Showing papers on "Interdigital transducer published in 2008"

Flow induced by acoustic streaming on surface-acoustic-wave devices and its application in biofouling removal: a computational study and comparisons to experiment.

Abstract: All transducers used in biological sensing suffer from fouling resulting from nonspecific binding of protein molecules to the device surface. The acoustic-streaming phenomenon, which results from the fluid motion induced by high-intensity sound waves, can be used to remove these nonspecifically bound proteins to allow more accurate determinations and reuse of these devices. We present a computational and experimental study of the acoustic-streaming phenomenon induced by surface acoustic waves.A coupled-field fluid-structure interaction (FSI) model of a surface-acoustic-wave (SAW) device based on a micrometer-sized piezoelectric substrate (YZ-LiNbO3) in contact with a liquid loading was developed to study the surface-acoustic-wave interaction with fluid loading. The fluid domain was modeled using the Navier-Stokes equation; the arbitrary Lagrangian-Eulerian approach was employed to handle the mesh distortions arising from the motion of the solid substrate. The fluid-solid coupling was established by maintaining stress and displacement continuity at the fluid-structure interface. A transient analysis was carried out by applying a time-varying voltage to the transmitter interdigital transducer (IDT) fingers. Simulation results predict strong coupling of ultrasonic surface waves on the piezoelectric substrate with the thin liquid layer causing wave mode conversion from Rayleigh to leaky SAWs, which leads to acoustic streaming. The transient solutions generated from the FSI model were utilized to predict trends in acoustic-streaming velocity for varying design parameters such as voltage intensity, device frequency, fluid viscosity, and density. The induced streaming velocities typically vary from 1 mum/s to 1 cm/s, with the exact values dictated by the device operating conditions as well as fluid properties. Additionally, the model predictions were utilized to compute the various interaction forces involved and thereby identify the possible mechanisms for removal of nonspecifically bound proteins. Our study indicates that the SAW body force overcomes the adhesive forces of the fouling proteins to the device surface and the fluid-induced drag and lift forces prevent their reattachment. The streaming velocity fields computed using the finite-element model in conjunction with the proposed mechanism were used to identify the conditions leading to improved removal efficiency. Predictions of the model are in good agreement with those of simple analytical theories as well as the experimentally observed trends of nonspecific protein removal in typical SAW biosensing operations.

Miniature Surface Acoustic Wave Duplexer Using SiO2/Al/LiNbO3 Structure for Wide-Band Code-Division Multiple-Access System

Abstract: In this paper, we describe the development of a miniature surface acoustic wave (SAW) duplexer for Band I in the standard of the Third-Generation Partnership Project (3GPP) at a 2 GHz band. We employed a shear-horizontal SAW on a SiO2 overlay/thick Al electrode/5°YX-LiNbO3 structure, which offers a high electromechanical coupling coefficient (K2) as well as a small temperature coefficient of frequency (TCF). This feature is crucial for the realization of a wide duplex gap between the transmitting and receiving bands in the Band I specification. We investigated experimentally that the spurious response caused by the Rayleigh-mode could effectively be suppressed by controlling the cross-sectional shape of a SiO2 overlay on interdigital transducer (IDT) electrodes. In addition, the result also showed how this spurious response depends on IDT design parameters, i.e., electrode pitch and metallization ratio. The developed SAW duplexer was installed in a 2.5×2.0 mm2 package, and exhibited a low insertion loss, a high out-of-band rejection and a small TCF.

Polydimethylsiloxane-LiNbO3 surface acoustic wave micropump devices for fluid control into microchannels.

Abstract: This paper presents prototypical microfluidic devices made by hybrid microchannels based on piezoelectric LiNbO3 and polydimethylsiloxane. This system enables withdrawing micropumping by acoustic radiation in microchannels. The withdrawing configuration, integrated on chip, is here quantitatively investigated for the first time, and found to be related to the formation and coalescence dynamics of droplets within the microchannel, primed by surface acoustic waves. The growth dynamics of droplets is governed by the water diffusion on LiNbO3, determining the advancement of the fluid front. Observed velocities are up to 2.6 mm s−1 for 30 dBm signals applied to the interdigital transducer, corresponding to tens of nl s−1, and the micropumping dynamics is described by a model taking into account an acoustic power exponentially decaying upon travelling along the microchannel. This straighforward and flexible micropumping approach is particularly promising for the withdrawing of liquids in lab-on-chip devices performing cycling transport of fluids and biochemical reactions.

