Journal articles: 'Surface acoustic wave sensors (SAW)'

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Filipiak, Jerzy, Lech Solarz, and Grzegorz Steczko. "Surface Acoustic Wave (SAW) Vibration Sensors." Sensors 11, no. 12 (December 19, 2011): 11809–32. http://dx.doi.org/10.3390/s111211809.

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He, X. L., J. Zhou, W. B. Wang, W. P. Xuan, D. J. Li, S. R. Dong, H. Jin, Y. Xu, and J. K. Luo. "Flexible Surface Acoustic Wave Based Temperature and Humidity Sensors." MRS Proceedings 1659 (2014): 75–80. http://dx.doi.org/10.1557/opl.2014.111.

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ABSTRACTFlexible surface acoustic wave (SAW) based temperature and humidity sensors were fabricated and characterized. ZnO piezoelectric films were deposited on polyimide substrates by DC magnetron sputtering. ZnO films possess (0002) crystal orientation with large grain sizes of 50∼70 nm. SAW devices showed two wave modes, namely the Rayleigh and Lamb modes, with the frequencies at fR ∼132MHz and fL∼427MHz respectively for a wavelength of 12 μm device. The two resonant frequencies have a temperature coefficient of frequency (TCF) of −423ppm/K and −258ppm/K for the Rayleigh and Lamb waves, respectively. The SAW sensors exhibited a good repeatability in responding to cyclic change of humidity. The responses of the sensors increase with the increase in humidity, and the sensitivity increases with the decrease in wavelength. A high sensitivity of 34.7 kHz/10%RH has been obtained from a SAW device without any surface treatment, demonstrated that the flexible SAW humidity sensors are very promising for application in flexible sensors and microsystems.

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Xu, Zhangliang, and Yong J. Yuan. "Quantification ofStaphylococcus aureususing surface acoustic wave sensors." RSC Advances 9, no. 15 (2019): 8411–14. http://dx.doi.org/10.1039/c8ra09790a.

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Quartz crystal microbalance (QCM), surface acoustic wave (SAW)-Rayleigh and ZnO based SAW-Love sensors were fabricated and their sensitivity was comparatively analyzed for the quantification ofStaphylococcus aureus(S. aureus).

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Li, Yuanyuan, Wenke Lu, Changchun Zhu, Qinghong Liu, Haoxin Zhang, and Chenchao Tang. "Circuit Design of Surface Acoustic Wave Based Micro Force Sensor." Mathematical Problems in Engineering 2014 (2014): 1–9. http://dx.doi.org/10.1155/2014/701723.

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Pressure sensors are commonly used in industrial production and mechanical system. However, resistance strain, piezoresistive sensor, and ceramic capacitive pressure sensors possess limitations, especially in micro force measurement. A surface acoustic wave (SAW) based micro force sensor is designed in this paper, which is based on the theories of wavelet transform, SAW detection, and pierce oscillator circuits. Using lithium niobate as the basal material, a mathematical model is established to analyze the frequency, and a peripheral circuit is designed to measure the micro force. The SAW based micro force sensor is tested to show the reasonable design of detection circuit and the stability of frequency and amplitude.

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Palla-Papavlu, Alexandra, Stefan Ioan Voicu, and Maria Dinescu. "Sensitive Materials and Coating Technologies for Surface Acoustic Wave Sensors." Chemosensors 9, no. 5 (May 10, 2021): 105. http://dx.doi.org/10.3390/chemosensors9050105.

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Since their development, surface acoustic wave (SAW) devices have attracted much research attention due to their unique functional characteristics, which make them appropriate for the detection of chemical species. The scientific community has directed its efforts toward the development and integration of new materials as sensing elements in SAW sensor technology with a large area of applications, such as for example the detection of volatile organic compounds, warfare chemicals, or food spoilage, just to name a few. Thin films play an important role and are essential as recognition elements in sensor structures due to their wide range of capabilities. In addition, other requisites are the development and application of new thin film deposition techniques as well as the possibility to tune the size and properties of the materials. This review article surveys the latest progress in engineered complex materials, i.e., polymers or functionalized carbonaceous materials, for applications as recognizing elements in miniaturized SAW sensors. It starts with an overview of chemoselective polymers and the synthesis of functionalized carbon nanotubes and graphene, which is followed by surveys of various coating technologies and routes for SAW sensors. Different coating techniques for SAW sensors are highlighted, which provides new approaches and perspective to meet the challenges of sensitive and selective gas sensing.

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Länge, Kerstin. "Bulk and Surface Acoustic Wave Sensor Arrays for Multi-Analyte Detection: A Review." Sensors 19, no. 24 (December 6, 2019): 5382. http://dx.doi.org/10.3390/s19245382.

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Bulk acoustic wave (BAW) and surface acoustic wave (SAW) sensor devices have successfully been used in a wide variety of gas sensing, liquid sensing, and biosensing applications. Devices include BAW sensors using thickness shear modes and SAW sensors using Rayleigh waves or horizontally polarized shear waves (HPSWs). Analyte specificity and selectivity of the sensors are determined by the sensor coatings. If a group of analytes is to be detected or if only selective coatings (i.e., coatings responding to more than one analyte) are available, the use of multi-sensor arrays is advantageous, as the evaluation of the resulting signal patterns allows qualitative and quantitative characterization of the sample. Virtual sensor arrays utilize only one sensor but combine it with enhanced signal evaluation methods or preceding sample separation, which results in similar results as obtained with multi-sensor arrays. Both array types have shown to be promising with regard to system integration and low costs. This review discusses principles and design considerations for acoustic multi-sensor and virtual sensor arrays and outlines the use of these arrays in multi-analyte detection applications, focusing mainly on developments of the past decade.

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Giffney, Timothy J., Y. H. Ng, and K. C. Aw. "A Surface Acoustic Wave Ethanol Sensor with Zinc Oxide Nanorods." Smart Materials Research 2012 (December 26, 2012): 1–4. http://dx.doi.org/10.1155/2012/210748.

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Surface acoustic wave (SAW) sensors are a class of piezoelectric MEMS sensors which can achieve high sensitivity and excellent robustness. A surface acoustic wave ethanol sensor using ZnO nanorods has been developed and tested. Vertically oriented ZnO nanorods were produced on a ZnO/128∘ rotated Y-cut LiNbO3 layered SAW device using a solution growth method with zinc nitrate, hexamethylenetriamine, and polyethyleneimine. The nanorods have average diameter of 45 nm and height of 1 μm. The SAW device has a wavelength of 60 um and a center frequency of 66 MHz at room temperature. In testing at an operating temperature of 270 with an ethanol concentration of 2300 ppm, the sensor exhibited a 24 KHz frequency shift. This represents a significant improvement in comparison to an otherwise identical sensor using a ZnO thin film without nanorods, which had a frequency shift of 9 KHz.

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Jeng, Ming-Jer, Mukta Sharma, Ying-Chang Li, Yi-Chen Lu, Chia-Yu Yu, Chia-Lung Tsai, Shiang-Fu Huang, Liann-Be Chang, and Chao-Sung Lai. "Surface Acoustic Wave Sensor for C-Reactive Protein Detection." Sensors 20, no. 22 (November 19, 2020): 6640. http://dx.doi.org/10.3390/s20226640.

