Acoustic meta-atom with maximum Willis coupling
arXiv:1812.02318 · doi:10.1038/s41467-019-10915-5
Abstract
Acoustic metamaterials are structures with exotic acoustic properties, having promising applications in acoustic beam steering, focusing, impedance matching, absorption and isolation. Recent work has shown that the efficiency of many acoustic metamaterials can be enhanced by controlling an additional parameter known as Willis coupling, which is analogous to bianisotropy in electromagnetic metamaterials. The magnitude of Willis coupling in an acoustic meta-atom has been shown theoretically to have an upper limit, however the feasibility of reaching this limit has not been experimentally investigated. Here we introduce a meta-atom with Willis coupling which closely approaches this theoretical limit, that is much simpler and less prone to thermo-viscous losses than previously reported structures. We perform two-dimensional experiments to measure the strong Willis coupling, supported by numerical calculations. Our meta-atom geometry is readily modeled analytically, enabling the strength of Willis coupling and its peak frequency to be easily controlled. Together with its ease of fabrication, this will facilitate the design of future high efficiency acoustic devices.
arXiv comment16 pages, 6 figures
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- Discrete One-dimensional Models for the Electromomentum Coupling
- Acoustic resonators: symmetry classification and multipolar content of the eigenmodes
- Acoustic Lateral Recoil Force and Stable Lift of Anisotropic Particles
- Cloaking in-plane elastic waves with swiss rolls
- Radiation forces and torques in optics and acoustics
- Overall dynamic properties of locally resonant viscoelastic layered media based on consistent field integration for oblique anti-plane shear waves
- Exceptional points in single open acoustic resonator due to the symmetry breaking
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- Willis elasticity from microcontinuum field theories: Asymptotics, microstructure-property relationships, and cloaking