Bubble Architectures for Locally Resonant Acoustic Metamaterials

Soft acoustic metamaterials that embed soft materials in a host media have promising applications in aqueous environments. However, the preparation of soft metamaterials under water and realization of low-frequency soft acoustic metamaterials remains a challenge. By combining 3D printing technology and surface hydrophobic properties, this work presents a general approach to construct 3D soft acoustic metamaterials using bubbles as resonator units. Low-frequency broadband locally resonant metamaterials can be realized using patterned bubbles with bandgaps that are orders of magnitude wider than other locally resonant metamaterials. In addition, a water-to-air ultratransmission metasurface is prepared by patterning a layer of bubbles beneath the water surface, which allows for the ultratransmission of sound across an air–water interface. This strategy opens up promising avenues for many applications based on locally resonant metamaterials such as deep subwavelength acoustic superlenses or negative-refraction metamaterials.