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A surface acoustic wave (SAW) sensor was investigated for its application in C-reactive protein (CRP) detection. Piezoelectric lithium niobate (LiNbO3) substrates were used to study their frequency response characteristics in a SAW sensor with a CRP sensing area. After the fabrication of the SAW sensor, the immobilization process was performed for CRP/anti-CRP interaction. The CRP/anti-CRP interaction can be detected as mass variations in the sensing area. These mass variations may produce changes in the amplitude of sensor response. It was clearly observed that a CRP concentration of 0.1 μg/mL can be detected in the proposed SAW sensor. A good fitting linear relationship between the detected insertion loss (amplitude) and the concentrations of CRP from 0.1 μg/mL to 1 mg/mL was obtained. The detected shifts in the amplitude of insertion loss in SAW sensors for different CRP concentrations may be useful in the diagnosis of risk of cardiovascular diseases.

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Liu, Boquan. "Super-resolution measurement method for passive wireless resonant surface acoustic wave sensor." Sensor Review 40, no. 1 (January 27, 2020): 107–11. http://dx.doi.org/10.1108/sr-07-2019-0173.

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Purpose This study aims to use resonant surface acoustic wave (SAW) sensors, which have advantages in the harsh application environments, to measure different physical parameters such as temperature, pressure and force. For SAW sensors, the locality in measurement resolution by the effective time is poor, it cannot give the detailed results of SAW echoes. Design/methodology/approach To promote the application of SAW sensor, this paper proposes a convex program-based super-resolution measurement method to recover the missing spectral line and enhance frequency resolution. Findings The proposed method reduces the reliance on effective time and improves the measurement resolution of SAW sensors. The performance was validated by experiments. Originality/value The limited resolution capability restricts the benefit of SAW technology in harsh environments. The proposed method shed light on SAW measurement resolution increase, exploiting its full potential and leading to commercial applications.

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Wang, Wei Na, and Qing Fan. "Tire Pressure Monitoring System and Wireless Passive Surface Acoustic Wave Sensor." Applied Mechanics and Materials 536-537 (April 2014): 333–37. http://dx.doi.org/10.4028/www.scientific.net/amm.536-537.333.

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The TPMS can not only save fuel and protect the tire, but also make the driver more safety. Tire safety is attracting the driver's attention, the United States had developed laws to enforce the TPMS installation in the car and the deadline is in 2008. In this paper, the basic structure and the implement method of TPMS are introduced. The active sensors are already used in most of the TPMS applications. The SAW theory and some wireless passive SAW pressure and temperature sensors which suit for the TPMS application are illustrated, because the passive sensor is becoming the focus in the TPMS research field. Passive SAW sensor is the good choice for TPMS, according to its wireless, passive, zero age rate, small size etc. The wireless passive SAW TPMS is one of the most important research direction. In this paper, some kinds of passive SAW sensor are introduced, which are used in TPMS.

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Mukhin, Nikolay V. "Microfluidic Acoustic Metamaterial SAW Based Sensor." Journal of the Russian Universities. Radioelectronics 22, no. 4 (October 1, 2019): 75–81. http://dx.doi.org/10.32603/1993-8985-2019-22-4-75-81.

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Introduction. Microacoustic sensors based on surface acoustic wave (SAW) devices allow the sensor integration into a wafer based microfluidic analytical platforms such as lab-on-a-chip. Currently exist various approaches of application of SAW devices for liquid properties analysis. But this sensors probe only a thin interfacial liquid layer. The motivation to develop the new SAW-based sensor is to overcome this limitation. The new sensor introduced here uses acoustic measurements, including surface acoustic waves (SAW) and acoustic methamaterial sensor approaches. The new sensor can become the starting point of a new class of microsensor. It measures volumetric properties of liquid analytes in a cavity, not interfacial properties to some artificial sensor surface as the majority of classical chemical and biochemical sensors.Objective. The purpose of the work is to find solutions to overcome SAW-based liquid sensors limitations and the developing of a new sensor that uses acoustic measurements and includes a SAW device and acoustic metamaterial.Materials and methods. A theoretical analysis of sensor structure was carried out on the basis of numerical simulation using COMSOL Multiphysics software. Lithium niobate (LiNbO3) 127.86° Y-cut with wave propagation in the X direction was chosen as a substrate material. Microfluidic structure was designed as a set of rectangular shape channels. A method for measuring volumetric properties of liquids, based on SAW based fluid sensor concept, comprising the steps of: (a) providing sensor structure with the key elements: a SAW resonator, a high-Q set of liquid-filled cavities and intermediate layer with artificial elastic properties between them; (b) measuring of resonance frequency shift, associated with the resonance in liquid-filled cavity, in the response of weakly coupled resonators of SAW resonator loaded by periodic microfluidic structure; (c) determination of volumetric properties of the fluid on the basis of a certain relationship between the speed of sound in liquid, the resonant frequency of the set of liquid-filled cavities, and the geometry design of the cavity.Results. The new sensor approach is introduced. The eigenmodes of the sensor structure with a liquid analyte are carried out. The characteristic of sensor structure is determined. The key elements of introduced microfluidic sensor are a SAW structure, an acoustic metamaterial with a periodic set of microfluidic channels. The SAW device acts as electromechanical transducer. It excites surface waves propagating in the X direction lengthwise the periodic structure and detects the acoustic load generated by the microfluidic structure resonator. The origin of the sensor signal is a small frequency change caused by small variations of acoustic properties of the analyte within the set of microfluidic channels.Conclusion. The principle of the new microacoustic sensor, which can become the basis for creating a new class of microfluidic sensors, is shown.

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Dbibih, Fatima-Ezzahraa, Meddy Vanotti, Valerie Soumann, Jean-Marc Cote, Lyes Djoumi, and Virginie Blondeau-Patissier. "Measurement of PM10 and PM2.5 Using SAW Sensors-Based Rayleigh Wave and Love Wave." Engineering Proceedings 6, no. 1 (May 17, 2021): 81. http://dx.doi.org/10.3390/i3s2021dresden-10129.

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Particulate matter (PM) is reported to be dangerous and can cause respiratory and health issues. Regulations, based on PM concentration, have been implemented to limit human exposition to air pollution. An innovative system with surface acoustic wave (SAW) sensors combined with a 3 Lpm cascade impactor was developed by our team for real time mass concentration measurements. In this study, we compare the PM sensitivity of two types of SAW sensors. The first one consists of delay lines based on Rayleigh waves propagating on a Lithium Niobate Y-X 128° substrate. The second one is a based-on Love waves on AT-Quartz. Aerosols were generated from NaCl for PM2.5 and from Silicon carbide for PM10. The sensors’ responses was compared to a reference sensor based on optical measurements. The sensitivity of the Rayleigh wave-based sensor is clearly lower than the Love wave sensor for both PMs. Although less sensitive, Rayleigh wave sensors remain very promising for the development of self-cleaning sensors using RF power due to their high electromechanical factor. To check the performance of our system in real conditions, we tested the sensitivity to PM from cigarette smoke using Rayleigh SAW. The PM2.5 stage showed a phase shift while the PM10 did not respond. This result agrees with previous studies which reported that the size of particles from cigarette smoke varies between 0.1 to 1.5 µm. A good correlation between the reference sensor’s response and the phase variation of SAW sensors was obtained.

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Ha, Nguyen Hai, Nguyen Hoang Nam, Dang Duc Dung, Nguyen Huy Phuong, Phan Duy Thach, and Hoang Si Hong. "Hydrogen Gas Sensing Using Palladium-Graphene Nanocomposite Material Based on Surface Acoustic Wave." Journal of Nanomaterials 2017 (2017): 1–6. http://dx.doi.org/10.1155/2017/9057250.

