Alteration of Poisson´s ratio in high coupling piezoelectrics

Poisson´s ratio finds application in a number of areas of applied elasticity and solid mechanics, for example, to quantify the mechanical coupling between various vibrational modes. The gamut of future high-tech applications, e.g., resonant microstructures integrated with electronic and optical circuitry, can be extended by providing a dynamic mechanism for electrical adjustment of this quantity. This requires an extension of the usual Poisson´s ratio considerations to include the piezoelectricity of anisotropic substances. For piezoelectric materials, the Poisson´s ratios vary with orientation. This variability is to be expected. What is surprising is the size of the variability that can be produced via the piezo-effect by altering electrical boundary conditions in substances with strong piezocoupling, e.g., poled electroceramics. This second source of adjustment appears an attractive means of tuning novel MEMS filter and resonator devices for future cellular communications. This paper describes how both forms of variation come about: the angular changes, and how these are modified by the piezoelectric effect when electrical loads are imposed. Numerical examples are given.