Showing papers on "Bimorph published in 1994"

Fabrication of magnetostrictive actuators using rare‐earth (Tb,Sm)‐Fe thin films (invited)

Abstract: A new concept is proposed for the microactuation based upon magnetostriction. Magnetostrictive bimorph cantilever actuators and a traveling machine, composed of the magnetostrictive amorphous Tb‐Fe and Sm‐Fe thin films on a polyimide substrate, were fabricated. These actuators moved without power supply cables. The 3‐mm‐long cantilever actuator exhibited the large deflection above 100 μm in as low a magnetic field as 300 Oe and above 500 μm at resonant frequency in an alternating magnetic field of 300 Oe. Such unique characteristics suggest that magnetostriction is useful as the driving force of the microactuator.

Thermally driven microvalve with buckling behaviour for pneumatic applications

Abstract: The paper presents theoretical and experimental results of a new thermally driven microvalve. In contrast to earlier reported devices with bimorph composition this valve is based on the buckling effect of a heated pure silicon bridge structure. Simulation, fabrication and experimental results are presented. Analytical and finite-element calculations of the thermomechanical behaviour are performed. Prototypes of this first valve design operate with inlet pressures up to 1.0 bar showing flow rates of more than 700 ml/min. The measured switching time is about 15 ms which is extremely low for thermal principles. The power consumption of this valve is between 1 and 4 W.

Proximity sensor utilizing polymer piezoelectric film with protective metal layer

Abstract: An ultrasonic proximity sensor particularly suited for outdoor environments having a transducer including a polymer piezoelectric film (16) bonded to a protective metal layer (18). The transducer is mounted in the sensor housing (30) so that the protective metal layer (18) is exposed to the environment through a window (34) of the sensor housing (30). The transducer can be implemented as an asymmetric bimorph structure, having an electrode bonded to a surface of the polymer piezoelectric film (16) opposite the protective metal layer (18) and between support members (24, 26). Deformation of the polymer piezoelectric film between the protective metal layer (18) and the electrode occurs upon application of a voltage thereto, generating an ultrasonic wave. The transducer can also be used as a receiver, generating an output voltage from the electrode upon impingement of an ultrasonic wave upon the protective metal layer (18). The transducer can also be implemented as a curved length mode transducer including an arcuate shaped support member (28) for supporting the polymer piezoelectric film (16) to be curved between the support members (24, 26). The radius of the curved length mode transducer is selected so that the transducer can be resonant at the resonance frequency of the curved length mode, therefore vibrating at high frequency to generate an ultrasonic wave.

High displacement ceramic metal composite actuators (moonies)

Abstract: The two most common type of piezoelectric actuators are the multilayer actuator with internal electrodes and the cantilevered bimorph actuator[1]. A new type of composite ceramic actuator is the multilayered multistacked moonie (multi-multi moonie). Normal multilayer actuators produce a large generative force, but only a small displacement. Conversely, bimorphs produce large displacements but the forces are very small. The moonie actuator combines the advantages of both, producing a large displacement as well as a reasonably large generative force.

Bimorph adaptive mirrors and curvature sensing.

Abstract: The applicability of wave-front correction by means of a bimorph mirror in conjunction with a curvature sensor is described. We use Zernike polynomials to describe the quality of the atmospheric-turbulence correction analytically. The match is limited by boundary conditions of the mirror and by the discreteness of the electrodes. The correction is limited by coupling of lower- and higher-order Zernike polynomials and necessitates an interfacing computer between the wave-front sensor and the bimorph mirror.

Multibit bimorph magnetic tags using acoustic or magnetic interrogation for identification of an object coupled thereto

Abstract: A tag structure suitable for attachment to an object includes one or more bimorphs comprised of a thin strip of a magnetostrictive material attached to a thicker bar of hard magnetic material. The tag is preferably excited using either magnetic or acoustic fields, tuned to the resonance of the bimorphs. The excitation induces strain in the bimorph which causes mechanical vibrations in the bimorph which are sensed acoustically or magnetically, giving rise to a code. A device for detecting the output of the tag is provided along with a device for decoding the output from the detecting means thereby to identify the object.

