INTRODUCTORY LECTURE - ACOUSTIC INTERACTIONS FROM FARADAYS CRISPATIONS TO MEMS

In an 1831 paper, Michael Faraday described observations cf the intera ction of a vibrating solid with a liquid supported by the solid. The m otions induced on the surface of the liquid, which he termed crispatio ns, resulted from the creation of capillary waves, which are still a s ubject of research. The contributions to the present Faraday Discussio n concern chiefly the use of piezoelectric crystals to study the prope rties of films and of liquids at liquid/solid interfaces. In this Intr oductory Lecture, the characteristics of piezoelectric acoustic device s used for sensing are reviewed and contrasted. Recent developments in the fabrication of micromechanical structures to make microelectromec hanical systems (MEMS) are reviewed. Some applications of this technol ogy to make ultrasonic piezoelectric devices that sense and actuate li quids and gases are described.