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We report the fabrication and characterization of surface acoustic wave (SAW) hydrogen sensors using palladium-graphene (Pd-Gr) nanocomposite as sensing material. The Pd-Gr nanocomposite as sensing layer was deposited onto SAW delay line sensor-based interdigitated electrodes (IDTs)/aluminum nitride (AlN)/silicon (Si) structure. The Pd-Gr nanocomposite was synthesized by a chemical route and deposited onto SAW sensors by air-brush spraying. The SAW H2 sensor using Pd-Gr nanocomposite as a sensing layer shows a frequency shift of 25 kHz in 0.5% H2 concentration at room temperature with good repeatability and stability. Moreover, the sensor showed good linearity and fast response/recovery within ten seconds with various H2 concentrations from 0.25 to 1%. The specific interaction between graphene and SAW transfer inside AlN/Si structures yields a high sensitivity and fast response/recovery of SAW H2 sensor based on Pd-Gr/AlN/Si structure.

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Hu, Baofa, Zhiwei Li, Yuanjie Wan, Peng Zhou, Chunquan Zhang, and Haisheng San. "3D Printed Pressure Sensor Based on Surface Acoustic Wave Resonator." Measurement Science Review 21, no. 3 (June 1, 2021): 76–81. http://dx.doi.org/10.2478/msr-2021-0011.

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Abstract This paper reports a 3-dimentional (3D) pressure sensor based on surface acoustic wave (SAW) resonators. The SAW resonators were designed and fabricated on 128°Y-X LiNbO3 substrate using the MEMS technology. The pressure sensing structure was 3D-printed using polyactic acid plastic, and two SAW resonators were integrated in the 3D-printed chamber structure for both temperature and pressure sensing. The SAW-based gas pressure sensors demonstrate a sensitivity of 589 ppm/MPa at the pressure range of 100-600 kPa and temperature of 40 °C.

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Koleshko, V. M., Yu V. Meshkov, and V. B. Strel'chik. "Surface acoustic wave (SAW) sensors from monocrystalline quartz." Measurement Techniques 31, no. 9 (September 1988): 857–59. http://dx.doi.org/10.1007/bf00863881.

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Xu, Sheng, Rui Zhang, Junpeng Cui, Tao Liu, Xiuli Sui, Meng Han, Fu Zheng, and Xiaoguang Hu. "Surface Acoustic Wave DMMP Gas Sensor with a Porous Graphene/PVDF Molecularly Imprinted Sensing Membrane." Micromachines 12, no. 5 (May 12, 2021): 552. http://dx.doi.org/10.3390/mi12050552.

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In this paper, surface acoustic wave (SAW) sensors containing porous graphene/PVDF (polyvinylidene fluoride) molecularly imprinted sensitive membrane for DMMP gas detection were investigated. A 433 MHz ST-cut quartz SAW resonator was used to convert gas concentration changes into frequency shifts by the sensors. The porous graphene/PVDF film was fabricated on the sensor’s surface by using the tape-casting method. DMMP molecules were adsorbed on the porous structure sensing film prepared by the 2-step method to achieve the specific recognition effect. The sensitivity of the sensor could reach −1.407 kHz·ppm−1. The response time and recovery time of the SAW sensor with porous graphene/PVDF sensing membrane were about 4.5 s and 5.8 s at the concentration of 10 ppm, respectively. The sensor has good anti-interference ability to most gases in the air.

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Chen, Jinkai, Wenbo Wang, Weipeng Xuan, Xiaozhi Wang, Shurong Dong, Sean Garner, Pat Cimo, and Jikui Luo. "Flexible surface acoustic wave broadband strain sensors based on ultra-thin flexible glass substrate." MRS Advances 1, no. 21 (2016): 1519–24. http://dx.doi.org/10.1557/adv.2016.110.

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ABSTRACTFlexible SAW devices based on ZnO piezoelectric thin film deposited on ultra-thin flexible glass were fabricated and their performances as a strain sensor have been investigated. The XRD and AFM characterizations showed that the ZnO layers have good crystal quality and smooth surface. The flexible SAW devices show excellent strain sensitivity which increases from ∼87 to ∼137 Hz/με with the increasing ZnO thickness, and the sensors can withstand strains up to ∼3000 με, 4∼6 times larger than those of SAW strain sensors on rigid substrates. The sensors exhibited remarkable stability up to hundreds of times bending under large strains. The effects of environmental variables (temperature, humidity, UV light) on the sensor performance have been investigated. The temperature has a significant effect on the performance of the SAW strain sensor, while humidity and light have limited effect.

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Ying, Zhi Hua, Jia Hu, Cong Ping Wu, Yi Qing Yang, Liang Zheng, and Kai Xin Song. "Bilayer Structure Based Surface Acoustic Wave Sensor for Formaldehyde Detection." Advanced Materials Research 664 (February 2013): 986–89. http://dx.doi.org/10.4028/www.scientific.net/amr.664.986.

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This study contributes to the measurements of formaldehyde at room temperature. A bilayer structure based surface acoustic wave (SAW) sensor has been fabricated and experimentally studied. The coating materials carbon nanotubes (CNTs) and poly (4-vinylphenol) (P4VP) were deposited by a spray-painting method onto SAW sensors configured as 433.92MHz two-port resonator-based oscillators. The results display high sensitivity and entirely reversibility. The response and recovery times of the bilayer structure are very short, and the response values are obviously greater than plus of the two single layers. Some sensing mechanisms between analytes and the bilayer structure SAW sensor will be discussed preliminarily.

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Pan, Yong, Ning Mu, Bo Liu, Bingqing Cao, Wen Wang, and Liu Yang. "A Novel Surface Acoustic Wave Sensor Array Based on Wireless Communication Network." Sensors 18, no. 9 (September 6, 2018): 2977. http://dx.doi.org/10.3390/s18092977.

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A novel surface acoustic wave (SAW) sensor array based on wireless communication network is prepared. The array is composed of four SAW sensors, a wireless communication network module, and a global positioning system (GPS) module. The four SAW sensors of the array are coated with triethanolamine, polyepichlorohydrin, fluoroalcoholpolysiloxane, and L-glutamic acid hydrochloride to detect hydrogen sulfide (H2S), 2-chloroethyl ethyl sulfide (CEES), dimethylmethylphosphonate (DMMP), and ammonia (NH3) at film thicknesses of 50–100 nm. The wireless communication network module consists of an acquisition unit, a wireless control unit, and a microcontroller unit. By means of Zigbee and Lora technologies, the module receives and transmits the collected data to a PC work station in real-time; moreover, the module can control the sensor array’s working mode and monitor the working status. Simultaneously, the testing location is determined by the GPS module integrated into the SAW sensor array. H2S, CEES, DMMP, and NH3 are detected in 300 m at different concentrations. Given the practical future application in environment in the future, the low, safe concentrations of 1.08, 0.59, 0.10, and 5.02 ppm for H2S, CEES, DMMP, and NH3, respectively, are detected at the lowest concentration, and the sensitivities of different sensors of the sensor array are 32.4, 14.9, 78.1 and 22.6 Hz/ppm, respectively. With the obtained fingerprints and pattern recognition technology, the detected gases can be recognized.

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Puiu, Mihaela, Lucian-Gabriel Zamfir, Valentin Buiculescu, Angela Baracu, Cristina Mitrea, and Camelia Bala. "Significance Testing and Multivariate Analysis of Datasets from Surface Plasmon Resonance and Surface Acoustic Wave Biosensors: Prediction and Assay Validation for Surface Binding of Large Analytes." Sensors 18, no. 10 (October 19, 2018): 3541. http://dx.doi.org/10.3390/s18103541.

