Phononic crystals are created by periodic arrays of elastic structures displaying a strong contrast in their elastic properties and density. These materials can be arranged into one-dimensional (1D), 2D and 3D structures. The interest in phononic crystals has been generated by their unique properties such as the formation of band-gaps, near zero group velocity, and anomalous dispersion (negative refraction). These properties make phononic crystals a viable choice for use in the design and implementation of components for Radio Frequency Micro-Electro- Mechanical Systems (RF MEMS) including filters, resonators, and advanced signal processing functions. Nevertheless, one of the major stumbling block to the application of phononic crystals is the lack of practical frequency tunability of their properties.

During the presentation, the feasibility of contactless tunability of the band structure of two-dimensional bulk, SAW and Lamb waves phononic crystals will be demonstrated by employing magnetostrictive materials and applying an external magnetic field. Applications to tunable selective frequency filters with switching functionality, to reconfigurable wave-guides, demultiplexing devices and magnetic field sensors will be shown.

A second way to tune the band-gaps of a phononic cristal by using the nonlinear elastic properties of the materials will also be numerically demonstrated. The considered nonlinear phononic crystal, consisting of a one-dimensional set of steel inclusions in a silica matrix, shows elastic bistable switching capability.

Note : slides en anglais et présentation en français