Showing papers on "Interdigital transducer published in 2015"

Acoustothermal heating of polydimethylsiloxane microfluidic system

Abstract: We report an observation of rapid (exceeding 2,000 K/s) heating of polydimethylsiloxane (PDMS), one of the most popular microchannel materials, under cyclic loadings at high (~MHz) frequencies. A microheater was developed based on the finding. The heating mechanism utilized vibration damping in PDMS induced by sound waves that were generated and precisely controlled using a conventional surface acoustic wave (SAW) microfluidic system. The refraction of SAW into the PDMS microchip, called the leaky SAW, takes a form of bulk wave and rapidly heats the microchannels in a volumetric manner. The penetration depths were measured to range from 210 μm to 1290 μm, enough to cover most sizes of microchannels. The energy conversion efficiency was SAW frequency-dependent and measured to be the highest at around 30 MHz. Independent actuation of each interdigital transducer (IDT) enabled independent manipulation of SAWs, permitting spatiotemporal control of temperature on the microchip. All the advantages of this microheater facilitated a two-step continuous flow polymerase chain reaction (CFPCR) to achieve the billion-fold amplification of a 134 bp DNA amplicon in less than 3 min.

Transverse Mode Spurious Resonance Suppression in Lamb Wave MEMS Resonators: Theory, Modeling, and Experiment

Abstract: This paper presents a transverse mode suppression theory and its experimental verification through aluminum nitride Lamb wave resonators (LWRs) operating at 142 MHz An effective 2-D approximation model of the LWR is proposed, based on which the origin of transverse modes in LWR is investigated The displacement distribution, resonant frequencies, and electromechanical coupling coefficients $( k_{t}^{2})$ of the main mode and its auxiliary transverse modes are obtained A spurious mode suppression theory in terms of the expression of $k_{t}^{2}$ in the 2-D model is proposed Three kinds of electrodes are designed to suppress the transverse mode adjacent to the main mode, including a novel interdigital transducer gap technique that is reported for the first time With the applicable geometries, these methods reduce the spurious response from 118 to <05 dB, without significantly affecting the figure of merit of the resonator

Simulation of solidly mounted plate wave resonator with wide bandwidth using 0-th shear horizontal mode in LiNbO3 plate

Abstract: A cognitive radio system using a vacant frequency band of digital TV channels (TV white space) requires a tunable filter with wide tunable ranges of center frequency and bandwidth. An ultra-wideband resonator is a key device to implement the tunable filter, because the tunable range is limited by the bandwidth (BW) of the resonators. A 0-th shear horizontal (SH0) mode plate wave resonator using an ultra-thin LiNbO3 plate is known to have a large electromechanical coupling factor, i.e., a large BW, but the structural fragility of the ultra-thin LiNbO3 plate is problematic. In this study, the feasibility of solidly mounted resonator type SH0 mode plate wave resonator was investigated systematically by finite element method simulation. The design parameters including the Euler angle, thickness of a LiNbO3 plate, and the material and thickness of an interdigital transducer were optimized. With the best design, a BW as wide as 26% is obtained.

Study on generation mechanisms of second-order nonlinear signals in surface acoustic wave devices and their suppression

Abstract: In this study, we examine the generation mechanisms of the second-order nonlinear signals in surface acoustic wave resonators/duplexers fabricated on a 42°YX-LiTaO3 substrate. It is shown that the crystal asymmetry of the substrate can generate the second-order nonlinear signals. The following two mechanisms mainly contribute to their generation: (a) self-mixing of the electrostatic field and (b) mixing of the electrostatic field with the strain field associated with laterally propagating modes. Both of them occur at the gaps between the electrode tip and the dummy electrode. In addition, an interdigital transducer design that cancels this asymmetry is proposed. The design is applied to a one-port resonator and a duplexer, and the effectiveness of this technique is demonstrated.