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In this study, we performed uni- and multivariate data analysis on the extended binding curves of several affinity pairs: immobilized acetylcholinesterase (AChE)/bioconjugates of aflatoxin B1(AFB1) and immobilized anti-AFB1 monoclonal antibody/AFB1-protein carriers. The binding curves were recorded on three mass sensitive cells operating in batch configurations: one commercial surface plasmon resonance (SPR) sensor and two custom-made Love wave surface-acoustic wave (LW-SAW) sensors. We obtained 3D plots depicting the time-evolution of the sensor response as a function of analyte concentration using real-time SPR binding sensograms. These “calibration” surfaces exploited the transient periods of the extended kinetic curves, prior to equilibrium, creating a “fingerprint” for each analyte, in considerably shortened time frames compared to the conventional 2D calibration plots. The custom-made SAW sensors operating in different experimental conditions allowed the detection of AFB1-protein carrier in the nanomolar range. Subsequent statistical significance tests were performed on unpaired data sets to validate the custom-made LW-SAW sensors.

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Kim, Eunhyun, Jinuk Kim, Seonggyun Ha, Changsik Song, and Joo-Hyung Kim. "Improved Performance of Surface Acoustic Wave Sensors by Plasma Treatments for Chemical Warfare Agents Monitoring." Journal of Nanoscience and Nanotechnology 20, no. 11 (November 1, 2020): 7145–50. http://dx.doi.org/10.1166/jnn.2020.18850.

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The effects of a plasma treatment on the sensing performance of surface acoustic wave (SAW) sensors to detect chemical warfare agents (CWAs) were investigated. SAW sensors designed for an operating frequency of 250 MHz were fabricated using lift-off techniques followed by the deposition of a very thin thiourea (TU) layer as a sensing film on the sensing area of the SAW sensor. To achieve some advantages from the plasma treatment on the surface, such as cleaning, surface activation and modification, a post-plasma treatment was performed on the sensing layer and the sensing performance of the SAW sensor was measured by a comparison with the measured responses, providing different simulant gases through the gas feeding system. The sensitivity test revealed significant improvement in the sensing ability of the SAW sensor to detect DMMP, a simulant of a CWA, but with a relatively longer recovery time. The responses of other simulants at different concentrations and different simulant vapors were compared. The results showed that a plasma treatment on the sensing layer of a SAW device can improve the selectivity and sensitivity to a certain target gas or some volatile organic compounds. Therefore, a plasma treatment will be very useful for improving the selectivity and sensitivity of SAW sensors for the detection of CWAs.

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Pan, Yong, Qin Molin, Tengxiao Guo, Lin Zhang, Bingqing Cao, Junchao Yang, Wen Wang, and Xufeng Xue. "Wireless passive surface acoustic wave (SAW) technology in gas sensing." Sensor Review 41, no. 2 (March 22, 2021): 135–43. http://dx.doi.org/10.1108/sr-03-2020-0061.

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Purpose This paper aims to give an overview about the state of wireless passive surface acoustic wave (SAW) gas sensor used in the detection of chemical vapor. It also discusses a variety of different architectures including delay line and array sensor for gas detection, and it is considered that this technology has a good application prospect. Design/methodology/approach The authors state the most of the wireless passive SAW methods used in gas sensing, such as CO2, CO, CH4, C2H4, NH3, NO2, et al., the sensor principles, design procedures and technological issues are discussed in detail; their advantages and disadvantages are also summarized. In conclusion, it gives a prospect of wireless passive SAW sensor applications and proposes the future research field might lie in the studying of many kinds of harmful gases. Findings In this paper, the authors will try to cover most of the important methods used in gas sensing and their recent developments. Although wireless passive SAW sensors have been used successfully in harsh environments for the monitoring of temperature or pressure, the using in chemical gases are seldom reported. This review paper gives a survey of the present state of wireless passive SAW sensor in gas detection and suggests new and exciting perspectives of wireless passive SAW gas sensor technology. Research limitations/implications The authors will review most of the methods used in wireless passive SAW sensor and discuss the current research status and development trend; the potential application in future is also forecasted. Originality/value The authors will review most of the methods used in wireless passive SAW sensor and discuss the current research status and development trend; the potential application in future is also forecasted.

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Hejczyk, Tomasz, Marian Urbańczyk, Tadeusz Pustelny, and Wiesław Jakubik. "Numerical and Experimental Analysis of the Response of a SAW Structure with WO3 Layers on Action of Carbon Monoxide." Archives of Acoustics 40, no. 1 (March 1, 2015): 19–24. http://dx.doi.org/10.1515/aoa-2015-0003.

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Abstract The paper presents the results of an analysis of gaseous sensors based on a surface acoustic wave (SAW) by means of the equivalent model theory. The applied theory analyzes the response of the SAW sensor in the steady state affected by carbon monoxide (CO) in air. A thin layer of WO3 has been used as a sensor layer. The acoustical replacing impedance of the sensor layer was used, which takes into account the profile of the concentration of gas molecules in the layer. Thanks to implementing the Ingebrigtsen equation, the authors determined analytical expressions for the relative changes of the velocity of the surface acoustic wave in the steady state. The results of the analysis have shown that there is an optimum thickness of the layer of CO sensor at which the acoustoelectric effect (manifested here as a change in the acoustic wave velocity) is at its highest. The theoretical results were verified and confirmed experimentally

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Zhang, Guigen. "Nanostructure-Enhanced Surface Acoustic Waves Biosensor and Its Computational Modeling." Journal of Sensors 2009 (2009): 1–11. http://dx.doi.org/10.1155/2009/215085.

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Surface acoustic wave (SAW) devices are considered to be very promising in providing a high-performance sensing platform with wireless and remote operational capabilities. In this review, the basic principles of SAW devices and Love-mode SAW-based biosensors are discussed first to illustrate the need for surface enhancement for the active area of a SAW sensor. Then some of the recent efforts made to incorporate nanostructures into SAW sensors are summarized. After that, a computational approach to elucidate the underlying mechanism for the operations of a Love-mode SAW biosensor with nanostructured active surface is discussed. Finally, a modeling example for a Love-mode SAW sensor with skyscraper nanopillars added to in its active surface along with some selected results is presented.

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Voinova, Marina V. "On Mass Loading and Dissipation Measured with Acoustic Wave Sensors: A Review." Journal of Sensors 2009 (2009): 1–13. http://dx.doi.org/10.1155/2009/943125.

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We summarize current trends in the analysis of physical properties (surface mass density, viscosity, elasticity, friction, and charge) of various thin films measured with a solid-state sensor oscillating in a gaseous or liquid environment. We cover three different types of mechanically oscillating sensors: the quartz crystal microbalance with dissipation (QCM-D) monitoring, surface acoustic wave (SAW), resonators and magnetoelastic sensors (MESs). The fourth class of novel acoustic wave (AW) mass sensors, namely thin-film bulk acoustic resonators (TFBARs) on vibrating membranes is discussed in brief. The paper contains a survey of theoretical results and practical applications of the sensors and includes a comprehensive bibliography.

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Muhammad, Fayyaz, and Hu Hong. "Sensing Magnetic Fields With Surface Acoustic Wave (SAW) Sensors." Journal of Magnetics 24, no. 3 (September 30, 2019): 518–29. http://dx.doi.org/10.4283/jmag.2019.24.3.518.

