Negative Refraction Acoustic Lens Based on Elastic Shell Encapsulated Bubbles

Advanced devices for acoustic negative refraction and cloaking can be achieved by utilizing acoustic metamaterials. However, the capacities of acoustic metamaterials often are weakened or even disappear when considering thermoviscous loss and damping, which limits the applications of metamaterials. Here, the negative refraction and acoustic imaging capacity of acoustic metamaterials that are comprised of 2D underwater elastic shell encapsulated bubble arrays numerically and experimentally is verified. The influence of thermoviscous loss and damping in solid structures on imaging is discussed. The transmission loss can be reduced by structural optimization. Accordingly, focusing of the sound emitted by a point source is achieved using a flat metamaterial slab whose effective refractive index is −1, which is promising for underwater acoustic imaging.