Subwavelength focusing of surface acoustic waves generated by an annular interdigital transducer

Abstract: We propose and demonstrate experimentally the concept of the annular interdigital transducer that focuses acoustic waves on the surface of a piezoelectric material to a single, diffraction-limited spot. The shape of the transducing fingers follows the wave surface. Experiments conducted on lithium niobate substrates evidence that the generated surface waves converge to the center of the transducer, producing a spot that shows a large concentration of acoustic energy. This concept is of practical significance to design new intense microacoustic sources, for instance for enhanced acousto-optical interactions.

Development of a Shear Horizontal Surface Acoustic Wave Sensor System for Liquids with a Floating Electrode Unidirectional Transducer

Abstract: The development of sensors using surface acoustic wave (SAW) devices has been attracting attention A shear horizontal SAW (SH-SAW) sensor can detect the properties and chemical reactions in liquids To realize practical applications of the SAW sensor, it is necessary to discuss its properties In this paper, SH-SAW sensors with a floating electrode unidirectional transducer (FEUDT) or an interdigital transducer (IDT) are compared and the insertion loss and phase characteristics are measured Also, the phase shift between sample and reference liquids is evaluated The results indicate that the SH-SAW sensor with the FEUDT is suitable for liquid measurements The SH-SAW sensor with the FEUDT is then mounted in a newly developed SH-SAW sensing system The system configuration is the same as that of a vector voltmeter measurement system However, circuits have been developed that reduce its size Using this system, several liquids are measured The obtained results agree well with the theoretical values

Design, fabrication, and characterization of single-element interdigital transducers for NDT applications

Abstract: Single-element interdigital transducers (IDTs) are designed, fabricated, and characterized as a complimentary sensor approach for traditional ultrasonic transducers used in nondestructive testing (NDT). The frequency of interest is in the lower megahertz range, 2–10 MHz. In this paper, a simple five-finger paired IDT is described, where laser micro-machining techniques were used to shape the electrode patterns for an IDT resonance frequency of ∼3 MHz. Detailed characterization of the Rayleigh surface waves generated by the IDT is performed using a scanning laser interferometry system. Wave properties such as beam profile, beam divergence, energy decay, frequency response, and phase dependence are reported.

Three operation modes of lateral-field-excited piezoelectric devices

Abstract: Through theoretical calculations and experiments, three operation modes of lateral-field-excited piezoelectric bulk acoustic wave devices, which are referred to as the pure lateral field excitation (LFE), quasi-LFE, and pseudo-LFE modes, are presented Several 4–6 MHz LFE devices with similar geometry using lithium niobate, lithium tantalate, and AT-cut quartz crystals are fabricated and tested in air and de-ionized water, respectively The experimental results are in well agreement with the theoretical calculations

Rayleigh surface acoustic wave modes of interdigital transducer/(100) AlN/(111) diamond

Abstract: In this research, Rayleigh surface acoustic wave (SAW) modes of interdigital transducer (IDT)/(100) AlN/(111) diamond were theoretically analyzed and exhibited some excellent acoustic properties. Those Rayleigh SAW modes have smaller film thickness ratios (h/λ), higher phase velocities, and larger electromechanical coupling coefficients (K2) than the ones of IDT/(002) AlN/(111) diamond. Especially for mode 1, the phase velocity is 10 474 m/s, the K2 is 2.31%, and the film thickness ratio (h/λ) is 0.3. The research results exhibit that IDT/(100) AlN/(111) diamond has some excellent properties and provides a predictable and theoretical basis for further application in high velocity SAW devices.

