Recent Developments in Surface Acoustic Wave (SAW) Sensors and Their Applications in Different Areas

Abstract

AbstractNowadays, chemical sensors are used in detecting the presence of certain gases and even liquid analytes. Due to the recent researches in the area of chemical sensors, their sensitivity, reliability and environmental stability are improving. This is due to the improvements in the two components (receptors and transducers) of the sensors. This paper is a critical review of recent advancements in chemical sensors, particularly the surface acoustic wave (SAW) sensors. SAW sensors are attracting researchers due to their short detection time, high sensitivity and high reliability. Metal oxide semiconductors are important option for preparing a sensitive film of SAW sensors. The film prepared from metal oxide semiconductors also has high thermal and chemical stability; one example is ZnO which can be used for making the film of SAW sensors for detecting different types of gases. The use of pulsed laser deposition (PLD) for depositing sensitive porous films has increased the ability of SAW sensors to detect different gases at very low concentrations. Monolayer films of TiO2 and bilayer films of Pd/TiO2 deposited on quartz substrates of SAW sensors are the examples of this. Considerable improvement in the sensing properties is observed when porous gold layers are used in place conventional dense gold layer. Nowadays, high-temperature SAW sensor (based on ZnO films) is developed which can work at high temperature (as high as 850 °C) with good stability. These high temperature gas sensors would be useful in engines and combustion system. There is a broad spectrum of SAW sensors which have a variety of uses ranging from detection of small gas molecules to large bio-molecules or sometimes even the whole cell structures.KeywordsChemical sensorsSAW sensorsMetal oxide semiconductorsPLDPorous gold layersThermal stabilityChemical stability