Shear Horizontal Surface Acoustic Wave Research Articles

Measurements of Particles in Liquid Using Shear-Horizontal Surface Acoustic Wave Sensor

not Available.

Pure SH-SAW propagation, transduction and measurements on KNbO/sub 3/

Potassium niobate (KNbO3) supports the electromechanically active pure shear horizontal surface acoustic wave (SH-SAW) mode along Z-axis cylinder orientations, Euler angles (phi, 90 degrees, 0 degrees), in which two uncoupled wave solutions exist: a purely mechanical sagittal Rayleigh SAW and a piezoelectrically stiffened pure SH-SAW. Within this family of cuts, a maximum electromechanical coupling coefficient for the pure SH-SAW, K2 = 53%, is observed along (0 degrees, 90 degrees, 0 degrees). This pure SH-SAW orientation also has the maximum value of electromechanical coupling observed along rotated Y-cut X propagation directions, Euler angles (0 degrees, theta, 0 degrees). The use of the pure SH-SAW mode is attractive for liquid-sensing applications because the SH-SAW is modestly attenuated by the adjacent liquid, unlike the generalized SAW (GSAW), which has particle displacement normal to the surface. This work investigates propagation and excitation properties of the SH-SAW and the shear horizontal bulk acoustic wave (SH-BAW) on single crystal KNbO3, Euler angles (0 degrees, 90 degrees, 0 degrees). Interdigital transducer (IDT) arrays are analyzed using boundary element method (BEM) techniques, addressing IDT properties such as: power partitioning between the SH-SAW and SH-BAW, SH-BAW radiation as a function of wave vector direction and radiation angle, and overall IDT impedance. The percentage of SH-SAW power to total input power is above 98% for IDTs containing 1.5 to 5.5 wavelengths of active electrodes with surrounding metalized regions. For nonmetalized regions outside the IDT, the ratio drops to between 1 and 2%, showing the importance of an energy trapping structure for efficient SH-SAW excitation and propagation along this orientation. Simulated and experimental IDT admittance results are compared, verifying the validity of the analysis performed. The reported measurements on the frequency variation with temperature indicate that the orientation considered is temperature compensated at about 8 degrees C. The surface of the SH-SAW devices fabricated have been loaded with deionized water and showed additional 1.6 dB transmission loss with respect to the unloaded surface, verifying the suitability of the pure SH-SAW mode on KNbO3 for liquid sensor applications.

Detection of Escherichia coli O157:H7 with langasite pure shear horizontal surface acoustic wave sensors

The toxigenic Escherichia coli O157:H7 bacterium has been connected with hemorrhagic colitis and hemolytic uremic syndrome, which may be characterized by diarrhea, kidney failure and death. On average, O157:H7 causes 73,000 illnesses, 2100 hospitalizations and 60 deaths annually in the United States alone. There is the need for sensors capable of rapidly detecting dangerous microbes in food and water supplies to limit the exposure of human and animal populations. Previous work by the authors used shear horizontal surface acoustic wave (SH SAW) devices fabricated on langasite (LGS) Euler angles (0 degrees, 22 degrees, 90 degrees) to successfully detect macromolecular protein assemblies. The devices also demonstrated favorable temperature stability, biocompatibility and low attenuation in liquid environments, suggesting their applicability to bacterial detection. In this paper, a biosensor test setup utilizing a small volume fluid injection system, stable temperature control and high frequency phase measurement was applied to validate LGS SH SAW biosensors for bacterial detection. The LGS SH SAW delay lines were fabricated and derivatized with a rabbit polyclonal IgG antibody, which selectively binds to E. coli O157:H7, in this case a non-toxigenic test strain. To quantify the effect of non-specific binding (negative control), an antibody directed against the trinitrophenyl hapten (TNP) was used as a binding layer. Test E. coli bacteria were cultured, fixed with formaldehyde, stained with cell-permeant nucleic acid stain, suspended in phosphate buffered saline and applied to the antibody-coated sensing surfaces. The biosensor transmission coefficient phase was monitored using a network analyzer. Phase responses of about 14 degrees were measured for the E. coli detection, as compared to 2 degrees due to non-specific anti-TNP binding. A 30:1 preference for E. coli binding to the anti-O157:H7 layer when compared to the anti-TNP layer was observed with fluorescence microscopy, thus confirming the selectivity of the antibody surface to E. coli.