The effect of geometry on the characteristics of the moonie transducer and reliability issue

Abstract: The moonie actuator is a versatile performer that fills the gap between the multilayer actuator and the bimorph actuator. This paper describes the effect of geometrical changes in the endcap on the moonie's actuator characteristics. The reliability of multilayer moonie actuators were tested for long term usage and a wide range of temperatures. The effect of cavity dimensions, which are the key parameters for transformation and amplification of lateral motion into axial motion, on the characteristics of the moonie actuator were investigated. Fatigue tests of multilayer moonie actuator were performed under a cyclic electric field of 1 kV/mm with triangular wave form at 100 Hz, up to 107 cycles, at room temperature. Deviations less than p0.1% from the original displacement value were observed. Temperature dependence experiments were performed in the range of -20 to +70dC. Maximum p15% nonpermanent deviations in the displacement from the room temperature value were observed

Characterization of an inchworm prototype motor

Abstract: A new driving principle for an active joint intended for, e.g., a microrobot, has been evaluated. Piezoelectric bimorphs are used as actuator elements, and quasistatic positioning in combination with an inchworm type of repetition produces the rotation. The performance of a macroscopic prototype has been investigated and compared with an analytical model and with finite-element analysis. The agreement between the model and the prototype is good, and it is believed that the characteristics of a microsized active joint can be estimated from the analytical model. The difference in size between the prototype and the proposed micromotor is a factor of 100. A micromotor is expected to have a very high torque-to-volume ratio (3 kN m −2 ). Its power and speed limits are believed to be sufficient for an operational micromotor. Other characteristics that make it well suited for microrobotics are: no gliding contact causing wear, simple design and locked rotor when the voltage is turned off. A possible fabrication process, microassembly, is demonstrated. A bimorph microelement has been successfully bonded to a support on a substrate and the expected behaviour has been verified.

Fabrication and Evaluation of Flexible Microgripper

Abstract: A new concept of a microgripper using Lorentz force actuation and electrothermal bimorph actuation is presented here. Design, theoretical consideration, fabrication process and characterization results are presented. Many free-standing fingers, ranging from 200 µ m to 1000 µ m in length, have been fabricated successfully by the micromachining process. We have observed the low driving voltage performance and the flexible finger motion of the flexible microgripper (FMG) under the microscope. A 210 µ m deflection of a 1000-µm-long finger was obtained at the input voltage of 1 V.

Apparatus and method for spectroscopic measurement as a deflection of a bimorph carrying a sample that is heated by radiation

Abstract: A spectrometer is described with a new intensity detector for electromagnetic radiation. The detector comprises means for detecting the deflection of a cantilever which has a bimetallic/bimorph structure. The deflection is proportional to the absorbed amount of radiation.

Ferroelectric thin films for piezoelectric micromotors

Abstract: The dielectric and piezoelectric properties of lead zirconate titanate (PZT) thin films were investigated to examine its viability for application to a new family of flexure-wave piezoelectric micromotors, characterized by low speed and high torque. Stored energy densities higher than the air-gap electrostatic actuators accrue from high relative dielectric permittivity (1300) and breakdown strength (1 MV/cm) of the films. The piezoelectric longitudinal and transverse strain coefficients were measured by a nonresonance technique through a modified Mach-Zehnder laser interferometer; at a dc bias of 75 k V/cm, d33 was measured to be 220 pC/N; evaluation of the film as a bimorph yielded a value of —88 pC/N for d31 at 200 kV/cm ac field. The electromechanical coupling factors calculated thereupon were k33 = 0.49, k31 = 0.22, and kp = 0.37. The development of the piezoelectric ultrasonic micromotors from the PZT thin films, and the architecture of the stator structures are described. Nonoptimized prototype micr...

Anomalous behaviour of bimorph consisting of conducting polymer gel in electrochemical doping

Abstract: Summary form only given. Recently we have found the gel characteristics in the lightly cross-liked conducting polymers such as poly(3-alkylthiophene). The volume instability of conducting polymer gel has been found by changing solvent composition and temperature and also upon doping. We have also indicated the possibility of actuator using conducting polymer gel. Indeed the bimorph consisting of poly(3-alkylthiophene) gel and polypyrrole has been provided and driven by electrochemical doping. The bend of the bimorph could be controlled by the doping potential and therefore the dopant concentration. The response time changed by doping potential, electrolyte concentration and the size of bimorph. Anomalous behaviour in the response were observed for excess doping level. The origin of this unique behaviour was discussed by taking the role of the dopant in the gel into consideration.

