Bimorph

About: Bimorph is a research topic. Over the lifetime, 3339 publications have been published within this topic receiving 51880 citations.

Dimensionally gradient magnetoelectric bimorph structure exhibiting wide frequency and magnetic dc bias operating range

Abstract: We report results on a dimensionally gradient magnetoelectric (ME) sensor that demonstrates high performance over a wide frequency range and a magnetic dc bias operating in the longitudinal-transversal mode. The design of the sensor is based on a piezoelectric bimorph structure and utilizes a laminate configuration with Pb(Zn1/3Nb2/3)0.2(Zr0.5Ti0.5)0.8O3 and Metglas as material layers. The wide-band behavior was characterized by a flat ME response over a wide range of magnetic dc biases corresponding to 60–215 Oe and frequencies corresponding to 7–22 kHz. By using tip mass, the wide-band frequency response was shifted to a lower frequency range of 5–14 kHz. The results show that the operating frequency range of the sensor can be easily shifted by changing the tip mass at the end of the composite.

PZN-PT Single-Crystal Thin Film Monomorph Actuator

Abstract: We report on the use of single-crystal lead zinc niobate-lead titanate films in monomorph actuators. The article responds to the growing interest in solid-solution (1 m x )Pb(Zn 1/3 Nb 2/3 )O 3 - x PbTiO 3 relaxor ferroelectrics based on their large piezoelectric coefficients and their integration into microelectromechanical system. Freestanding films are fabricated by slicing a 7 w m-thick layer off the crystal bulk and assembled into a flexural actuator, thus circumventing polycrystalline deposition techniques. One-micron deflections are observed at 100 V for ∼1 mm-long films. The article discusses the non-uniform electric field distribution profile established in the films and its role in the actuation process.

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.

Micro-Electromechanical Devices Having Variable Capacitors Therein that Compensate for Temperature-Induced Frequency Drift in Acoustic Resonators

Abstract: Micro-electromechanical devices include a temperature-compensation capacitor and a thin-film bulk acoustic resonator having a first terminal electrically coupled to an electrode of the temperature-compensation capacitor. The temperature-compensation capacitor includes a bimorph beam having a first electrode thereon and a second electrode extending opposite the first electrode. This bimorph beam is configured to yield an increase in spacing between the first and second electrodes in response to an increase in temperature of the micro-electromechanical device. This increase in spacing between the first and second electrodes leads to a decrease in capacitance of the temperature-compensation capacitor. Advantageously, this decrease in capacitance can be used to counteract a negative temperature coefficient of frequency associated with the thin-film bulk acoustic resonator, and thereby render the resonant frequency of the micro-electromechanical device more stable in response to temperature fluctuations.

Elastic–plastic modeling of heat-treated bimorph micro-cantilevers

Abstract: This paper models the residual stress distributions within micro-fabricated bimorph cantilevers of varying thickness. A contact model is introduced to calculate the influence of contact on the residual stress following a heat treatment process. An analytical modeling approach is adopted to characterize bimorph cantilevers composed of thin Au films deposited on thick poly-silicon or silicon-dioxide beams. A thermal elastic–plastic finite element model (FEM) is utilized to calculate the residual stress distribution across the cantilever cross-section and to determine the beam tip deflection following heat treatment. The influences of the beam material and thickness on the residual stress distribution and tip deflections are thoroughly investigated. The numerical results indicate that a larger beam thickness leads to a greater residual stress difference at the interface between the beam and the film. The residual stress established in the poly-silicon cantilever is greater than that induced in the silicon-dioxide cantilever. The results confirm the ability of the developed thermal elastic–plastic finite element contact model to predict the residual stress distributions within micro-fabricated cantilever structures with high accuracy. As such, the proposed model makes a valuable contribution to the development of micro-cantilevers for sensor and actuator applications.