GHz frequency ZnO/Si SAW device

Abstract: The demand for high-frequency low-loss filters generates intensive research on innovative wave guide solutions. In this work, a GHz SAW device based on a ZnO/Si structure was fabricated using classical UV photolithography. The thickness of the piezoelectric thin film was optimized and a specific interdigital transducer structure was used to generate third and fifth harmonic guided waves at 2.5 GHz and 3.5 GHz, respectively, with an aluminum strip larger than 1 micrometer. Different modes have been measured and theoretically identified thanks to an advanced finite-element/boundary-element- based model. Good agreement is found between theory and experiments. The high-frequency modes have been fully characterized, allowing for accurate design of SAW devices exploiting such modes.

Gigahertz surface acoustic wave generation on ZnO thin films deposited by radio frequency magnetron sputtering on III-V semiconductor substrates

Abstract: The authors demonstrate 1.6GHz surface acoustic wave (SAW) generation using interdigital transducers patterned by e-beam lithography on a thin ZnO piezoelectric film deposited on an InP substrate. The highly oriented, dense, and fine-grain ZnO film with high resistivity was deposited by radio frequency magnetron sputtering and was characterized by x-ray diffraction, scanning electron microscopy, atomic force microscopy, and a four-point probe station. The acoustic wavelength of the 1.6GHz SAW generated by exciting the interdigital transducer on ZnO∕InP with a microwave signal is 1.6μm. This SAW filter device could be monolithically integrated with optoelectronic devices, opening new opportunities to use SAWs for applications such as gigahertz-frequency filters on optoelectronic devices and novel widely tunable quantum cascade lasers.

Propagation characteristics of shear horizontal surface acoustic waves in (11 2 0) ZnO film/silica glass substrate structures

Abstract: This paper presents the propagation characteristics of the shear horizontal surface acoustic wave (SH-SAW) in ZnO (0deg, 90deg, psi) (11 2macr 0) textured ZnO films. ZnO (0deg, 90deg, 0deg) film/interdigital transducer (IDT) electrode/silica glass substrate structures were fabricated by RF magnetron sputtering. Experimental results demonstrate that SH-SAW was clearly excited in these structures. We also theoretically estimated the electromechanical coupling coefficient K2 in the ZnO (0deg, 90deg, psi) film/silica glass substrate structure. The theoretical results show that the IDT electrode/ZnO (0deg, 90deg, 55deg) film/silica glass substrate structure had a relatively high K2 value of 3.4%. Moreover, the shear horizontal displacement component of the SH-SAW in this structure is much larger than the transverse and longitudinal displacement components. This structure could be used in SH-SAW sensors for evaluating the electrical properties of liquids.

Sensitivity improvement of wireless pressure sensor by incorporating a saw reflective delay line

Abstract: this paper presents a wireless surface acoustic wave (SAW) pressure sensor on 41 o YX LiNbO3 for tire pressure monitoring system (TPMS) application, in which a reflective delay line composed of an interdigital transducer (IDT) and several reflectors was used as the sensor element. Using the coupling of modes (COM), the SAW reflective delay line was simulated, and the optimal design parameters were determined. The fabricated 2.4GHz SAW sensor was wirelessly characterized by the network analyzer. Sharp reflection peaks, few spurious signals, and relatively high signal-to-noise (S/N) ratio were observed. High sensitivity of 2.9 deg/kPa and good linearity were observed.

Sonic surface wave microfluid driver for chip lab and manufacturing method thereof

Abstract: The invention relates to a surface acoustic wave micro-fluidic drive for a chip lab pertaining to the technical field of micro-electro-mechanical system and a manufacture method thereof. The drive of the invention comprises a base, an interdigital transducer and a micro-fluidic channel, wherein the base is a 128 degrees Y-X lithium niobate single crystal, an IDT formed by the intercrossed interdigital transducer is on the base, and the micro-fluidic channel is integrated with the base. The invention uses floating electrode type unidirectional transducer structure design to realize unidirectional driving of the micro fluid, the procedure of the method is: (1) processing of the floating electrode type unidirectional transducer; (2) micro-processing of the micro-fluidic channel; (3) integration of the base and the micro-fluidic channel. The whole processing procedure of the invention can be completely made by means of semiconductor material based micro-manufacture method, having characteristics of no moving micro-parts itself and no damage to the fluid dielectric etc., the processing has advantages of reliable operation, stabilization and long service life.