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Luo, Wei, Qui Yun Fu, Jian Lin Wang, Huan Liu, and Dong Xiang Zhou. "Accurate FEM/BEM Simulation of Wireless Passive Surface Acoustic Wave Sensors." Key Engineering Materials 368-372 (February 2008): 198–201. http://dx.doi.org/10.4028/www.scientific.net/kem.368-372.198.

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The wireless passive surface acoustic wave (SAW) impedance-loaded sensors offer new and exciting perspectives for remote monitoring and controlling of moving parts, even in harsh environments. However, the classical simulation models such as equivalent circuit model (ECM) and coupling of modes (COM) model are not rigorous enough for these sensors since these sensors usually work in the RF band. We try to make it more accurate by using FEM/BEM (combined finite element method and boundary element method) model to determine some key parameters used in the COM model of impedance-loaded SAW sensors. In this paper, we use periodic Green function which is the basis of FEM/BEM model to determine the key parameters. The result of measurements on real SAW is nearly in accordance with that of simulations.

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Durdaut, Phillip, Cai Müller, Anne Kittmann, Viktor Schell, Andreas Bahr, Eckhard Quandt, Reinhard Knöchel, Michael Höft, and Jeffrey McCord. "Phase Noise of SAW Delay Line Magnetic Field Sensors." Sensors 21, no. 16 (August 21, 2021): 5631. http://dx.doi.org/10.3390/s21165631.

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Surface acoustic wave (SAW) sensors for the detection of magnetic fields are currently being studied scientifically in many ways, especially since both their sensitivity as well as their detectivity could be significantly improved by the utilization of shear horizontal surface acoustic waves, i.e., Love waves, instead of Rayleigh waves. By now, low-frequency limits of detection (LOD) below 100 pT/Hz can be achieved. However, the LOD can only be further improved by gaining a deep understanding of the existing sensor-intrinsic noise sources and their impact on the sensor’s overall performance. This paper reports on a comprehensive study of the inherent noise of SAW delay line magnetic field sensors. In addition to the noise, however, the sensitivity is of importance, since both quantities are equally important for the LOD. Following the necessary explanations of the electrical and magnetic sensor properties, a further focus is on the losses within the sensor, since these are closely linked to the noise. The considered parameters are in particular the ambient magnetic bias field and the input power of the sensor. Depending on the sensor’s operating point, various noise mechanisms contribute to f0 white phase noise, f−1 flicker phase noise, and f−2 random walk of phase. Flicker phase noise due to magnetic hysteresis losses, i.e. random fluctuations of the magnetization, is usually dominant under typical operating conditions. Noise characteristics are related to the overall magnetic and magnetic domain behavior. Both calculations and measurements show that the LOD cannot be further improved by increasing the sensitivity. Instead, the losses occurring in the magnetic material need to be decreased.

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Constantinoiu, Izabela, and Cristian Viespe. "ZnO Metal Oxide Semiconductor in Surface Acoustic Wave Sensors: A Review." Sensors 20, no. 18 (September 8, 2020): 5118. http://dx.doi.org/10.3390/s20185118.

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Surface acoustic wave (SAW) gas sensors are of continuous development interest to researchers due to their sensitivity, short detection time, and reliability. Among the most used materials to achieve the sensitive film of SAW sensors are metal oxide semiconductors, which are highlighted by thermal and chemical stability, by the presence on their surface of free electrons and also by the possibility of being used in different morphologies. For different types of gases, certain metal oxide semiconductors are used, and ZnO is an important representative for this category of materials in the field of sensors. Having a great potential for the development of SAW sensors, the discussion related to the development of the sensitivity of metal oxide semiconductors, especially ZnO, by the synthesis method or by obtaining new materials, is suitable and necessary to have an overview of the latest results in this domain.

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Viespe, Dinca, Popescu-Pelin, and Miu. "Love Wave Surface Acoustic Wave Sensor with Laser-Deposited Nanoporous Gold Sensitive Layer." Sensors 19, no. 20 (October 16, 2019): 4492. http://dx.doi.org/10.3390/s19204492.

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Laser-deposited gold immobilization layers with different porosities were incorporated into Love Wave Surface Acoustic Wave sensors (LW-SAWs). Acetylcholinesterase (AChE) enzyme was immobilized onto three gold interfaces with different morphologies, and the sensor response to chloroform was measured. The response of the sensors to various chloroform concentrations indicates that their sensing properties (sensitivity, limit of detection) are considerably improved when the gold layers are porous, in comparison to a conventional dense gold layer. The results obtained can be used to improve properties of SAW-based biosensors by controlling the nanostructure of the gold immobilization layer, in combination with other enzymes and proteins, since the design of the present sensor is the same as that for a Love Wave biosensor.

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Joshi, S. G. "Surface-acoustic-wave (SAW) flow sensor." IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control 38, no. 2 (March 1991): 148–54. http://dx.doi.org/10.1109/58.68472.

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Kukaev, Alexander, Dmitry Lukyanov, Denis Mikhailenko, Daniil Safronov, Sergey Shevchenko, Vladimir Venediktov, and Andrey Vlasov. "Formation of a Complex Topologies of SAW-Based Inertial Sensors by Laser Thin Film Local Evaporation." Micromachines 12, no. 1 (December 24, 2020): 10. http://dx.doi.org/10.3390/mi12010010.

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Originally, sensors based on surface acoustic waves are fabricated using photolithography, which becomes extremely expensive when a small series or even single elements are needed for the research. A laser thin film local evaporation technique is proposed to substitute the photolithography process in the production of surface acoustic wave based inertial sensors prototypes. To estimate its potential a prototype of a surface acoustic wave gyroscope sensing element was fabricated and tested. Its was shown that the frequency mismatch is no more than 1%, but dispersion of the wave on small inertial masses leads to a spurious parasitic signal on receiving electrodes. Possible ways of its neglecting is discussed.

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Cao, Bing Qing, Qi Bin Huang, Yong Pan, and Mo Lin Qin. "The Respond Characteristic Property in Different Temperatures of SAW Sensor with p-tertbutylcalix[4]arene Coatings to Detect DMMP." Advanced Materials Research 1015 (August 2014): 590–93. http://dx.doi.org/10.4028/www.scientific.net/amr.1015.590.

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This paper presents new effective approachs for the supermolecule film deposition of surface acoustic wave (SAW) chemical sensors for detecting DMMP. 25-(thioalkyl-alkoxy)-p-tertbutylcalix [4] arene self-assembly molecular imprinted film as the sensitive film was coated on the gold delay line of SAW sensors to detect DMMP. The sensor has special response to organoosphorus compounds and the respond characteristic property in different temperatures of SAW sensor was studied in detail, had important reference value in counter-terrorism.

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Kahl, Jonathan, Vishal M. Dhagat, Devendra Kalonia, and Faquir C. Jain. "Characterization of a Protein Using Saw Resonator." International Journal of High Speed Electronics and Systems 23, no. 01n02 (March 2014): 1420006. http://dx.doi.org/10.1142/s0129156414200067.

