimorph actuators with comparable dimensions.

1D and 2D scanning mirrors using thermal buckle-beam actuation

Abstract: Micromirrors with linear deflection behaviors have been found useful for systems requiring 1D and 2D optical scanning patterns and are solutions for low-cost vector or video raster image generators. The advantages of thermal buckle-beam and bimorph actuators are high resulting force, low MEMS area and low voltage requirements. The devices presented in this paper can achieve modest deflection angles at relatively high frequencies. The mirror actuators consists of a doubly clamped array of polysilicon beams that are Joule heated and allowed to buckle out-of-plane. Instead of utilizing the usual linear displacement, a torque is derived from a coupling beam attached across the buckling beams at the point of the maximum derivative of buckle. As the beams buckle, the torque causes the mirror to be rotated away from the substrate. Non-resonant, near-linear mirror deflection response has been achieved with a maximum deflection of six mechanical degrees at a frequency of a few KHz. Employing a high Q resonant structure, a frequency of 16 KHz has been attained with a 1D mirror scanner at a maximum mechanical deflection of around 20 degrees. 1D and 2D scanning mirror devices have been built and will be reviewed in this paper.

Performance of the SPring-8 modular piezoelectric bimorph mirror prototype

Abstract: This paper reports on the performances of a test prototype mirror, based on the Piezoelectroic Bimorph Mirror technology, which has been designed and manufactured (in collaboration with the French optical company SESO) for the national Japanese 8 GeV storage ring Spring-8. The device consists of two 150 mm long modules assembled side-by-side. It exhibits superior surface quality with respect to previously manufactured long piezoelectric bimorph mirrors, as the junctions between modules do not introduce any distortion on the reflecting surface. The mirror can effectively compensate low frequency components of the figure error/waviness left by polishing. Two different simple optimisation methods have been validated: ex-situ in the metrology lab (Adaptive Optics correction and control algorithm) and, for the first time, in-situ at the beamline (Hartmann test). After optimisation with coherent x-rays at the 1 km long SPring-8 beamline, elliptical shaping was achieved with sub (mu) rad level precision for the slope error rms. The associated height error is as small as 8 nm rms. over 200 mm illuminated length. An extremely sharp gaussian 8 micrometers FWHM wide spot size was obtained by vertically demagnifying the undulator source. It has also been demonstrated that it is possible to bend the mirror to an arbitrary, user-defined, shape; i.e. sinusoidal.