Coupling coefficient determination based on simulation and experiment for ST-Cut quartz saw delay-line response

Abstract: This paper used the theoretical calculation to simulate the response of surface acoustic wave (SAW) delay-line on quartz substrate and then compared to the experimental results. The coupling coefficients affected by operation frequency as well as aperture length were built up by experimental data analysis. Based on the experimental values of these two parameters, the device-coupling coefficient was defined. This method is new and we has not found in other document. In addition, it improves the simulation results and helps the analysis process more comprehensive. This study developed ST-cut quartz SAW delay-lines with gold inter-digital transducer (IDT) operating at 39.5 and 78.9 MHz corresponding to 80 and 40 μm of the wavelength. The differences of aperture length in IDT designs were investigated to help understand the effects of this parameter on SAW sensor response. The maximum error of operating frequency is 1%; of insertion loss is 4.25 and 3.13% for bandwidth. The larger of the insertion loss error is expected owing to the result of mathematical approximation and the quality of quartz substrate. The simulation results agree with the experimental results shows that the simulation method can apply to quartz-based SAW delay-line as well as for other material based SAW delay-line applications. The results help understand more about the parameters which effect the insertion loss, operating frequency and bandwidth. It should be very useful for IDT design in specific, SAW sensor and SAW filter design in general.

High-frequency shear-horizontal surface acoustic wave sensor

Abstract: A Love wave sensor uses a single-phase unidirectional interdigital transducer (IDT) on a piezoelectric substrate for leaky surface acoustic wave generation. The IDT design minimizes propagation losses, bulk wave interferences, provides a highly linear phase response, and eliminates the need for impedance matching. As an example, a high frequency (˜300-400 MHz) surface acoustic wave (SAW) transducer enables efficient excitation of shear-horizontal waves on 36° Y-cut lithium tantalate (LTO) giving a highly linear phase response (2.8° P-P). The sensor has the ability to detect at the pg/mm 2 level and can perform multi-analyte detection in real-time. The sensor can be used for rapid autonomous detection of pathogenic microorganisms and bioagents by field deployable platforms.

Surface acoustic wave filter, boundary acoustic wave filter, and antenna duplexer using same

Abstract: A surface acoustic wave filter includes a piezoelectric substrate including lithium niobate, a series resonator including a first interdigital transducer electrode provided on the piezoelectric substrate, and a parallel resonator including a second interdigital transducer electrode provided on the piezoelectric substrate and being electrically connected to the series resonator. An apodized weighting factor of the first interdigital transducer electrode is smaller than an apodized weighting factor of the second interdigital transducer electrode. This surface acoustic wave filter has a small loss.

Sound surface wave sensor chip and its making method

Abstract: The invention discloses a surface acoustic wave sensor chip and a manufacturing method thereof. The invention comprises a piezoelectric substrate which is provided with an Au layer. The chip comprises an interdigital transducer and a film forming area, among which, the interdigital transducer portion is provided with a film forming masking layer, and the Au layer of the film forming area is provided with a sensitive film. The sensitive film is a polymer film which can adsorb and desorb specific gas. When a chip is made, the film forming masking layer is first covered on the non film forming area, and before a chemical sensitive film is formed on the film forming area, the non film forming area is masked with the film forming masking layer. The invention can well solve the problems of loose masking, bad consistency, chip contamination during the sensitive film forming process. Furthermore, the process is simple, efficient, stable and reliable, and the influence to the electrical property of the chip is little.

