Practical Aspects of Acoustic-Wave Sensors

The previous chapters have provided the essential theoretical underpinnings of the functioning and interactions of acoustic-wave (AW) sensors, along with specific examples of how these devices have been used for chemical analysis and materials characterization. This chapter offers some details about the practical aspects of designing both the sensors and the systems that permit one to obtain the physicochemical information that AW sensors can provide. 

The first practical problem to be addressed is the fabrication of acoustic-wave sensor devices. While some devices are commercially available (see Appendix D), a researcher may need a unique device in order to investigate some previously unexplored aspect of AW sensors and their interactions with their environment. It is therefore quite valuable to understand basic device configurations, fundamental design principles, the different properties of the range of materials that can serve as device substrates, fabrication practices, and coating technologies. These issues are addressed in Section 6.2. 

Copyright 1997 by Academic Press All rights of reproduction in any form reserved. 

Yet another significant challenge to the successful use of AW sensors is the isolation of their sensitivities to numerous different perturbations, so that only a single, desired interaction is observed. As an example, AW sensors are sensitive to enviixmmental variables such as temperature, pressure, and gas or liquid flow rate in mass-sensing applications, excessive response to these variables can be a serious problem. Controlling the AW sensor environment is the focus of Section 6.4. 

Once the device has been fabricated, the chemically sensitive coating applied, and the supporting RF electronics turned on, acoustic-wave sensors sometimes do not perform as expected or desired. Drift may be excessive sensitivity or selectivity may be inadequate to solve the immediate problem. Section 6.5 outlines several popular strategies for enhancing AW sensor performance through careful system design. 

---