ShearHorizontal Surface Acoustic WaveSensors BasedonPolyaniline forAmmoniaGasSensing (original) (raw)
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Guided SH-SAW sensors for liquid-phase detection
… Symposium and PDA …, 2001
The design and performance of guided shear horizontal surface acoustic wave (guided SH-SAW) devices on LiTaO 3 substrates are investigated for high sensitivity biochemical sensor in liquids. The device sensitivity to mass and viscoelastic loading is ...
SH-SAW sensor on langasite for mass detection in liquid media
CAS 2013 (International Semiconductor Conference), 2013
ABSTRACT This paper presents experimental realization of shear horizontal surface acoustic wave (SH-SAW) sensor on Langasite (LGS) for mass detection in liquid media. The presence of mycotoxins in food or pesticides in water supplies can produce grave implications on human health. Sensitive and selective sensors capable of quickly detecting the level of contamination with fungal toxins growing on grains in storage, are needed. Shear horizontal surface acoustic wave (SH-SAW) devices provide an attractive platform for the design of biosensors that operate in liquid media. The paper reports on a SH-SAW delay line designed and fabricated on langasite (LGS), Euler angles (0°, 22°, 90°). The SH-SAW devices have been fabricated using the microfabrication method by lift-off lithography process to define the patterns for the IDT structures. Frequency response of device was monitored using Anritsu vector network analyzer (VNA). A test setup was implemented for the characterization of LGS SH-SAW-based sensors.
Biosensors and Bioelectronics, 2004
In this work, we describe a novel pulse mode shear horizontal-surface acoustic wave (SH-SAW) polymer coated biosensor that monitors rapid changes in both amplitude and phase. The SH-SAW sensors were fabricated on 36 • rotated Y-cut X propagating lithium tantalate (36 YX.LT). The sensitivity of the device to both mass loading and visco-elastic effects may be increased by using a thin guiding layer of cross-linked polymer. Two acoustic modes are excited by the electrodes in this crystalline direction. Metallisation of the propagation path of the 36 YX.LT devices allows the two modes to be discriminated. Successive polymer coatings resulted in the observation of resonant conditions in both modes as the layer thickness was increased. Using the 36 YX.LT devices, we have investigated the application of a novel pulse mode system by sensing a sequence of deposition and removal of a biological layer consisting of vesicles of the phospholipid POPC. A continuous wave system was used to verify the accuracy of the pulse mode system by sensing a series of poly(ethylene glycol) (PEG) solutions. The data clearly demonstrates the ability of the 36 YX.LT pulse mode system to provide rapid measurements of both amplitude and phase for biosensing applications.
Guided Acoustic wave sensors for liquid environments
Journal of Physics D: Applied Physics
Surface acoustic wave (SAW) based sensors for applications to gaseous environments have been widely investigated since the last 1970s. More recently, the SAW-based sensors focus has shifted towards liquid-phase sensing applications: the SAW sensor contacts directly the solution to be tested and can be utilized for characterizing physical and chemical properties of liquids, as well as for biochemical sensor applications. The design of liquid phase sensors requires the selection of several parameters, such as the acoustic wave polarizations (i.e., elliptical, longitudinal and shear horizontal), the wave-guiding medium composition (i.e., homogeneous or non-homogeneous half-spaces, finite thickness plates or composite suspended membranes), the substrate material type and its crystallographic orientation. The paper provides an overview of different types of SAW sensors suitable for application to liquid environments, and intents to direct the attention of the designers to combinations of materials, waves nature and electrode structures that affect the sensor performances.
Surface Acoustic Wave (SAW) Sensors: Physics, Materials, and Applications
Sensors
Surface acoustic waves (SAWs) are the guided waves that propagate along the top surface of a material with wave vectors orthogonal to the normal direction to the surface. Based on these waves, SAW sensors are conceptualized by employing piezoelectric crystals where the guided elastodynamic waves are generated through an electromechanical coupling. Electromechanical coupling in both active and passive modes is achieved by integrating interdigitated electrode transducers (IDT) with the piezoelectric crystals. Innovative meta-designs of the periodic IDTs define the functionality and application of SAW sensors. This review article presents the physics of guided surface acoustic waves and the piezoelectric materials used for designing SAW sensors. Then, how the piezoelectric materials and cuts could alter the functionality of the sensors is explained. The article summarizes a few key configurations of the electrodes and respective guidelines for generating different guided wave patterns ...