Cooled bimorph adaptive mirrors for laser optics

Abstract: Cooled bimorph adaptive copper and molybdenum mirrors are proposed for the compensation of large-scale optical aberrations in laser systems with an output power up to 15 kW. An investigation is reported of the characteristics of the developed and fabricated cooled bimorph mirrors. The experimental results are compared with those obtained by computer modelling. Promising designs of bimorph adaptive mirrors are proposed and discussed.

Piezo-electric actuator and head actuator

Abstract: PURPOSE:To obtain a bimorph type piezo-electric actuator with cantilever structure having large deformation and high resonance frequency and a head actuator by solving mutually contradictory relation for improving both of deformation and resonance frequency. CONSTITUTION:In a bimorph element (piezo-electric actuator) 104 obtained by mutually sticking the 1st and 2nd piezo-electric substances 101, 102 through an elastic shim material 103, the 1st and 2nd substances 101, 102 are stuck to the material 103 longer than the length of the substances 101, 102 at least on the fixed end side of the element 104. The fixing part 103a of the material 103 which is a longer part than the length of the substances 101, 102 is completely fixed by a fixing board 105 and a part of the substances 101, 102 is supported and fixed by an elastic member 108.

Method and apparatus for increasing bimorph displacement range

Abstract: A bimorph apparatus having an extended range of displacement is disclosed herein. The bimorph apparatus is typical in that it includes a bimorph having a conductive vane (7) sandwiched between first (5) and second (6) piezoelectric layers, free for movement in response to electrical signals applied thereto. The bimorph includes a driver circuit for developing a first potential drop across the first layer which induces contraction thereof. In addition, however, a second driver circuit operates to develop a second potential drop different from the first potential drop across the second layer contemporaneous with development of the first potential drop, thereby inducing expansion of the second layer. In this way simultaneous contraction and expansion of the first and second layers results in extended displacement of the free portion of the bimorph in a first direction. The second driver circuit may be adapted to apply a third electrical signal to the second layer, and the first driver circuit implemented to apply a fourth electrical signal to the first layer simultaneously with application of the third signal to the second layer. In this manner extended movement of the free portion of the bimorph is induced in the opposite direction or some other second direction.

Positioning control method, facing method, tunneling microscope using it, and recording/reproducing device

Abstract: PURPOSE:To easily measure the distance between the sample surface and a piezoelectric element by changing the cantilever type piezoelectric element at its natural frequency, and changing the admittance of the piezoelectric element. CONSTITUTION:A cantilever type piezoelectric element 1 formed with a Si substrate 2 and a sample 7 are arranged, and the element 1 is fixed to another expanding piezoelectric element 3. The bimorph type element 1 is driven by an AC power source 5 to make bending movement. The admittance of the element 1 can be measured by a voltmeter 6. The distance between the element 3 and the element 1 can be controlled by a variable DC power source 4. When voltage is applied to the element 3 from the power source 4 and the tip of the element 1 is brought into contact with the sample 7, the natural frequency is changed, and the admittance is changed. The element 3 is adjusted so that the element 1 is kept in no contact with the surface of the sample 7, then the bending movement of the piezoelectric element 1 is performed at the natural frequency by the power source 5. If the applied voltage when the element 1 is brought into contact with the sample 7 and the displacement quantity at the natural frequency are found, the distance between the stationary point at the tip of the element 1 and the surface of the sample 7 can be measured.

Structure-borne sound detector for an intruder alarm system

Abstract: The detector contains a structure-borne sound microphone connected to an electronic evaluation unit with a piezoelectric sensor (18) for structure-borne sound vibrations. This sensor has a vibrating bar (28), which is attached by means of hybrid technology to a carrier (27). The vibrating bar (28) is formed by a bimorph element and the carrier by an electrically conductive ceramic wafer.

