Comparison of piezoceramic, piezopolymer and single crystal materials for use in micromachined bimorph structures

Miniature bimorph and unimorph structures provide a novel approach to the generation of ultrasonic signals in a gaseous medium such as air. It is shown that such devices can be constructed from piezoceramic, piezopolymer and single crystal materials. Fabrication involves the use of a micromachining system based on a copper vapour laser. The fundamental wavelength of this laser is 511nm, however its versatility is greatly enhanced by the utilisation of a frequency-doubling cell that facilitates operation at ultraviolet wavelengths. It is shown that the performance of a device fabricated form any one of the previously mentioned materials can be accurately predicted using mutually consistent displacement and natural frequency equations that are the product of a recently developed theory.