ATR-FTIR spectroscopic analysis of sorption of aqueous analytes into polymer coatings used with guided SH-SAW sensors

Attenuated total internal reflectance Fourier transform infrared (ATR-FTIR) spectroscopy was used for the investigation of sorption of aqueous solutions of analytes into polymer coatings. A series of simple model polymers, such as poly(dimethylsiloxane), poly(epichlorhydrin), and poly(isobutylene), and films and analytes, such as aqueous solutions of ethylbenzene, xylenes, toluene, and nitrobenzene, were used to evaluate the use of ATR-FTIR spectroscopy as a screening tool for sensor development. The ratios of integrated infrared absorption bands provided a simple and efficient method for predicting trends in partition coefficients. Responses of polymer-coated guided shear horizontal surface acoustic wave (SH-SAW) sensor platforms to the series of analytes, using polymer coatings with similar viscoelastic properties, were consistent with ATR-FTIR predictions. Guided SH-SAW sensor responses were linear in all cases with respect to analyte concentration in the tested range. Comparison of ATR-FTIR data with guided SH-SAW sensor data identifies cases where mass loading is not the dominant contribution to the response of the acoustic wave sensor. ATR-FTIR spectra of nitrobenzene, coupled with computational chemistry, provided additional insight into analyte/polymer interactions.

Analysis of Liquid-Phase Chemical Detection Using Guided Shear Horizontal-Surface Acoustic Wave Sensors

Direct chemical sensing in liquid environments using polymer-guided shear horizontal surface acoustic wave sensor platforms on 36 degrees rotated Y-cut LiTaO3 is investigated. Design considerations for optimizing these devices for liquid-phase detection are systematically explored. Two different sensor geometries are experimentally and theoretically analyzed. Dual delay line devices are used with a reference line coated with poly (methyl methacrylate) (PMMA) and a sensing line coated with a chemically sensitive polymer, which acts as both a guiding layer and a sensing layer or with a PMMA waveguide and a chemically sensitive polymer. Results show the three-layer model provides higher sensitivity than the four-layer model. Contributions from mass loading and coating viscoelasticity changes to the sensor response are evaluated, taking into account the added mass, swelling, and plasticization. Chemically sensitive polymers are investigated in the detection of low concentrations (1-60 ppm) of toluene, ethylbenzene, and xylenes in water. A low-ppb level detection limit is estimated from the present experimental measurements. Sensor properties are investigated by varying the sensor geometries, coating thickness combinations, coating properties, and curing temperature for operation in liquid environments. Partition coefficients for polymer-aqueous analyte pairs are used to explain the observed trend in sensitivity for the polymers PMMA, poly(isobutylene), poly(epichlorohydrin), and poly(ethyl acrylate) used in this work.

Using Shear Horizontal Surface Acoustic Wave with Polyaniline Film as Ammonia Sensor

A shear horizontal surface acoustic wave (SH-SAW) sensor coated with polyaniline (PANI) was investigated in this study. The SH-SAW phase and attenuation were measured using a network analyzer. The sensor presented a sensitivity of 0.23 deg/ppm at 25°C. The minimum detection level was estimated to be 0.07 ppm at 25°C. Otherwise, the response of the SH-SAW sensor immediately followed the ammonia gas concentration. Hence, the SH-SAW coated with PANI exhibited an excellent response for detecting ammonia at room temperature.

Analysis of Shear Horizontal Surface Acoustic Wave Sensors with the Coupling of Modes Theory

This study has investigated a method for accurate analysis and design of shear horizontal surface acoustic wave (SH-SAW) sensors. The coupling of modes (COM) theory was used to develop an analytical model to satisfy Barkhausen's criteria for oscillation and avoid mode hopping. The theoretical simulation was highly consistent with the experimental results. The SH-SAW sensor presented here exhibited excellent reversibility, sensitivity, and repeatability when ammonia was at the ppb level.

