Surface acoustic wave gas sensors

IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 2000

We report finite element simulations of the effect of conductive sensing layers on the surface wave velocity of langasite substrates. The simulations include both the mechanical and electrical influences of the conducting sensing layer. We show that three-dimensional simulations are necessary because of the out-of-plane displacements of the commonly used (0, 138.5, 26.7) Euler angle. Measurements of the transducer input admittance in reflective delay-line devices yield a value for the electromechanical coupling coefficient that is in good agreement with the threedimensional simulations on bare langasite substrate. The input admittance measurements also show evidence of excitation of an additional wave mode and excess loss due to the finger resistance. The results of these simulations and measurements will be useful in the design of surface acoustic wave gas sensors.

Proceedings of IEEE Sensors 2003 (IEEE Cat. No.03CH37498), 2003

The development of inexpensive and miniaturized Surface Acoustics Wave (SAW) gas sensors that are highly selective and sensitive is described. These sensors are implemented with micro-electro-mechanical systems (MEMS) in CMOS technology. IDT equivalent circuit and model for SAW delay line is introduced. Simulation results are included for characterization and design of the sensor. In this paper we will describe the design and post-processing steps to implement SAW device in CM,OS technology. Design parameters of this device were obtained using modeling equivalent circuit to characterize sensor. Two approaches were used in the design of the SAW gas sensor that will be discussed. A CMOS chip was fabricated using MOSIS. Thin film ZnO was grown on Silicon based die and its characterizations is presented.

2018 IEEE SENSORS, 2018

2005

Presented here are the results concerning investigations of thin vacuum-evaporated polyaniline layers as a toxic gas sensor in a Surface Acoustic Wave (SAW) system. The investigations were performed with different concentrations of the following toxic gases: NO2, SO2, CO, H2S and hydrogen in synthetic dry air. These thin films were formed in one of the dual delay line systems on a LiNbO3 Y-cut Zpropagation substrate, while the other one serves as a reference, permitting an easy detection of the arising differential frequency. SAW are very attractive due to their remarkable sensitivity in a specific configuration of the sensor structure, as well as their small size, low power consumption and frequency measurements. In such a sensor structure we can use both the acoustoelectric interaction (between the electric potential associated with surface wave and the charge carrier in the polyaniline film) and the mass effects. The sensor was tested in a computer-controlled system. Gases were m...

Handbook of Research on Nanoelectronic Sensor Modeling and Applications

Industrial activities have polluted the atmosphere very rapidly in these days. There are a various varieties of air pollutants having a strong effect on human health as well as on climate and specially environment, such as nitrogen dioxide (NO 2), oxides of carbon (CO x) and hydrocarbons. The World Health Organization (WHO) estimates that each year about 4.6million people die directly from causes of air pollution that will be a serious threat to human health. Therefore, there is a growing demand towards highly sensitive, cheap, low consumption, user-friendly devices which could monitor the quality of air indoor and outdoor areas for protecting human health. It is proved to be an efficient and economically feasible alternative for measuring different gas concentrations.

Archives of Acoustics, 2018

Detection and identification of toxic environmental gases have assumed paramount importance precisely in the defense, industrial and civilian security sector. Numerous methods have been developed for the sensing of toxic gases in the environment ever since surface acoustic wave (SAW) technology came into existence. Such SAW sensors called electronic nose (E-Nose) sensor use the frequency response of a delay line/resonator. SAW device is focused and given importance. The selective coating between input and output interdigital transducers (IDTs) in the SAW device is responsible for corresponding changes in operating frequency of the device for a specific gas/vapour absorbed from the environment. A suitable combination of well-designed SAW delay lines with selective coatings not only help to improve sensor sensitivity and selectivity but also leads to the minimization of false frequency alarms in the E-Nose sensor. This article presents a comprehensive review of design, development, si...

2012

Surface acoustic wave (SAW) gas sensors based on carbon nanotube polymer composites as sensitive layers were investigated for the detection of low concentrations of volatile organic compounds as octane and toluene. Several nanocomposites based on polyepichlorohydrin (PECH) and polyetherurethane (PEUT) with different percentage of multiwalled carbon nanotubes (MWCNT) were tested to study the effect of MWCNTs in the response of sensors.

Sensors and Actuators B …, 1995

ZnO-on-Si surface acoustic wave (SAW) delay lines have been examined as detectors of some combustible gases (CO, NO, H2), reactive gas such as O2 and other gases (CH4, N2, Ar). Measurements have been performed at temperatures of 20–160° C, operation ...

Progresses in Chemical Sensor, 2016

Online real-time monitoring of gases requires a miniaturized, passive, and accurate gas sensor. Surface acoustic wave (SAW) devices possess these properties which make them suitable for gas-sensing applications. They have shown remarkable results in sensing of different gases in terms of sensitivity, selectivity, response, and recovery times. One of the important prerequisites a designer should know is to have knowledge on the different types of sensing material suitable for gas-sensing applications, prior to design and fabrication of the sensor. Different sensing materials, including metal oxides, polymers, carbon nanotubes, graphene, nanocomposites, etc. have been used for SAW gas sensors. In this article, different sensing materials for SAW gas sensors will be discussed.

Sensors

In this paper, we present an overview of the latest achievements in surface acoustic wave (SAW) sensors for gas or liquid fluid, with a focus on the electrodes’ topology and signal processing, as related to the application of the sensing device. Although the progress in this field is mainly due to advances in the materials science and the sensing coatings, the interdigital (IDT) electrodes’ organization is also an important tool for setting the acoustic-wave-distribution mode, and, thus, for improvement of the SAW performance. The signal-conditioning system is of practical interest, as the implementation of the SAW, as a compact and mobile system is dependent on this electronic circuit. The precision of the detection of the SAW platform is related not only to the IDT electrodes’ geometry but also to their location around the sensing layer. The most commonly used architectures are shown in the present paper. Finally, we identify the needs for the future improvement of these prospecti...