Spatial mapping of focused surface acoustic waves in the investigation of high frequency strain induced changes

Abstract: The field of straintronics, in which strain is used to drive phase transitions, ordering and structural changes, has conventionally been limited to dc or low frequency strain. High frequency large strains, which have the potential to serve as a high frequency trigger of strain sensitive physical phenomena, can be generated using focused surface acoustic waves, which produce two dimensional standing strain waves with very high strain at the elliptical focus. Here, the strain standing wave pattern generated by a focused surface acoustic wave is mapped and quantified as a function of voltage and frequency with high spatial resolution. A knife-edge optical reflection method is used to map the strain standing wave pattern generated by a 87.95 MHz annular interdigital transducer on 128° Y-Cut LiNbO3. Subsequent to strain mapping, ferromagnetic Co/Pt multilayers nanostructures are lithographically patterned within the high strain region for preliminary measurements of magnetization changes arising from high frequency fast strain. The knife edge technique is simple, results in excellent spatial resolution and is fully compatible with other optical measurements, such as focused magneto-optic Kerr measurements, while maintaining spatial information. This ability to accurately and reproducibly determine the position of maximum strain and to lock onto a specific strain region is an important step in the investigation of the effects of high frequency strain on thin film materials, which range from magnetic reorientations to strain induced phase transitions.

SAW temperature sensor on Quartz

Abstract: For biomedical applications, narrow temperature range and high sensor accuracy requirements define the need for high temperature sensitivity. Wireless SAW sensors connected to antennas need a reference element to account for changes in electromagnetic coupling between the transmitter and receiver antennas. A pair of sensors with different temperature sensitivities may serve as a self-referenced sensor assembly. This justifies the need for materials with useful SAW resonator properties and with the largest difference between temperature coefficients of frequency (TCF) for a resonator pair on a single substrate. We have identified several cuts of quartz having useful properties with a TCF difference up to 140 ppm/°C for a pair of resonators on a single substrate. As a rule, placing such resonators on a single substrate requires their rotation by up to 90° relative to each other. The limited range of cuts presents a unique opportunity to place both resonators along the X+90° direction with one resonator using Bleustein-Gulyaev-Shimizu (BGS) waves (with electrodes placed along the x-axis) and the other one (with electrodes inclined by about ±10° to the x-axis) using quasi-Rayleigh waves. These cuts are close to the 70°Y cut where a high TCF difference is reached together with acceptable characteristics of the resonators. Resonators were designed for all useful cuts (including the 70°Y cut) and tested. The use of different periods in reflectors and interdigital transducer (IDT) together with individual choice of gaps between reflectors and IDT meant achieving low spurious content in resonator responses. The quality factors reached values up to 3500 at central frequencies around 915 MHz for both BGS and quasi-Rayleigh types of waves. The measured difference of the TCF is about 138 ppm//spl degC on 70°Y cut that is close to the calculated value.

Stator optimization and evaluation method in a surface acoustic wave motor

Abstract: The interdigital transducer (IDT) of a surface acoustic wave (SAW) motor comprises two unidirectional IDTs (U-IDTs), including a driving IDT (D-IDT) and a reflector IDT (R-IDT). In order to improve the conductance of the U-IDT, the distance between the D-IDT and the R-IDT will be adjusted. The novel U-IDT will be investigated by simulation and some measurements. The novel stator will be fabricated by the basic semiconductor planar process. On the other hand, a stator evaluation method for the SAW motor will be reported. Lastly, through the calculation of the wave power, the measured vibration amplitude and stator recycle efficiency will be unified.

Optimal orientations of LiTaO3 for application in plate mode resonators

Abstract: Optimal cuts of LiTaO3 for application in plate mode resonators were found via rigorous numerical investigations of zero- and higher-order plate modes propagating parallel or normal to the X-axis in rotated Y-cuts of LiTaO3; the plates were tested with a periodic metal grating on top of the plate and metal electrode present or absent on the plate bottom. In some cuts, high electromechanical coupling coefficients up to 20% could be combined with low or even zero temperature coefficients of frequency (TCF). Other cuts ensured moderate coupling of 12%–14% and low TCF in addition to high velocity of a higher-order plate mode up to 20 000 m/s. Metallization of a plate bottom helped to enhance coupling of certain modes. Interaction of a plate mode with electrodes of an interdigital transducer or with periodic metal gratings used for its excitation and reflection in resonators is illustrated by examples of dispersion plots. The nature of the analyzed modes was studied via visualization of the mechanical displacements accompanying wave propagation.