Development of an SH-SAW sensor for the detection of DNA hybridization

We have developed SH (shear horizontal) surface acoustic wave (SAW) sensors for the detection of DNA (deoxyribonucleic acid) hybridization on the gold-coated delay line of transverse SAW devices. DNA hybridization experiments were performed with 15-mer oligonucleotides (probe and complementary target DNA). The sensor consists of twin SAW delay line oscillators (sensing channel and reference channel) operating at 100 MHz fabricated on 36° rotated Y-cut X-propagation LiTaO 3 piezoelectric single crystals. The relative change in the frequency of the two oscillators was monitored to detect hybridization between the target DNA and probe DNA immobilized on the delay line of the SAW sensor. The measurement results showed a good response of the sensor to the mass loading effects of the DNA hybridization with a sensitivity level up to 1.55 ng/ml/Hz.

SH-SAW Sensor for Superfluid 3He

We have developed a new technique to study the transverse acoustic properties of superfluid 3He, employing a shear horizontal surface acoustic wave (SH-SAW) sensor. The transverse acoustic impedance can be obtained from the velocity and damping of SH-SAW which acoustically couples with liquid 3He all the interface. Since ultrasonic measurements provide the information about superfluid order-parameter through the excitation of collective modes, the SH-SAW sensor is expected to be a useful tool to study the boundary effect of superfluid 3He. Preliminary measurements were carried out at pressures of 17 and 23 bar, by the pulse transmission method at a frequency of 70 MHz. At 17 bar, imaginary squashing mode was observed as the sharp drop of the imaginary part of acoustic impedance. At 23 bar, the supercooled A-B phase transition was observed, as a jump of the real part of acoustic impedance, which was not observed in the warming process.

Mass sensitivity of dual mode SAW delay lines on AlN∕sapphire structure

A surface acoustic wave (SAW) and a leaky shear horizontal SAW (SH-SAW) have been simultaneously excited along Al2O3[1 1 00] on an AlN(0001)/Al2O3(11 2 0) structure. Both modes are highly sensitive to surface mass loading. The measured mass sensitivities are in good agreement with theoretical prediction, and are comparable or higher than those reported on other SAW devices.

Functional Passive Sensor System Using Reflective SAW Delay Line

ABSTRACTA new passive and remote SAW sensor system having ID tag function is presented. Surface acoustic wave (SAW) devices have been widely used as a chemical and physical sensor for measuring the environment. SAW devices have been also used as identification tags (ID tags). The majority of the work reported on SAW sensors to date has used Rayleigh mode SAW and are concerning a delay line. The other hand, it has been shown that the sensors utilizing the shear horizontal mode SAW (SH-SAW) can be designed to sense the liquid properties. The SH-SAW has the unique characteristic of complete reflection at a 90 degree edge normal to the direction of the propagation. This characteristic makes it possible to construct a reflective delay line using the edge reflection. The reflective delay line can be used for as passive and remote sensing.In this paper, a passive and remote SAW sensor with a function of identification tags has been designed by using the reflective SH-SAW delay line. The reflective delay line was constructed on the 36 YX LiTaO3 substrate having a 90 degree edge normal to the direction of the SAW propagation. Passive and remote SAW sensor consists of several reflective delay lines having different propagation length. The passive sensor and ID tags were made by the multi-channel delay line. The responses of the sensor and ID tags using the edge reflection of SH-SAW are obtained in time domain. Several experiments were performed to verify the performances of the multi-channel edge reflection sensor. The basic characteristics of the reflective SAW sensor were obtained by measuring the amplitude and phase of reflected wave. The obtained results showed that the reflective SH-SAW sensor was very effective for sensing the physical and chemical properties.Wireless systems are also suggested for the effective operation of the passive SAW sensor. A novel and simple electronic circuit system for accurately measuring the phase characteristics of responses form multi-channel is proposed. In the application, the reflective delay line has been mounted on cantilever to monitor the strain experimentally. The variation of the SH-SAW velocity on the delay line caused by a strain was measured as the passive SAW sensor response. The velocity varied in proportion to the strain applied to the propagation surface. The results showed that the passive sensor was very effective to measure the strain in a wireless mode and it was found that the system is very suitable to health and safety monitoring of building or airplane wing.Finally it will be shown some applications of the wireless sensor with ID tags on the measurement of the conductivity and viscosity of same liquids.

