SAW Resonator Based Chemical Toxic Agent Sensors

As much attention has been paid to chemical weapons in all over the world, many countries such as USA and the Netherlands have put a lot of manpower and resource in researching the toxic agents sensors, or even several of these countries have equipped the sensors in battlefield and anti-terrorism. However, surface acoustic wave (SAW) based chemical sensors to detect chemical agents in the domestic research is only in its infancy. Particularly, there is a great requirement in improving the sensitivity, stability and response time.This paper firstly researches the characteristics of the sensitive polymer membrane, the choosing a suitable gas-sensitive membrane coating materials, and the location on the SAW resonators. A Van dyke model is established to analyze the impacts of membrane’s thickness and viscoelasticity on chemical agent sensors. The results show that: On one hand, as the membrane’s thickness increase, acoustic attenuation deteriorate, Furthermore, if the thickness increases to some extent, the SAWR may refuse to oscillate. On the other hand, viscosity of membrane result in the non-linear sensitivity.Another focus of this research is to design a detecting circuit with high-frequency stability, which includes: matching network, phase compensation network, selecting frequency network, attenuation network, temperature compensation circuit, mixer, as well as low-pass filter circuit . In this section, we describe all networks above in details such as the advantages,disadvantages of the networks and how to choose the reasonable design. In order to enhance the frequency stability, this paper concisely present some optimized measures which we should make emphasis on.Finally, we did experiments on the sensor by exposing it to Sarin agent, a 315-MHz dual SAW resonator and hyperbranched polymer film were applied. Experiments show that: the sensitivity of the sensor can be initially achieved 3KHz mg L, the response time is 50 s, recovery time is about 60 s .