Microfluidic Injector Simulation With FSAW Sensor for 3-D Integration

Abstract: This paper presents a possible creation of the optimized liquid sensors for the inkjet nozzles. The proposed focused surface acoustic wave (FSAW) device utilizing aluminum nitride (AlN) single crystal as the piezoelectric substrate is based on the pressure variation due to the continuous droplet ejector. The design, specification, and numerical simulation results are described. Comparisons between the output response of the conventional and concentric structures indicate a more efficient operation of the multiple-segment focused interdigital transducer (FIDT) structure. According to the angular spectrum of the plane wave theory, the amplitude field of FIDTs is calculated through that of straight interdigital transducers. The 3-D integrated model of the FSAW device has a number of advantages, such as the enhancement of the surface displacement amplitudes and an easier fabrication. It is able to detect the breakup appearance of the liquid in the droplet formation process. For the piezoelectric substrate AlN, it is compatible with the CMOS fabrication technology, leading to an inexpensive and reliable system. Moreover, for the proposed FIDTs with multiple straight segments, the acoustic energy is more optimized and focused near the center of the inkjet nozzle. The droplet generation process begins at an output voltage of roughly 0.074 V within 0.25 $\mu \text{s}$ , and the background level of the attenuation of both the mechanical and electrical energy.

Highly sensitive strain sensors using surface acoustic wave on aluminum nitride thin film for wireless sensor networks

Abstract: We newly developed surface acoustic wave (SAW)-based strain sensors using aluminum nitride (AlN) films to integrate with oscillator circuits. An interdigital transducer (IDT) was fabricated on a layered structure consisting of AlN, Pt/Ti, and SiO2 deposited on a Si substrate. A SAW was excited in the piezoelectric AlN film and resonated at 107.8 MHz. The Q-factor and effective electromechanical coupling coefficient k eff 2 were 700 and 0.46% at the resonance, respectively. When we applied stress to the sensor, the resonant frequency was linearly changed with a sensitivity of 107.2 MHz/strain below the applied strain of the order of 10−5. The sensor can be fully fabricated at low temperature (<400 °C) and can be embedded in a one-chip oscillator by post-IC-process.

Micromachined ultrasound transducer using multiple piezoelectric materials

Abstract: A transducer includes first and second piezoelectric layers made of corresponding different first and second piezoelectric materials and three or more electrodes, implemented in two or more conductive electrode layers. The first piezoelectric layer is sandwiched between a first pair of electrodes and the second piezoelectric layer is sandwiched between a second pair of electrodes. The first and second pairs of electrodes contain no more than one electrode that is common to both pairs.

Acoustic surface wave based microfluidic plasma separating chip and method

Abstract: The invention discloses an acoustic surface wave based microfluidic plasma separating chip and method. The chip comprises a piezoelectric substrate, a set of interdigital transducer arranged on the piezoelectric substrate and a flow microchannel system which is arranged on the piezoelectric substrate in a bonding manner, located on one side of the interdigital transducer and has a necking structure. According to the chip, by use of width change of a microchannel, blood cells gradually shift to one side of a runner under the action of an acoustic radiation force, thus realizing the separation of plasma and blood cells. The chip takes such good advantages of the acoustic surface wave based microfluidic particle separation technology as high energy density and easy integration and manufacturing; in addition, only one set of interdigital transducer is arranged on the piezoelectric substrate and the distribution of an acoustic surface standing wave field is defined by a special geometrical shape of the PDMS flow microchannel; therefore, the defect that the existing acoustic surface wave based microfluidic particle separation technology requires two sets of interdigital transducer at the same time is overcome, the size of the separation chip is reduced further, and the requirement on alignment precision of the interdigital transducer and the microchannel system is reduced greatly.

Characterization of surface acoustic waves by stroboscopic white-light interferometry

Abstract: We present phase-sensitive absolute amplitude measurements of surface acoustic wave fields obtained using a stroboscopic white-light interferometer. The data analysis makes use of the high resolution available in the measured interferometric phase data, enabling the characterization of the out-of-plane surface vibration fields in electrically excited microstructures with better than 100 pm amplitude resolution. The setup uses a supercontinuum light source with tailored spectral properties for obtaining the high amplitude resolution. The duration of the light pulses is less than 300 ps to allow the detection of high frequencies. These capabilities enabled a detailed measurement of the focusing of surface acoustic waves by an annular interdigital transducer structure operating at 74 MHz, featuring a maximum vibration amplitude of 3 nm.