Surface acoustic wave based sensor apparatus and method utilizing semi-synchronous saw resonators

Abstract: A SAW based sensor apparatus utilizing semi-synchronous SAW resonator having a single resonance at Bragg frequency with very high quality factor is disclosed. The semi-synchronous SAW resonator includes at least one inter-digital transducer, which generates and receives surface acoustic wave and a number of grating reflectors, which reflect the surface acoustic wave and generate a standing wave between the reflectors, The interdigital transducer and the grating reflectors can be fabricated on a substrate (e.g., quartz) by photolithographic process. The resonance condition is independent of transducer directivity and reflection coefficient per finger. Such a SAW based sensor apparatus having three semi-synchronous SAW resonators can be utilized for measuring pressure and temperature for a wireless tire-pressure monitoring system.

Hydrogen Gas Sensor Using Good Characteristics of Lamb Wave

Abstract: A Lamb wave exists in high-density states when its wavelength is comparable to substrate thickness. It propagates through the boundaries of the upper and lower surfaces in many modes. In this paper, proposes a hydrogen gas sensor fabricated using the good characteristics of a Lamb wave. The film thickness of a sensitive membrane and Lamb wave mode dependence are defined by theoretical analysis and experiment. A Y-cut, Z-direction propagation LiNbO3 substrate (91-µm-thick, double-sided polishing) was used as a piezoelectric substrate of a device. An interdigital transducer with a wavelength of 100 µm was installed on the surface of the device; a sensitive membrane was attached on to the rear face using an RF sputtering process. A palladium silver alloy was used as the sensitive membrane. The maximum frequency shift is 9.21 ppm at hydrogen concentration 9.1%.

Wireless passive sonic surface wave mixed parameter measuring sensor and parameters analysis method

Abstract: The invention discloses a sound surface wave sensor which has a simple structure and can detect two physical quantities (such as temperature, pressure and strain, etc.) at the same time, as well as a method used in the parametric analysis of the physical quantity feedback signal detected by the sensor by means of the sound surface wave delay line theory. Compared with the prior sensor based on the same principle, the invention overcomes the disadvantages that the prior sound surface wave sensor can only detect a single physical quantity, or the prior sensor needs to adopt a relatively complex structure in order to detect two physical quantities. The invention can detect two physical quantities at the same time through making full use of the characteristic that the sound surface wave energy signal generated by an interdigital transducer can be transmitted in two directions at the same time. The sound surface wave sensor, which has a simple structure, has the outstanding characteristics of easy batch production and processing, a small volume, light weight and zero aging rate, etc.; theoretical analysis verifies that the sensor can ensure that the feedback signal of the two measured physical quantities can generate independent detection signal through data processing by means of a certain method.

One-Millimeter Diameter Harmonic Ball Surface Acoustic Wave Gas Sensor with Temperature Compensation by Itself

Abstract: A newly designed 1-mm diameter harmonic ball surface acoustic wave (SAW) gas sensor has a double-electrode interdigital transducer (IDT) for driving multiple frequencies. The fundamental frequency is 80 MHz. The difference in delay time between a fundamental frequency component and a high harmonics was used to compensate temperature drift. A temperature coefficient of about 0.1 ppm/°C was obtained after compensation.

Application of slanted finger interdigital transducer surface acoustic wave devices to ultraviolet array photodetectors

Abstract: An ultraviolet array photodetector is developed by the application of a LiNbO3-based slanted finger interdigital transducer (SFIT) and several ZnO optically active areas. This array photodetector can obtain ultraviolet light intensities within a single measurement. In this analysis, the acoustoelectric interaction between the photogenerated carriers in several active areas and a SFIT surface acoustic wave device is simulated. In the experiment, the photodetector with one to three optically active areas are fabricated. Ultraviolet light with a wavelength of 380 nm and an intensity of 65 μW cm−2 is detectable from the photodetector developed in this study. The minimum size of the optically active areas is 0.04 mm2 that can provide good spatial resolution. The ultraviolet array photodetector is capable of measuring a distributed light field.

