Experimental Characterization of Two-Dimensional Tunable Metamaterials

A periodic array of shunted piezoelectric patches is used to produce a two-dimensional metamaterial with tunable properties. The proposed configuration exploits the waveguiding capabilities of a phononic crystal plate in conjunction with a periodic arrangement of eight surface-bonded PZT disks. Each piezo transducer is connected to an independent resistive-inductive network, so that the system features an internal resonance that occurs at the tuning frequency of the shunting circuits. The dispersion relations of the resulting metamaterial are experimentally estimated through detailed mappings of the wavefield measured using a scanning laser doppler vibrometer. Experimental results indicate that the coupled system features a band structure behavior induced by the internal resonance of the electrical networks, and suggest the possibility to alter the waveguiding properties of the considered metamaterial without modifying the physical structure of the phononic crystal plate.