Super high frequency lithium niobate surface acoustic wave transducers up to 14 GHz

Abstract: We report lithium niobate (LiNbO3) surface acoustic wave (SAW) transducers with the smallest linewidth and the highest resonant frequency. A record 30 nm wide, 200 nm period (λ0) nanofabricated metallic structure on non-conductive LiNbO3 enables a frequency exceeding 14 GHz. At higher frequencies, greater data throughputs and improved sensor sensitivity are enabled. A systematic study of SAW devices from λ0=200−800 nm is presented taking into account crystal orientation, device design, patterning strategies, and resonant modes. The device performance metrics such as frequency, g-factor, insertion loss, and coupling coefficient are measured in detail and these metrics are also found to exceed the results of other recent state-of-the-art devices, when compared.

Surface acoustic wave (saw) resonator structure with dielectric material below electrode fingers

Abstract: A surface acoustic wave (SAW) resonator structure includes a substrate, a piezoelectric layer disposed on the substrate, and an interdigital transducer (IDT) electrode disposed over the piezoelectric layer. The IDT electrode includes multiple busbars and multiple electrode fingers extending from each busbar, where the electrode fingers are configured to generate surface acoustic waves in the piezoelectric layer. The SAW resonator structure further includes dielectric material disposed between the piezoelectric layer and at least at portion of the IDT. The dielectric material may be positioned below tips of the electrode fingers, thereby mass-loading the electrode fingers.

Fabrication and characterization of highly sensitive ZnO/Si SAW device with Pd selective layer for F2 gas sensing

Abstract: In this paper, ZnO nano thin film is prepared on n-type Si substrate with orientation using RF sputtering technique and a surface acoustic wave (SAW) based fluorine (F2) gas sensor integrated on ZnO with Palladium (Pd) on top as sensing layer is fabricated and characterized. The input and output interdigital transducer is fabricated of aluminum (Al) using nanolithography technique. The morphological characterization of ZnO thin film is done using scanning electron microscopy and atomic force microscopy. The XRD confirms the formation of ZnO nanostructured thin film. The voltage handling capability of the fabricated device is evaluated with negative and positive bias voltage. The study confirms that the SAW sensor based on ZnO/Si substrate and Pd sensing layer has good characteristic response of F2 gas with different concentration of gas from 0.5 to 20 ppm. The sensor shows good reproducibility and its sensitivity is approximately 2.4 kHz ppm?1.

Heating Microdroplets on a Piezoelectric Substrate Using Intermittent Surface Acoustic Wave

Abstract: A new method of heating microdroplets on a substrate is presented. An interdigital transducer was fabricated on a 1280 yx-LiNbO3 substrate using microelectric technology. Intermittent surface acoustic wave was excited by applying an amplitude-modulated signal to the interdigital transducer. The microdroplet to be heated was placed on the propagation path of the intermittent surface acoustic wave, which led to discontinuous acoustic streaming. Purified water and mineral oil microdroplets were demonstrated. Results show that the incremental temperature of the microdroplet is increased with the power of carrier signal, decreased with the frequency of modulation signal and the volume of the microdroplet.

Device and method for realizing splitting of micro-droplets in micro-channel under assistance of surface acoustic waves

Abstract: The invention discloses a device and a method for realizing splitting of micro-droplets in a micro-channel under the assistance of surface acoustic waves. The device comprises a piezoelectric substrate and a signal generator, wherein the micro-channel as well as a splitting unweighted interdigital transducer and a non-splitting unweighted interdigital transducer which are connected with the signal generator respectively are arranged on a working surface of the piezoelectric substrate, the two interdigital transducers are symmetrically distributed on two transverse sides of the front of the micro-channel, a flow blocking strip with the width smaller than that of the micro-channel is arranged in the front end of the back of the micro-channel, a sub-channel for conveying unsplit digital micro-droplets is formed by space between the second transverse outer side surface of the flow blocking strip and the second transverse inner side surface of the front end of the back of the micro-channel, the sub-channel is close to one side of the splitting unweighted interdigital transducer, and a plurality of mini-channels for splitting the digital micro-droplets are formed in the flow blocking strip. The device and the method have the advantages that the digital micro-droplets can be split by the aid of lower electric signal power, and the piezoelectric substrate can be well prevented from being broken.