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Surface Acoustic Wave (SAW) propagation on the surface of a piezoelectric crystal is used as a carrier of information. SAW Sensors are micro-electromechanical systems (MEMS) in which high frequency acoustic waves travel close to the surface of a piezoelectric substrate. Because of confined acoustic energy near the surface within the range of one acoustic wavelength, SAW devices are highly sensitive for surface perturbation such as molecular absorption or adsorption and change of viscoelastic properties. Surface acoustic wave (SAW) devices are very promising in providing a high-performance sensing platform with wireless and remote operational capabilities. Research focus is on studying methods to characterize conductance, susceptance, viscosity, and other properties of protein samples, like albumin using SAW related resonator devices quickly and inexpensively using quantities of less than one Nano-liter. Applied pressure or bending of the quartz sets up a condition where a separation of charge occurs (due to change in dipole moment density). The potential difference is proportional to the magnitude of stress. When a mass is deposited on the electrode the resultant decrease in resonant frequency can detect mass changes at nanogram level. We propose to advance the sensitivity of the characterization by use of quartz SAW resonators since they can operate at much higher frequency than bulk wave oscillators.

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Samarentsis, Anastasios G., Alexandros K. Pantazis, Achilleas Tsortos, Jean-Michel Friedt, and Electra Gizeli. "Hybrid Sensor Device for Simultaneous Surface Plasmon Resonance and Surface Acoustic Wave Measurements." Sensors 20, no. 21 (October 29, 2020): 6177. http://dx.doi.org/10.3390/s20216177.

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Surface plasmon resonance (SPR) and Love wave (LW) surface acoustic wave (SAW) sensors have been established as reliable biosensing technologies for label-free, real-time monitoring of biomolecular interactions. This work reports the development of a combined SPR/LW-SAW platform to facilitate simultaneous optical and acoustic measurements for the investigation of biomolecules binding on a single surface. The system’s output provides recordings of two acoustic parameters, phase and amplitude of a Love wave, synchronized with SPR readings. We present the design and manufacturing of a novel experimental set-up employing, in addition to the SPR/LW-SAW device, a 3D-printed plastic holder combined with a PDMS microfluidic cell so that the platform can be used in a flow-through mode. The system was evaluated in a systematic study of the optical and acoustic responses for different surface perturbations, i.e., rigid mass loading (Au deposition), pure viscous loading (glycerol and sucrose solutions) and protein adsorption (BSA). Our results provide the theoretical and experimental basis for future application of the combined system to other biochemical and biophysical studies.

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Kim, Jinuk, Eunhyun Kim, Jihyun Kim, Joo-Hyung Kim, Seonggyun Ha, Changsik Song, Won Jun Jang, and Jaesook Yun. "Four-Channel Monitoring System with Surface Acoustic Wave Sensors for Detection of Chemical Warfare Agents." Journal of Nanoscience and Nanotechnology 20, no. 11 (November 1, 2020): 7151–57. http://dx.doi.org/10.1166/jnn.2020.18851.

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Recently, efforts have been made to adapt surface acoustic waves (SAWs) for use in chemical sensors for detection of chemical warfare agents (CWAs). In this study, a four-channel real-time CWA detection system was constructed using four 250-MHz SAW sensors. Each system consists of three different chemical sensors and one reference sensor. The reference sensor compensates for frequency variations according to humidity and temperature conditions. Signals from the SAW sensors can be checked on a PC-based graphical user interface without additional measuring equipment. To measure dimethyl methylphosphonate (DMMP), a simulant of sarin gas, polyhedral oligomeric silsesquioxane (POSS) and thiourea (TU)-based synthetic polymers were used as sensing materials. The reference sensor was not coated, whereas the three different chemical sensors were coated with POSS, TU-1, and TU-2. The maximum frequencies of POSS, TU-1, and TU-2 were shifted 15.86, 13.85, and 0.944 kHz, showing significant values. We also found a relatively good linear relation between the frequency shift and the concentration of DMMP. The three sensing materials selected-POSS, TU-1, and TU-2-responded significantly to DMMP and triethylphosphate in the selectivity tests. This response is due to the chemical bonding of the sensing materials with the phosphonate in the nerve-agent simulants. These results indicate that the four-channel SAW monitoring system described in this paper shows potential as a portable real-time monitoring system to detect a variety of toxic vapors simultaneously, without using complex measuring equipment. In addition, this approach has demonstrated potential for developing excellent portable sensors to detect different types of CWAs.

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Attia, Ghada, Zineb Khaldi, Seyfeddine Rahali, Najla Fourati, Chouki Zerrouki, Rachida Zerrouki, Mahamadou Seydou, Nourdin Yaakoubi, and Rafik Ben Chaabane. "Design of Surface Acoustic Wave Sensors Functionalized with Bisphenol S Based Molecules for Lead Ions Detection." Proceedings 2, no. 13 (November 26, 2018): 872. http://dx.doi.org/10.3390/proceedings2130872.

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This study concerns the design of surface acoustic wave sensors functionalized with bisphenol S based molecules for lead ions detection. (4-hydroxyphenyl, 4′-benzyloxyphenyl) sulfone (M1), (4-hydroxyphenyl,4′-anthrylmethyloxyphenyl) sulfone (M2) and (4,4′-bis (anthrylmethyloxyphenyl)) sulfone (M3) were synthesized and then drop-coated on the SAWs sensing areas. Gravimetric results indicate that the limit of detection of the three sensors is in the picomolar range and that the M3/SAW sensor has the highest affinity towards lead ions compared to M1/SAW and M2/SAW. Density functional theory (DFT) calculations were investigated to support experimental results and to understand the nature of interactions involved between lead ions and the three synthetized molecules.

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Ten, Seng Teik, Uda Hashim, Ahmad Sudin, Wei Wen Liu, Kai Loong Foo, N. H. M. Salleh, Hashim Hisham, and T. Nazwa. "Modeling Development of a High-Sensitivity Escherichia coli O157:H7 Detection Based on SH SAW Sensor." Advanced Materials Research 925 (April 2014): 595–99. http://dx.doi.org/10.4028/www.scientific.net/amr.925.595.

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Surface acoustic waves based devices were initially developed for the telecommunication purpose such as signal filters and resonators. The acoustic energy is strongly confined on the surface of the surface acoustic waves (SAW) based devices and consequent their ultra-sensitivity to the surface perturbation. This has made SAW permits the highly sensitive detection of utterly diminutive charges on the surface. Hence, SAW based devices have been modified to be sensors. Food contamination has become critical issue and sensitive detection devices are needed urgently as small amount of harmful bacterial pathogens such as Escherichia coli (E.coli) O157:H7with the dose fewer than 100 organisms in food products or water is enough to cause serious gastrointestinal illness to human. Therefore, ultra-high sensitive, label free biosensors have been designed in this research for the low concentration E.coli detection. After the saturated development in telecommunication filed, SAW sensors were developed for gas detections and have been moving towards biological detections recently. Shear horizontal surface acoustic wave (SHSAW), one of the SAW based types is most suitable for the liquid based application as it has the advantage of acoustic energy is not being radiated into liquid. Therefore, SHSAW device has the potential to provide high-performance sensing platform in this research. There have been a lot of complicated theoretical models for the SAW devices development since 1960 as signal filters and resonators such as from delta function model, equivalent circuit model, to the current SAW models such as coupling-of-modes (COM) model, P-matrix model and finite element analysis (FEA) model. However, SHSAW device in this research is not meant for signal filter or resonators but used for surface sensing purpose, therefore the simplicity method of the modeling is presented in the paper for the E.coli detection sensor development.

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Constantinoiu, Izabela, Dana Miu, and Cristian Viespe. "Surface Acoustic Wave Sensors for Ammonia Detection at Room Temperature Based on SnO2/Co3O4 Bilayers." Journal of Sensors 2019 (May 19, 2019): 1–6. http://dx.doi.org/10.1155/2019/8203810.