Design and Fabrication of Passive Wireless SAW Sensor for Pressure Measurement

Abstract: This paper mainly presents the design and fabrication of a TDMA (time division multiple access) passive wireless pressure sensor using 2.45 GHz surface acoustic wave (SAW) delay lines. The SAW pressure sensor consists of two LiNbO3 substrates. The first layer is a pressure-detective thin substrate, on which an interdigital transducer (IDT) and reflectors are fabricated. The second layer is a support substrate, in which a reference pressure cavity is etched. These two substrates are directly bonded. The pressure measurement was successfully demonstrated in a pressure range of 20∼280 kPa with good repeatability. In addition, the influence of a tire on the wireless interrogation of the sensor was investigated. Automobile tires have little negative influence on wireless communication, at least if they do not rotate.

Method for manufacturing surface acoustic wave device

Abstract: A method for manufacturing a surface acoustic wave device comprises depositing a detecting material layer on a substrate, forming a predetermined pattern on the detecting material layer using a nanoimprint method to obtain a detecting film with a predetermined pattern formed thereon, and forming an input interdigital transducer and an output interdigital transducer on two opposite sides of the detecting material layer on the substrate, thus obtaining a surface acoustic wave device comprising the detecting film.

Interaction of Rayleigh Waves Induced by Interdigital Transducer with Fatigue Crack

Abstract: Compared to bulk waves, Rayleigh waves can propagate much longer distances with lower signal attenuation levels, which are nominally pro portional to r / 1 for a given frequency (r=distance). In addition to the small attenuation, Ra yleigh waves are also non-dispersive and sensitive to surface-breaking defects. The surface penetra tion depth of Rayleigh waves is also approximately one wavelength, which can be beneficial for many NDT applications. However, one major drawback of using Rayleigh waves for nondestructive testing has been the difficulty of generating Rayleigh waves, where the most commonly used method involves the combination of a plastic wedge and a conventional longitudinal mode trans ducer. Unfortunately, a number of wedges with different angles are needed to generate Rayl eigh waves in different materials or at different operating frequencies to satisfy the critical Rayleigh launch angle requirement. In this study, instead of using wedge transducers, we have designed, fab ricated, and tested narrow-band Interdigital Transducers (IDTs), where precision elect rode patterns were etched on piezoelectric ceramic substrate materials using micro laser machining t echniques. These IDTs can be directly applied to the surface of test specimens to generate Rayle igh waves in MHz range. A laser interferometry system was used to characterize the I DT sensors, where a well-defined and directional Gaussian beam profile was observed. Inves tigations were also made for Rayleigh waves interacting with fatigue cracks in aircraft qualifi ed metallic alloys. It was observed that some of the Rayleigh wave energy can propagate through a tight crack at both normal and oblique incidence.

Fabrication of the cyclical fluid channel using the surface acoustic wave actuator and continuous fluid pumping in the cyclical fluid channel

Abstract: A surface acoustic wave (SAW) device has been reported as a micro fluid device such as a pump of a water droplet so far (Renaudin et al. in μTAS, pp 599–601, 2004, 1:551–553, 2005; Sritharan et al. in Appl Phys Lett 88:054102, 2006; Wixforth in Anal Bioanal Chem 379:982–991, 2004; Yamamoto et al. in μTAS, pp 1072–1074, 2005). The SAW device is an interdigital transducer (IDT) fabricated on the piezoelectric substrate only. IDTs are advantageous in terms of integration, miniaturization, free position setting on the substrate and simple fabrication process because of their simple structure. Therefore, the SAW device is easy to apply to integrated chemical system such as lab-on-a-chip. The SAW drives the liquid homogenously by the transmission of surface vibrations of the substrate. Thus, both ends of the channel for pressure loading are not necessary to pump the liquid by using the SAW. The SAW can pump the liquid in both of a closed channel and an opened channel, although continuous flow pumping using an external pump is difficult for no loading pressure in the closed fluid channel. In this paper, we proposed and fabricated the micro fluid devices combined cyclical fluid channel and SAW actuator for liquid pumping. This device is fabricated on a piezoelectric substrate (LiNbO3) with UV photolithography and wet etching. Structure material of cyclical fluid channel is epoxy photoresist SU-8 100. Then, it is demonstrated to continuous flow pumping and reciprocal flow pumping in the channel. As a result of optimization of a SAW pump’s structural parameter, 32.5, 71.3 and 108.0 mm/s are achieved in the 500, 1,000 and 2,000 μm channel width as a maximum flow velocity.