Piezoelectric ceramic dual-frequency earphone structure

Abstract: A piezoelectric ceramic dual-frequency earphone structure includes an earphone housing, a dynamic transducer, a piezoelectric ceramic transducer and a circuit board. The piezoelectric ceramic transducer is installed in the receiving region. The piezoelectric ceramic transducer is connected to the dynamic transducer via a support unit and a positioning unit. The circuit board is assembled in the receiving region and connected to acoustic signal cables. The acoustic signal cables are connected to a dynamic voice coil of the dynamic transducer and the piezoelectric ceramic transducer. When electric signals are applied to a ceramic membrane of the piezoelectric ceramic transducer, a metal sheet of the piezoelectric ceramic transducer is vibrated to generate high frequency sound, and the high frequency sound are then mixed with the sound from the dynamic transducer.

High-performance anti-collision surface acoustic wave delay line type wireless sensor system

Abstract: The invention provides a high-performance anti-collision surface acoustic wave delay line type wireless sensor system. A transponder sensing chip input transducer is a code interdigital transducer (input dependence transponder), the codes of the transponder sensing chip input transducer are compatible codes which belong to the same compatible code group, and a transponder which adopts the same compatible code encoding chip is called a similar transponder. The transponder sensing chip is provided with at least two same-frequency output dependence transducers arranged along a sound track, and the preferable codes of the transponder sensing chip are barker codes. The starting delay distances of the first output transducers and the input transducers of different similar transponder chips are mutually different; intervals among all output transducers are consistent; and a design causes all echo peaks to be distinguished by a reader after electromagnetic echoes simultaneously generated by the similar transponders are overlapped within a test range of a nominal sensing amount. The reader is provided with a compatible code generation component and barker code demodulation component. The anti-collision function of the system is equal to a value obtained by that the number of different types of transponders is multiplied by a time sequence capacity.

Numerical Modelling and Experimental Verification of Interdigital Transducers for Lamb Wave Generation

Abstract: Recently, intensive research activity in the application of guided waves (GWs) for structural health monitoring (SHM) has been observed. Interdigital Transducer (IDT) is one of the types of transducers used for generating GWs. The main advantages of such transducers include their ability in generating directional and mode-selective waves. The parameters of IDTs have to be adjusted for the excited wavelength. Some geometric parameters as well as the properties of materials used for manufacturing transducers may be defined using widely known analytical relationships [1]. However, in order to accurately determine the parameters of the IDT, numerous simulations and their experimental verification are required [2]. The paper presents a novel, time efficient approach to the virtual prototyping of complex shaped transducers. The proposed procedure consists of the following four steps: (1) designing a transducer based on analytical relations, (2) approximate numerical simulations of designed transducers with a custom-made, computationally efficient code for screening tests, (3) detailed numerical tests employing the multiphysics Finite Element Method (FEM) for the developed IDT design and (4) experimental tests.

Displacement sensor based on interdigital capacitor

Abstract: In this paper we investigate the possibility of displacement detection by approaching dielectric plate to electrodes of interdigital capacitor. Working principle of this sensor is based on penetration depth of the fringing electric fields above capacitors electrodes and its intersection with dielectric plate. Tests were done with interdigital capacitor and dielectric plates fabricated in Low Temperature Co-fired Ceramic (LTCC) technology. Experimentally obtained results are compared with a theoretical model. Good agreement between measured results and parameters estimated by analytical calculations are obtained.

Highly reconfigurable Aluminum Nitride MEMS resonator using 12 monolithically integrated phase change material switches

Abstract: This paper presents the first demonstration of a frequency reconfigurable and programmable Aluminum Nitride (AlN) piezoelectric MEMS resonator using phase change material (PCM) based switchable electrodes For the first time, 12 miniaturized (2 µm×2 µm) PCM switches are monolithically integrated with an AlN MEMS resonator and used to reconfigure the terminal connections of the individual metal fingers composing the device interdigital transducer (IDT) This innovative design solution provides high ON/OFF ratio switching of the acoustic resonance (∼28X impedance variation at resonance), and reconfiguration of the device electromechanical coupling (k t 2: 0–132%), capacitance (C: 125-1,134 fF), and operating frequency (f 1 ∼1813 MHz, f 2 ∼3854 MHz)