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The selectivity of a SAW (surface acoustic wave) sensor, with a Co3O4 sensitive thin film for NH3 (ammonia) and the influence of SnO2 on its sensitivity, was studied. Thin films were deposited by pulsed laser deposition (PLD) on quartz SAW sensor substrates. Two sensors with different types of sensitive films were developed: a Co3O4 thin film sensor (S1) and a SnO2/Co3O4 thin film sensor (S2). The sensitive films were deposited in conditions which ensured a porous structure. The sensors were tested in the presence of three gases: NH3, methanol, and toluene. The selectivity of Co3O4 for NH3 was determined from the difference in the frequency shifts of the sensor for NH3 and for VOCs (volatile organic compounds). The positive influence of SnO2 on the sensitivity of sensor S2 was observed from the lower limit of detection (LOD) of this sensor and from the differences in frequency shifts between sensor S1 and sensor S2.

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Sadek, A. Z., D. Buso, A. Martucci, P. Mulvaney, W. Wlodarski, and K. Kalantar-zadeh. "Titanium Dioxide-Based64∘YXLiNbO3Surface Acoustic Wave Hydrogen Gas Sensors." Journal of Sensors 2008 (2008): 1–5. http://dx.doi.org/10.1155/2008/254283.

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Amorphous titanium dioxide (TiO2) and gold (Au) dopedTiO2-based surface acoustic wave (SAW) sensors have been investigated as hydrogen gas detectors. The nanocrystal-dopedTiO2films were synthesized through a sol-gel route, mixing a Ti-butoxide-based solution with diluted colloidal gold nanoparticles. The films were deposited via spin coating onto64∘YXLiNbO3SAW transducers in a helium atmosphere. The SAW gas sensors were operated at various temperatures between 150 and310∘C. It was found that gold doping onTiO2increased the device sensitivity and reduced the optimum operating temperature.

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Tian, Yahui, Honglang Li, Wencan Chen, Zixiao Lu, Wei Luo, Xihui Mu, and Litian Wang. "A Novel Love Wave Mode Sensor Waveguide Layer with Microphononic Crystals." Applied Sciences 11, no. 17 (September 1, 2021): 8123. http://dx.doi.org/10.3390/app11178123.

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Surface acoustic wave (SAW) sensors have been applied in various areas with many advantages, such as their small size, high sensitivity and wireless and passive form. Love wave mode sensors, an important kind of SAW sensor, are mostly used in biology and chemistry monitoring, as they can be used in a liquid environment. Common Love wave mode sensors consist of a delay line with waveguide and sensitive layers. To extend the application of Love wave mode sensors, this article reports a novel Love wave mode sensor consisting of a waveguide layer with microphononic crystals (PnCs). To analyze the properties of the new structure, the band structure was calculated, and transmission was obtained by introducing delay line structures and quasi-three-dimensional models. Furthermore, devices with a traditional structure and novel structure were fabricated. The results show that, by introducing the designed microstructure of phononic crystals in the waveguide layer, the attenuation was barely increased, and the frequency was shifted by a small amount. In the liquid environmental experiments, the novel structure with micro PnCs shows even better character than the traditional one. Moreover, the introduced microstructure can be extended to microreaction tanks for microcontrol. Therefore, this novel Love wave mode sensor is a promising application for combining acoustic sensors and microfluidics.

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Mazzamurro, Aurelien, Abdelkrim Talbi, Yannick Dusch, Omar Elmazria, Philippe Pernod, Olivier Bou Matar, and Nicolas Tiercelin. "Highly Sensitive Surface Acoustic Wave Magnetic Field Sensor Using Multilayered TbCo2/FeCo Thin Film." Proceedings 2, no. 13 (November 30, 2018): 902. http://dx.doi.org/10.3390/proceedings2130902.

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Over the last decades, the use of Surface Acoustic Waves (SAW) has emerged as a promising technology in many applications such as filters, signal processing but also sensors. We report the fabrication and the characterization of a SAW delay line magnetic field sensor using uniaxial multi-layered 14×[TbCo2(3.7nm)/FeCo(4nm)] nanostructured thin film deposited on Y36° Lithium Niobate (Figure 1a). The sensor shows an interesting dependency to a tunable bias magnetic field with different orientations relative to the easy axis. The obtained results are well explained using an equivalent piezo-magnetic model described in a previous work.

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Viespe, Cristian. "Surface Acoustic Wave Sensors Based on Nanoporous Films for Hydrogen Detection." Key Engineering Materials 605 (April 2014): 331–34. http://dx.doi.org/10.4028/www.scientific.net/kem.605.331.

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Surface Acoustic Wave Sensor is one of the most promising detection systems due tosmaller size, lower weight, power requirements and great sensitivity. It is known from the liter-ature that Pd and ZnO are the most promising materials for detecting hydrogen. A nanoporousPd and ZnO based layered SAW sensors have been developed and investigated for hydrogen,at room temperature. The sensors were of a delay line type (quartz substrate, 70 MHz cen-tral frequency). The nanoporous sensitive layer was directly deposited onto a quartz substrateusing a picosecond laser ablation method. Lasers with picosecond pulses or a high repetitionrate leads to major changes in the ablation process and implicit in the deposited lm struc-ture. Thus, using such a regime, at a certain ambient gas pressure, we have the advantage ofdirectly obtaining a nanoporous lm. The sensor performances (sensitivity, limit of detectionand response time), for a hydrogen concentration in synthetic air of 0.015 2 % were studied.For a concentration between 0.2 - 0.8 % hydrogen/synthetic airs, the response times was 15 -44 s and 6 - 27 s in case of Pd lms and ZnO respectively. Limit of detection was about 6.3times better at Pd sensors (50 ppm) than ZnO sensors (315 ppm).

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Miu, Dana, Ruxandra Birjega, and Cristian Viespe. "Surface Acoustic Wave Hydrogen Sensors Based on Nanostructured Pd/WO3 Bilayers." Sensors 18, no. 11 (October 26, 2018): 3636. http://dx.doi.org/10.3390/s18113636.

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The effect of nanostructure of PLD (Pulsed Laser Deposition)-deposited Pd/WO3 sensing films on room temperature (RT) hydrogen sensing properties of SAW (Surface Acoustic Wave) sensors was studied. WO3 thin films with different morphologies and crystalline structures were obtained for different substrate temperatures and oxygen deposition pressures. Nanoporous films are obtained at high deposition pressures regardless of the substrate temperature. At lower pressures, high temperatures lead to WO3 c-axis nanocolumnar growth, which promotes the diffusion of hydrogen but only once H2 has been dissociated in the nanoporous Pd layer. XRD (X-ray Diffraction) analysis indicates texturing of the WO3 layer not only in the case of columnar growth but for other deposition conditions as well. However, it is only the predominantly c-axis growth that influences film sensing properties. Bilayers consisting of nanoporous Pd layers deposited on top of such WO3 layers lead to good sensing results at RT. RT sensitivities of 0.12–0.13 Hz/ppm to hydrogen are attained for nanoporous bilayer Pd/WO3 films and of 0.1 Hz/ppm for bilayer films with a nanocolumnar WO3 structure. SAW sensors based on such layers compare favorably with WO3-based hydrogen detectors, which use other sensing methods, and with SAW sensors with dense Pd/WO3 bilayers.

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Ramakrishnan, N., Harshal B. Nemade, and Roy Paily Palathinkal. "Investigation on Resonance Effects of Closely Resonating Nano-Pillars Attached to SAW Resonator." Advanced Materials Research 403-408 (November 2011): 1183–87. http://dx.doi.org/10.4028/www.scientific.net/amr.403-408.1183.