Laser ablation deposition as a preparation method for sensor materials

Abstract: In the development of new materials for sensors, laser ablation deposition (LAD) offers a relatively easy technique to realise complicated material compositions and multilayer structures. In this paper, LAD of three different thin films for sensor and actuator materials was carried out using a Q-switched ND:YAG laser and an XeCl excimer laser. CuInSe 2 (CIS) and Cu(In, Ga)Se 2 (CIGS) are well-established as exceptionally efficient semiconductors with potential applications in the fields of solar cells, infrared radiation monitors and fibre optic infrared detectors. CIS and CIGS thin films were deposited by an in situ process on fused silica and single crystal silicon substrates. The composition of the target material was largely maintained in the thin films. Lead zirconium titanate (PZT) materials are widely used in sensor and actuator applications. Laser ablation has been used to produce piezoelectric thin films for use in a low voltage cantilever bimorph actuator structure. Nd-doped PZT films were deposited on to Ag-coated oxidised silicon substrates. Displacements in the order of microns were obtained from a 15 mm long element. Diamond-like carbon thin films also have potential in sensor applications. By varying the peak power density of the laser beam and the deposition temperature, it was found to be possible to tailor the electrical and optical properties of the deposited films between the extremes of diamond-like and graphite-like carbon.

Analysis of Sensitivity of Accelerometer Using Multilayer Piezoelectric Ceramics

Abstract: We have investigated the application multilayer piezoelectric ceramics (MPC) to accelerometers to sense acceleration in the low-frequency range. A method of analysis applying the piesoelectric fundamental equation of bimorph to each layer of the MPC and summing them up has been studied. The propriety of this method was demonstrated by comparing calculated and experimental results.

Apparatus and method for spectroscopic measurements

Abstract: A spectrometer is described with a new intensity detector for electromagnetic radiation. The detector comprises means for detecting the deflection of a cantilever which has a bimetallic/bimorph structure. The deflection is proportional to the absorbed amount of radiation.

Underwater Performance of Flexible Microgripper and Fine Particle Manipulation

Abstract: Underwater performance of the microfabricated flexible microgripper (FMG) using Lorentz force actuation and electrothermal bimorph actuation is presented here. The Lorentz force actuation was a primary factor of the actuation for the underwater operation of FMG. We have manipulated the polystyrene fine particles successfully by using the FMG in water.

Miniature Thermoacoustic Refrigerator.

Abstract: : A miniature thermoacoustic refrigerator was developed for cooling electronic components. The refrigerator is driven at 5,000 Hz by a piezoelectric driver and it consists of an acoustic resonator, a stack, and copper heat exchangers. The working fluid is pressurized helium gas between 10 to 20 atmospheres. Sound was produced with different piezoelectric drivers, a monomorph, a bimorph, and Tonpilz driver to achieve the highest intensity possible. Since the operating frequency is high, the refrigerator is compact, being about 10 cm long. Temperature differences of 12 deg C across the stack were achieved at sound levels of l60dB. The performance of the refrigerator scaled with frequency according to existing models of thermoacoustic heat engines.

Piezoelectric actuator and driving method therefor

Abstract: PURPOSE:To suppress primary and secondary resonance peaks to low and to improve vibrating characteristics of a piezoelectric actuator by separating a control electrode of a bimorph type piezoelectric element of the actuator into a main electrode, an auxiliary electrode and a sensor electrode. CONSTITUTION:An electrode 41 of a bimorph type piezoelectric element 31 is formed of a pair of main electrode 43 and a subelectrode 45 and a sensor electrode 47 independent from each other. The electrode 43 is relatively narrowed at parts corresponding to antinodes of primary and secondary resonances to be formed with narrowed parts 43a. On the other hand, the electrode 45 is, on the contrary, widened in an electrode pattern at parts corresponding to the antinodes of primary and secondary resonances to be formed with wide parts 45a. The electrode 47 is formed longitudinally in a uniform width to detect generation of a resonance peak. The electrode 45 is driven in a reverse phase to the electrode 43 with frequency components of the primary and secondary resonances from the electrode 45 as drive signals of the electrode 45 by using the electrode 45 formed with the wide parts 45a at the parts corresponding to the antinodes of the resonances to suppress the resonance peak to a low value.