Love wave device structure and detecting method for liquid multiparameter sensing

Abstract: The invention discloses a love wave device structure and detecting method for liquid multiparameter sensing. The love wave device structure comprises a piezoelectric substrate, a piezoelectric film, a first reflecting grating, a second reflecting grating, an interdigital transducer, a first liquid sensitive area and a second liquid sensitive area. The interdigital transducer is deposited at the middle portion of the piezoelectric substrate surface, the first reflecting grating (3) and the second reflecting grating (4) are deposited at the left side and the right side of the piezoelectric substrate surface respectively, the piezoelectric film is sputtered on the piezoelectric substrate surface, the first liquid sensitive area is arranged between the first reflecting grating and the interdigital transducer, and the second liquid sensitive area is arranged between the second reflecting grating and the interdigital transducer. The love wave device structure and detecting method for liquid multiparameter sensing has the advantages that parallel detection on liquid density, viscosity, dielectric constant and specific conductance is realized only with one love wave device, influence of liquid volumetric modulus of elasticity to a measuring result can be eliminated, and a passive wireless function is possessed.

Acoustic surface wave temperature sensor

Abstract: The invention discloses an acoustic surface wave temperature sensor which comprises a piezoelectric ceramic substrate, a reflection grating and an interdigital transducer, wherein the interdigital transducer adopts a Chebyshev window function as an apodization weighing design of a weighting function. According to the acoustic surface wave temperature sensor adopting the apodization weighing of the Chebyshev window function, the suppression capacity of the temperature sensor for a sidelobe in a frequency response characteristic is improved, the problem of difficulty in main lobe identification in device frequency response is solved, the accuracy and the practicability of the acoustic surface wave temperature sensor are improved, and the temperature sensor is high in frequency temperature characteristic.

Filter device and duplexer

Abstract: In a filter device, first and second filter sections are connected in parallel between an input terminal and an output terminal. The first filter section is a longitudinally coupled resonator-type elastic wave filter including first and second inter-stage wiring lines with a two-stage cascading connection. The second filter section is a longitudinally coupled resonator-type elastic wave filter including third and fourth inter-stage wiring lines with a two-stage cascading connection. The phases of signals flowing in the third inter-stage wiring line and the second inter-stage wiring line are inverse. Terminal portions of an interdigital transducer electrode connected to the second inter-stage wiring line and an interdigital transducer electrode connected to the third inter-stage wiring line that are connected to a potential that is not a hot-side potential are connected by a virtual ground wiring line. A hot-side wiring portion that is adjacent to the virtual ground wiring line is disposed on an insulating film provided on the piezoelectric substrate.

Printed interdigital electrodes on plastic film for tumor cells density monitoring.

Abstract: Printed sensor has been introduced as a rapid and cost-effective platform for biomedical applications, especially for wearable biosensing and point-of-care diagnosis. In this paper, we reported a tumor cell density monitoring device with printed interdigital electrodes on a plastic film. Numerical simulation of electrical impedance spectroscopy shows good agreement with the experimental measurement of DI water and PBS solution. Different concentrations of cancer cells were used to demonstrate the capability of cell culture monitoring. The developed device is highly cost-effective and easy for fabrication, which may have great potentials in low-cost analysis of biological cells. In a word, this paper shows a more rapid and simple cell counting method as compared to tedious microscope cell counting.

Surface acoustic wave temperature and pressure sensor

Abstract: The utility model provides a surface acoustic wave temperature and pressure sensor. The sensor comprises a substrate, two delay-type surface acoustic wave sensor figures which are a pressure figure and a temperature figure, the pressure figure and the temperature figure comprise one-way interdigital transducers and a plurality of reflecting gratings, the one-way interdigital transducer of the pressure figure and the one-way interdigital transducer of the temperature figure are connected, a base is fixed under the substrate, a pressure conducting hole is formed in the base and below the reflecting gratings of the pressure figure, the base is also provided with a cover top, and a cavity is formed by the cover top and the base. According to the surface acoustic wave temperature and pressure sensor provided by the utility model, two close temperature measuring and pressure measuring sensors are arranged on the same substrate, the same temperature coefficient is utilized, temperature is accurately measured and automatic temperature compensation of pressure measuring values is realized, thereby achieving the aim of simultaneous accurate measurement of temperature and pressure.