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Surface acoustic wave (SAW) sensors form an important class of micro sensors in the microelecto mechanical systems (MEMS) family. Mass loading effect of a sensing medium is one of the prime sensing principles in SAW sensors. Recently we reported mass loading effect of high aspect ratio nano-pillars attached to a SAW resonator. We observed increase in resonance frequency of the SAW resonator in addition to the general mass loading characteristics. We concluded that when the resonance frequency of the pillar is equal to the SAW resonator frequency, the resonance frequency shift caused by mass loading of pillar tends to a negligible value. When such resonating pillars are used as sensing medium in SAW sensors, even a very small change in the dimension of the pillar will offer significant resonance frequency shift. Accordingly, high sensitive SAW sensors can be developed. However in practice it’s quite difficult to manufacture nano-pillars with accurate dimensions such that they resonate with SAW resonator. There is more probability that the pillars may closely resonate with SAW device and offer mass loading. In the present work we have extended our earlier work and performed finite element method (FEM) simulation to study the insight physics of the closely resonating pillars and their effects on acoustic wave propagating on SAW substrate. In this paper we present the discussion on the resonance effects of typical closely resonating pillars on resonance frequency spectrum of the SAW resonator and observations in the pressure wave at the contact surface of the pillar and SAW resonator substrate. It is observed that when the nano-pillars closely resonate with SAW resonator, the pillar oscillations combine with waves propagating in the substrate and introduce beat frequencies. The results and discussion of this paper adds additional information in designing SAW based coupled resonating systems.

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Chen, Zhenglin, Qiaozhen Zhang, Congcong Li, Sulei Fu, Xiaojun Qiu, Xiaoyu Wang, and Haodong Wu. "Geometric Nonlinear Model for Prediction of Frequency–Temperature Behavior of SAW Devices for Nanosensor Applications." Sensors 20, no. 15 (July 29, 2020): 4237. http://dx.doi.org/10.3390/s20154237.

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Surface acoustic wave (SAW)-based sensors have become highly valued for their use as nanosensors in industrial applications. Accurate prediction of the thermal stability is a key problem for sensor design. In this work, a numerical tool based on the finite element method combined with piezoelectric Lagrangian equations has been developed to accurately predict the thermal sensitivity characteristics of surface acoustic wave devices. Theoretical analysis for the geometric nonlinearity contributing to the frequency–temperature characteristic and material constants’ dependency on temperature were taken into consideration. The thermomechanical equilibrium equation built on the three-dimensional finite element method (3D-FEM) mesh node took mesh movement into account because thermal expansion was employed. The frequency–temperature characteristics of different SAW modes, including Rayleigh waves and leaky waves excited on a piezoelectric substrate of quartz or lithium tantalate, respectively, were calculated. The theoretical accuracy of the proposed numerical tool was verified by experiments.

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Constantinoiu, Izabela, and Cristian Viespe. "Development of Pd/TiO2 Porous Layers by Pulsed Laser Deposition for Surface Acoustic Wave H2 Gas Sensor." Nanomaterials 10, no. 4 (April 15, 2020): 760. http://dx.doi.org/10.3390/nano10040760.

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The influence of sensitive porous films obtained by pulsed laser deposition (PLD) on the response of surface acoustic wave (SAW) sensors on hydrogen at room temperature (RT) was studied. Monolayer films of TiO2 and bilayer films of Pd/TiO2 were deposited on the quartz substrates of SAW sensors. By varying the oxygen and argon pressure in the PLD deposition chamber, different morphologies of the sensitive films were obtained, which were analyzed based on scanning electron microscopy (SEM) images. SAW sensors were realized with different porosity degrees, and these were tested at different hydrogen concentrations. It has been confirmed that the high porosity of the film and the bilayer structure leads to a higher frequency shift and allow the possibility to make tests at lower concentrations. Thus, the best sensor, Pd-1500/TiO2-600, with the deposition pressure of 600 mTorr for TiO2 and 1500 mTorr for Pd, had a frequency shift of 1.8 kHz at 2% hydrogen concentration, a sensitivity of 0.10 Hz/ppm and a limit of detection (LOD) of 1210 ppm. SAW sensors based on such porous films allow the detection of hydrogen but also of other gases at RT, and by PLD method such sensitive porous and nanostructured films can be easily developed.

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Nicolay, Pascal. "Wireless and Passive SAW Devices, for Structural Health Monitoring Applications." Proceedings 4, no. 1 (November 14, 2018): 5. http://dx.doi.org/10.3390/ecsa-5-05734.

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Sezen, A. S., S. Sivaramakrishnan, S. Hur, R. Rajamani, W. Robbins, and B. J. Nelson. "Passive Wireless MEMS Microphones for Biomedical Applications." Journal of Biomechanical Engineering 127, no. 6 (July 8, 2005): 1030–34. http://dx.doi.org/10.1115/1.2049330.

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This paper introduces passive wireless telemetry based operation for high frequency acoustic sensors. The focus is on the development, fabrication, and evaluation of wireless, batteryless SAW-IDT MEMS microphones for biomedical applications. Due to the absence of batteries, the developed sensors are small and as a result of the batch manufacturing strategy are inexpensive which enables their utilization as disposable sensors. A pulse modulated surface acoustic wave interdigital transducer (SAW-IDT) based sensing strategy has been formulated. The sensing strategy relies on detecting the ac component of the acoustic pressure signal only and does not require calibration. The proposed sensing strategy has been successfully implemented on an in-house fabricated SAW-IDT sensor and a variable capacitor which mimics the impedance change of a capacitive microphone. Wireless telemetry distances of up to 5 centimeters have been achieved. A silicon MEMS microphone which will be used with the SAW-IDT device is being microfabricated and tested. The complete passive wireless sensor package will include the MEMS microphone wire-bonded on the SAW substrate and interrogated through an on-board antenna. This work on acoustic sensors breaks new ground by introducing high frequency (i.e., audio frequencies) sensor measurement utilizing SAW-IDT sensors. The developed sensors can be used for wireless monitoring of body sounds in a number of different applications, including monitoring breathing sounds in apnea patients, monitoring chest sounds after cardiac surgery, and for feedback sensing in compression (HFCC) vests used for respiratory ventilation. Another promising application is monitoring chest sounds in neonatal care units where the miniature sensors will minimize discomfort for the newborns.

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Yamanaka, Kazushi. "Ball SAW Sensors for Safety and Reliability of Fuel Cell Technologies." Key Engineering Materials 321-323 (October 2006): 48–52. http://dx.doi.org/10.4028/www.scientific.net/kem.321-323.48.

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Detection of hydrogen gas is a crucial task for establishing safety and reliability of fuel cells, a key technology for the environment and our society. However, hydrogen is difficult to detect and various hydrogen sensors have many drawbacks. Here we report a novel hydrogen gas sensor, the ball surface acoustic wave (SAW) sensor, using Pd or PdNi sensitive film. The ball SAW sensor is based on a novel phenomenon, diffraction-free propagation of collimated beam along an equator of sphere. The resultant ultra-multiple roundtrips of SAW makes it possible to achieve highest sensitivity among SAW sensors. Moreover, it enables to use a very thin sensitive film, and consequently the shortest response time (2s) was realized. In terms of the sensing range, it has the widest range of 10 ppm to 100 % among any hydrogen sensors including FET or resistivity sensors. The ball SAW sensor can be applied not only to hydrogen but also to any gasses and possibly to liquids.

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Journal articles on the topic 'Surface acoustic wave sensors (SAW)'

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