Performance improvement of optical actuator by double sides irradiation

Abstract: As a microactuator, we focus on a bimorph type piezoelectric actuator which has relatively large displacement. We made it and improved its response characteristics by irradiating the ultraviolet rays from the both sides of the actuator. Time to change the bending direction of this actuator is extremely improved compared with the previous single side irradiation. We proposed the PWM control for the actuator to change the strength of the ultraviolet rays and presented the model of this control system. Experimental results show the control system performance is fairly improved. >

Photo-acoustic devices using (Pb,La)(Zr,Ti)O/sub 3/ ceramics

Abstract: Photostriction in ferroelectrics arises from a superposition of photovoltaic and inverse piezoelectric effects. This phenomenon provides promise for photo-acoustic devices, when the response has been sufficiently improved. In this paper, B-site donor doping was investigated in (Pb,La)(Zr,Ti)O/sub 3/ based ceramics with the aim of improving the response speed. Using a PLZT bimorph configuration, a photoacoustic device was fabricated, and the fundamental mechanical resonance was observed under intermittent illumination of purple-color light, having neither electric lead wires nor electric circuit.

Tweezers for fine object

Abstract: PURPOSE:To vary a displacement amount and displacement speed of a tweezers head end part by optionally varying a voltage waveform applied to a piezoelectric member. CONSTITUTION:When switches 31 and 34 are switched on, a command signal to catch at low speed is given to a control circuit 21 through an interface circuit 22, and the control circuit 21 gives a slowly rising waveform signal to the interface circuit 22. The interface circuit 22 gives voltage in accordance with its waveform to a bimorph element consisting of piezoelectric elements 2, 3 and a shim material 4 and displaces it in accordance with its voltage waveform. By its displacement, an attachment 7 holds a fine object 15 between tweezers head end parts 8. When the switches 31, 33 are switched off, the voltage applied to the bimorph element is slowly lowered, and the tweezers attachment 7 returns to its original position. When a switch 32 is switched on, the bimorph element oscillates and the head end parts oscillate, and the fine object 15 leaves a pair of tweezers.

Resonance and antiresonance of symmetric cantilevered piezoelectric flexors

Abstract: The resonances of dynamically excited symmetric piezoelectric bimorphs have been determined from the equations of state. Under the effect of sinusoidal stimuli: an electrode voltage V, a moment exerted at the tip M, a force exerted perpendicular to the plane of the bimorph also applied at the tip F, and a uniformly applied pressure p, they respond with a sinusoidal electrode charge Q, tip rotation a, tip deflection d, and volume displacement n. All of the former are related to all of the latter through a dynamic admittance matrix B. We have found the antiresonance frequency of the capacitance C, while also antiresonance in off-diagonal elements is determined. The latter indicate that at these frequencies the bimorph does not work as an actuator or sensor in the particular domain of the off-diagonal. The mode shape at these antiresonance frequencies has been determined. The antiresonance of b14 determines that for this frequency the tip has deflection but no rotation, while the antiresonance of b24 indicates that the tip has rotation but no deflection. No antiresonance in the volume displacement is found, indicating that the bimorph is a pressure converter (microphone) at all frequencies

Piezoelectric displacement device

Abstract: PURPOSE:To provide a title device which can obtain a suitable generation force and a large displacement by high-speed drive with regard to this device utilizing displacement and force generated by deforming a piezoelectric body. CONSTITUTION:A bimorph displacement piece 1, 1 is formed by laminating a metal base 5 with a piezoelectric body 4 having polarization regions 2a, 2b, 2c... or electrodes 3a, 3b, 3c... divided into a plurality in a longitudinal direction. After many displacement pieces 1, 1 are so piled up that apexes of deflection generated when these displacement pieces 1,1 deflect may overlap, they are depressed in the pileup direction by means of a restoration force such as of a belville spring 13 or lining of a synthetic resin to constitute an integral displacement device. This constitution causes bimorph displacement pieces 1, 1 to be displaced by an amount of a multiplied number of pileups. Further, apexes of deflection with many curvatures are made to serve as points of output support, so that a large generation force can be obtained.

Bimorph deformable mirror design

Abstract: We describe the applicability of wave front correction by using a bimorph mirror in conjunction with a curvature sensor. We use Zernike polynomials to describe analytically the quality of the correction for atmospheric turbulence. The match is limited by boundary conditions of the mirror and by the discreteness of the electrodes. The correction is limited by coupling of lower and higher order Zernike polynomials and necessitates an interfacing computer between the wave front sensor and the bimorph mirror.