This proposal is concerned with ultrasonic Lamb waves, which are elastic waves that propagate in plates of finite thickness. Our interest in these waves has been stimulated by the developments of the last 2-3 years during which Lamb wave devices have been successfully fabricated on plates that are thinner than 1 um. Waves propagating in such thin structures possess a number of attractive features for use in physical, chemical, and biological sensors. Lamb waves also provide a convenient tool for measuring the elastic properties of self-supporting thin films and microminiature mechanical structures. The aim of this project is to carry out theoretical and experimental investigation of the generation and detection of Lamb waves. Four different device configurations will be considered. These are: (1) piezoelectric plate excited by surface electrodes, (2) composite membrane consisting of piezoelectric film deposited on a nonpiezoelectric plate, (3) electrostrictive excitation in a nonpiezoelectric plate, and (4) excitation of Lamb waves in a nonpiezoelectric plate using surface stress sources. Results obtained from theoretical analysis will be experimentally verified. Besides enabling us to completely characterize a given transducer, the proposed research will also lead to the design of more efficient Lamb wave transducers.
