PerspectiveMaterials Science

Soft Acoustic Metamaterials

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Science  18 Oct 2013:
Vol. 342, Issue 6156, pp. 323-324
DOI: 10.1126/science.1241727

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Summary

Resonance phenomena occur with all types of vibrations or waves and may play a part in spectacular events, such as the collapse of structures—for example, the fall of the Broughton suspension bridge near Manchester in 1831 (1). Indeed, the oscillations of a structure submitted to harmonic excitation reaches its maximum amplitude at the resonance frequency ω0 of the system. At low driving frequencies (ω < ω0), its response is in phase with the forcing but becomes out of phase just beyond (ω0 < ω). Such an out-of-phase response has been exploited with “locally resonant materials” (2). The proposed strategy is to embed a large enough collection of identical mechanical resonators in a passive structure to control wave propagation. These features are used to reach unusual macroscopic behaviors such as ultradamping of noise or negative refraction for imaging (3).