Surface acoustic waves at solid-liquid boundaries and their application in sensors and actuators

Since the invention of the interdigital transducer [1], surface acoustic waves have been utilized in sensors and actuators for numerous applications [2]. This lecture is focussed on the interaction of surface acoustic waves with liquid coverings and the corresponding effect of mode conversion [3]. Surface acoustic wave sensor devices operable in liquids will be described, putting particular emphasis on acoustic waveguide sensors and their applications to the characterization of liquids, force measurements and deposition layer detection [4]. In addition, a propulsive momentum can be transferred to a covering liquid by a propagating surface acoustic wave. Examples of this phenomenon called acoustic streaming both in microscopic [5] as well as in macroscopic [6] dimensions will be presented.

1. White R M, Proc. IEEE 58 (1970) 1238-1276
2. Ballantine D S, White R M, Martin S J, Ricco A J, Zellers E T, Frye G C and Wohltjen H 1977: Acoustic Wave Sensors (New York: Academic)
3. Lindner G, J. Phys. D: Appl. Phys. 41 (2008) 123001-123015
4. Lindner G, Faustmann H, Frankenberger S, Münch M, Pflaum K, Rothballer S and Unterburger M, Proc. IEEE Ultrasonic Symp. 2006, 1181-1184
5. Wixforth A, Superlattices and Microstructures 33 (2003) 389-396
6. Lindner G, Faustmann H, Fischer T, Krempel S, Münch M, Rothballer S and Schmitt M, Proc. IEEE Ultrasonic Symp. 2007, 2331- 2334

Excitation burst and receiver signal in a liquid filled acoustic waveguide sensor based on mode conversion of Lamb waves