Recent development of artificially engineered metamaterial has significantly widened the range of acoustic responses found in nature. Propagation of elastic waves through such composite materials unveils many applications most of which are acoustic analogue of electromagnetic metamaterials. While holographic imaging using electromagnetic metamaterials is visually indistinguishable from original object, hologramic acoustic imaging is still in a trivial stage. In this article, a conceptual design of butterfly shaped engineered metamaterial consisting of an array of full ring resonators at multiple-length scales embedded in a polymer matrix is reported. Wave propagation in the proposed media is largely affected by the geometrical anisotropy and the anisotropic constituent materials. Introduction of local anisotropy made this engineered structure a suitable candidate for ultrasonic wave bifurcation and convergence. A numerical simulation confirms the negative refraction phenomenon near 37.3 kHz and explores the superlensing capability. Wave dispersion and transmission were analyzed, which showed the formation of acoustic image at a distance away from the source. While superlensing capability is found primarily in electromagnetic metamaterials, local anisotropy in this butterfly design causes negative refraction that results in acoustic hologramic image formation. As the negative refraction leads to a richness of diversified material properties, the proposed acoustic metamaterial will have important applications in biomedical devices, ultrasonic imaging, wave guiding and marine transportations.
Hossain Ahmed, Riaz Ahmed, and Sourav Banerjee, "Butterfly metamaterial for acoustic hologramic imaging through superlensing capability (Conference Presentation)," Proc. SPIE 10600, Health Monitoring of Structural and Biological Systems XII, 1060019 (Presented at SPIE Smart Structures and Materials + Nondestructive Evaluation and Health Monitoring: March 07, 2018; Published: 3 April 2018); https://doi.org/10.1117/12.2296630.5763102549001.
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