A novel SH-SAW sensor system

This work has investigated some methods to solve the problems of non-steady operation and temperature interference which were easy to find in the shear horizontal surface acoustic wave (SH-SAW) sensing applications such as the gas sensor, liquid sensor and immunosensor. A programmable PLL circuit and independent LO input were applied to the multi-mixer to make it stable and accurate. A novel calibration and a precise temperature control were further used to reduce the temperature interference ten times. This system had good long-term stability and detected to ethanol successfully. Eventually, this system also clearly identified saline solution, orange juice, and ion supply drink.

Pure shear horizontal SAW biosensor on langasite

The undetected introduction of pathogens into food or water supplies can produce grave consequences in terms of economic loss and human suffering. Sensitive and selective sensors capable of quickly detecting microbial pathogens are urgently needed to limit the effects of bioterrorist incidents, accidents, or pollution. Shear horizontal surface acoustic wave (SH SAW) devices provide an attractive platform for the design of microbial biosensors that function in liquid media, where Rayleigh-type modes are rapidly attenuated. This paper reports on an exploratory SH SAW delay line designed and fabricated on langasite, La3Ga5SiO14 (LGS), along the novel Euler propagation direction (0 degrees, 22 degrees, 90 degrees). A liquid chamber was fabricated and attached to the top surface, and the device was submitted to liquid and biochemical tests. Moderate (6 dB) additional attenuation of the transmission coefficient, /S21/, was consistently observed when the SH SAW delay line was assembled in the test fixture and submitted to the liquid tests, indicating that LGS is an attractive candidate for liquid sensing. Sensor selectivity can be achieved by integrating the LGS SH SAW delay line with a biochemical recognition layer. A test setup was implemented for the characterization of LGS SH SAW-based biosensors. The delay line response to biomolecule binding was shown by detection of sequential binding of proteins to the SH SAW device delay path. The biotinylated sensor was exposed sequentially to biotin-binding deglycosylated avidin, biotin-modified rabbit IgG, and goat anti-rabbit IgG antibody. As each protein was bound to the sensing surface, marked changes in the delay-line phase were recorded. The reported results demonstrate the capability of these devices to act as biochemical detectors in aqueous solutions, and this work represents the first effort using the novel material LGS in SAW-based biosensor technology.

Development of Smart Tongue Devices for Measurement of Liquid Properties

In this paper, we describe the design and characterization of shear horizontal surface acoustic wave devices for the analysis of liquid samples. Devices were fabricated on both 36/spl deg/ rotated Y-cut X-propagating LiTaO/sub 3/ and LiNbO/sub 3/ substrates. The design consists of a dual delay-line configuration where one delay line is metallized and shielded, while the other is left electrically active. Experiments to characterize the devices in terms of sensitivity, temperature dependence, and mass loading have been conducted and the results presented. Different liquid samples, i.e., water, orange juice, and milk, are 100% linearly separable using principal components analysis. In addition, it is possible to measure the fat content (/spl plusmn/0.1%) as well as the freshness of full (whole) milk.

Propagation of a shear-horizontal surface acoustic mode in a periodically grooved AlN/Al2O3 microstructure

We investigate the shear-horizontal surface acoustic waves (SH-SAWs) generated on an AlN/Al2O3 microstructure by laser-micromachined grooves on the AlN film. In the absence of grooves, the AlN/Al2O3 device shows resonance for only a lower velocity SAW mode. However, when grooves of periodicity smaller than half the wavelength of the surface acoustic wave are micromachined, a higher velocity resonance due to a SH-SAW mode is observed in the device. It is found that our SH-SAW mode remains undamped and is able to propagate across the device when loaded with a biofluidic mass. We have also measured the mass sensitivity of the SH-SAW mode under biofludic load in terms of frequency shift. Measurements show that this mode has a very high mass sensitivity of the order 1.35 ng/ml, which suggests that the device can be applied for the detection of a small concentration of antigens in a biofluid. In this article, the fabrication and grooving techniques of the device are also addressed.