Analysis of the acoustoelectric behavior of microwave frequency, temperature-compensated AlN-based multilayer coupling configurations

Abstract: Piezoelectric AlN films, 1.3–6.2 μm thick, have been grown on bare and metallized Al2O3(0001) substrates by reactive radio-frequency-sputtering technique at 180 °C. The films were uniform, stress-free, highly c-axis oriented normal to the surface, and extremely adhesive to the substrates. Surface acoustic wave (SAW) delay lines, showing harmonic modes with operating frequencies up to about 2.44 GHz, were obtained just using conventional optical lithography at 7.5 μm linewidth resolution. Four interdigital transducer (IDT)/counter electrode configurations were obtained locating the IDTs either on the AlN free surface or at the Al2O3/AlN interface, with and without an Al thin metal film opposite the IDTs. The temperature induced shift of the fundamental and harmonic operating frequencies of the four configurations was measured at different temperatures in the range from −25 to 70 °C. The first order temperature coefficient of delay (TCD) of the four structures was experimentally evaluated for different film...

Surface Acoustic Waves in Reverse-Biased AlGaN/GaN Heterostructures

Abstract: Properties of surface acoustic waves (SAWs) in reverse-biased AlGaN/GaN heterostructures on (0001) sapphire substrates were studied by examining the characteristics of SAW filters composed of interdigital Schottky and ohmic contacts. The fundamental and higher frequency SAW signals in measured -parameters were attributed to Rayleigh and Sezawa modes, respectively. The onsets of the SAW signals, which were close to the threshold voltage of HEMTs in the vicinities of the respective filters, changed in response to the spatial variation of the threshold voltage. The onset of Sezawa mode was deeper than that of Rayleigh mode, and the difference in onset was larger for longer SAW wavelengths. These results are possibly explained by the change of the input capacitance of interdigital transducers due to the reverse-bias voltages or by the difference in the distribution of SAW energy between the two modes.

Electrostatic Microactuator Design Using Surface Acoustic Wave Devices

Abstract: An integration of low power operated Surface Acoustic Wave (SAW) devices with the electrostatic microactuators for microfluidic and similar applications is presented in this chapter. Passive, low power, and small area devices can be interrogated wirelessly using SAW devices, which can respond to a uniquely coded signal for a secure and reliable operation. The novel approach relies on converting the interrogating coded signal to surface acoustic wave that is then correlated with an embedded code. A theoretical analysis of how the actuation mechanism operates is carried out and simulation results of the new microactuator are discussed. At the initial analytical stage, for simplicity, a basic SAW delay line structure is used to generate an electrostatic field between output interdigital transducer (IDT) of the SAW device and a thin conductive plate (actuator), which is placed on top of the output IDT. The static and transient displacement analysis of the actuator is carried out using ANSYS simulation tools. A comparison between the static displacements obtained from ANSYS based simulations and Rayleigh-Ritz based analysis is also presented and discussed.

Piezoelectric substrate and surface acoustic wave filter using the same

Abstract: Disclosed are a piezoelectric substrate and a surface acoustic wave (SAW) filter. A piezoelectric substrate 10 a includes a base member 11 including an oxide layer 12 with a plurality of grooves 12 a on one surface of the base member 11 ; a buffer member 13 being formed on the oxide layer 12 to expose one end and another end of the oxide layer 12 ; an insulating member 14 being formed on another surface of the base member 11 ; and a piezoelectric member 15 being formed on the buffer member 13 . A SAW filter using the piezoelectric substrate 10 a , includes the base member 11 including the oxide layer 12 with the plurality of grooves 12 a on one surface; the buffer member 13 ; the insulating member 14 ; the piezoelectric member 15 ; and a plurality of interdigital transducer (IDT) electrodes 17 and 17 being formed on the piezoelectric member 15 to receive an electrical signal, filter the electrical signal, and output the filtered electrical signal.