Multifunctional Acoustic Device Based on a Phononic Crystal with Independently Controlled Asymmetric Rotating Rods
Hyeonu Heo, Arkadii Krokhin, Arup Neogi, Zhiming Cui, Zhihao Yuan, Yihe Hua, Jaehyung Ju, Ezekiel Walker
Abstract
A reconfigurable phononic crystal (PnC) is proposed where elastic properties can be modulated by rotation of asymmetric solid scatterers immersed in water. The scatterers are metallic rods with a cross section of ${120}^{\ensuremath{\circ}}$ circular sector. Orientation of each rod is independently controlled by an external electric motor that allows continuous variation of the local scattering parameters and dispersion of sound in the entire crystal. Due to asymmetry of the scatterers, the crystal band structure possesses highly anisotropic band gaps. Synchronous rotation of all the scatterers by a definite angle changes the regime of reflection to the regime of transmission and vice versa. The same mechanically tunable structure functions as a gradient index medium by incremental, angular reorientation of rods along both row and column, and, subsequently, can serve as a tunable acoustic lens, an acoustic beam splitter, and finally an acoustic beam steerer.