Miniature taste sensing system based on dual SH-SAW sensor device: an electronic tongue

We report on the design and performance of a novel analytical sensing system, a so-called electronic tongue; it is based upon a dual shear horizontal surface acoustic wave (SH-SAW) device that discriminates between liquids of different basic tastes. Sixty megahertz SH-SAW dual delay-line sensors were micro-fabricated on 36° rotated Y-cut X-propagating LiTaO3 and placed below a miniature PTFE housing containing the liquid under test. In this SAW sensor one delay-line is electrically shorted and the other is free. Synthetic samples were analyzed with the four basic tastes of sour, salt, bitter, and sweet. The electronic tongue classified correctly all of the different basic tastes without a selective biological or chemical coating. Theory relating to the electro-acoustic properties represented by the relative permittivity and conductivity of the sample liquid is presented and related to experimental results. Dilution tests have also been performed in order to determine the detection limit of this physical taste sensor and hence its application potential.

Characterization of epoxy resin (SU‐8) film using thickness‐shear mode (TSM) resonator under various conditions

AbstractCharacterization of an epoxy resin film, commonly known as SU‐8, is presented using thickness shear mode (TSM) quartz resonator. The impedance‐admittance characteristics of the equivalent circuit models of the unperturbed and coated resonators are analyzed to extract the storage modulus and loss modulus (G′ and G″). Those parameters are needed to establish SU‐8 film as an effective wave‐guiding layer in the implementation of guided shear‐horizontal surface acoustic wave (SH‐SAW) sensor platforms. Both cured and uncured polymer films are studied at the fundamental and third harmonic frequencies of the TSM resonators. The storage modulus (G′) and loss modulus (G″) of the SU‐8 film approach constant values of 1.66 × 1010 dyne/cm2 and 6.0 × 108 dyne/cm2, respectively, for relatively thicker films (>20 μm) at a relatively low frequency of 9 MHz. The most accurate values for the extracted shear moduli G (G = G′+ jG″) are obtained at high thickness where the viscoelastic contribution to the TSM response is substantial. The effect of temperature on the storage and loss moduli is determined for the range of −75 to 40 °C. It is found that the polymer approaches a totally glassy state below −60 °C. Exposure to water appears to follow Fickian diffusion behavior at short times and this exposure also results in changes to both G′ and G″. However, stability is rapidly reached with exposure to water, indicating relatively lower water absorption, consistent with the extracted diffusion coefficient. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2373–2384, 2004

Experimental Study of Love Wave Sensor Response by Phase and Group Velocity Measurement

The effect of dispersion on acoustic wave sensors is considered experimentally. A recent theoretical prediction that the phase velocity mass sensitivity of guided shear horizontal surface acoustic wave devices can be obtained using measurements of phase and group velocity, and that the group velocity is highly sensitive to mass loading, is investigated. Experimental data for a polymer-coated surface-skimming bulk wave device on an ST quartz substrate is presented. Measurements of phase velocity, group velocity, and insertion loss determined by a network analyzer were obtained by systematically increasing the guiding layer thickness. Liquid sensing using poly (ethylene glycol) solutions with increasing densities were performed and phase and group velocities measured. The increase in mass sensitivity with the guiding layer thickness is significant and the data confirms the theoretical prediction that group velocity is a more sensitive parameter than the phase velocity to liquid loading.

Application of Surface Acoustic Wave Sensors for Liquid Helium-4 and Helium-3

A surface acoustic wave (SAW) sensor can be used to determine the acoustic properties of liquid He. We applied this sensor for liquid 3He and liquid 4He. Two kinds of SAW were used in this experiment, Rayleigh-SAW and shear horizontal SAW. The damping of Rayleigh-SAW was measured in liquid 4He. The results agreed well with the reported values of the acoustic impedance, and the superfluid transition was clearly seen. The damping and the phase shift of shear horizontal SAW were measured in the normal liquid 3He. Temperature dependence of the damping and the phase shift was analyzed by the viscoelastic model, and the results were compared with the transverse acoustic impedance in the normal 3He.

Development of SH-SAW sensors for underwater measurement

We developed SH (shear horizontal) surface acoustic wave (SAW) sensors to detect protein molecules in liquid solutions applying a particular antibody thin film on the delay line of transverse SAW devices. The antibody investigated was human-immuno-globulin G (HigG) to hold the antigens (anti-HigG) in the protein solution to be measured. The sensor showed stable response to the mass loading effects of the anti-HigG molecules with the sensitivity up to 10.8 ng/ml/Hz.