Chemical liquid-phase detection using guided SH-SAW: theoretical simulation and experiments
… Control Symposium and …
Results are presented for direct chemical sensing in liquid environments using guided shear horizontal surface acoustic wave (SH-SAW) sensor platforms on 36° rotated Ycut LiTaO 3. Two different sensor geometries are theoretically analyzed. Complex bulk and shear moduli are utilized to represent the viscoelastic properties of the polymers and estimate their influence on the velocity shift and attenuation change, hence on the sensor characteristics. Experimental results are presented and discussed for dual delay line devices with a reference line coated with PMMA and a sensing line coated with a chemically sensitive polymer, which acts as both a guiding layer and a sensing layer. Various chemically sensitive polymers are investigated, and the tested analytes include toluene, ethylbenzene and xylene. Analytes in the low concentration (1 ppm to 60 ppm) range in aqueous solutions are tested. Stability, sensitivity and partial selectivity are investigated by varying the coating thickness and curing temperature for the chemically sensitive layer. Partition coefficients for polymer-aqueous analyte pairs are used to explain the observed trend in sensitivity. Both mass loading and the coating viscoelasticity change influence the sensor response. A low ppb level detection limit is estimated from the present experiment measurement.
Applications of Acoustic Wave Devices for Sensing in Liquid Environments
Applied Spectroscopy Reviews, 2006
Acoustic wave devices such as thickness shear mode (TSM) resonators and shear horizontal surface acoustic wave (SH-SAW) devices can be utilized for characterizing physical properties of liquids and for chemical sensor applications. Basic device configurations are reviewed and the relationships between experimental observables (frequency shifts and attenuation) and physical properties of liquids are presented. Examples of physical property (density and viscosity) determination and also of chemical sensing are presented for a variety of liquid phase applications. Applications of TSMs and polymer-coated guided SH-SAWs for chemical sensing and uncoated SH-SAWs for "electronic tongue" applications are also discussed.
Sensors (Basel, Switzerland), 2017
Surface acoustic wave (SAW) devices are well known for mass-sensitive sensor applications. In biosensing applications, chemical and biochemically evoked binding processes on surfaces are detected in liquid environments using delay line or resonator sensor configurations, preferably in combination with the appropriate microfluidic devices. All configurations share the common feature of analyzing the transmission characteristic of the propagating SAW. In this paper, a novel SAW-based impedance sensor type is introduced which uses only one interdigital transducer (IDT), simultaneously as the SAW generator and the sensor element. Here, the input port reflection coefficient S11 is measured at the IDT instead of the commonly used S21 transmission forward gain parameter. Thus, a sharp and distinct peak of the S11 spectrum is obtained, enabling a comfortable direct readout of the sensor signal. Proof of the concept was gained by analyzing the specific binding of the 4-mercaptophenylacetic a...
Analytical Chemistry, 2001
The design and performance of guided shear horizontal surface acoustic wave (guided SH-SAW) devices on LiTaO 3 substrates are investigated for high-sensitivity chemical and biochemical sensors in liquids. Despite their structural similarity to Rayleigh SAW, SH-SAWs often propagate slightly deeper within the substrate, hence preventing the implementation of high-sensitivity detectors. The device sensitivity to mass and viscoelastic loading is increased using a thin guiding layer on the device surface. Because of their relatively low shear wave velocity, various polymers including poly(methyl methacrylate) (PMMA) and cyanoethyl cellulose (cured or cross-linked) are investigated as the guiding layers to trap the acoustic energy near the sensing surface. The devices have been tested in biosensing and chemical sensing experiments. Suitable design principles for these applications are discussed with regard to wave guidance, electrical passivation of the interdigital transducers from the liquid environments, acoustic loss, and sensor signal distortion. In biosensing experiments, using near-optimal PMMA thickness of ∼2 µm, mass sensitivity greater than 1500 Hz/(ng/mm 2) is demonstrated, resulting in a minimum detection limit less than 20 pg/mm 2. For chemical sensor experiments, it is found that optimal waveguide thickness must be modified to account for the chemically sensitive layer which also acts to guide the SH-SAW. A detection limit of 780 (3 × peak-to-peak noise) or 180 ppb (3 × rms noise) is estimated from the present measurements for some organic compounds in water.