Acoustic Cloak based on Pentamode Material with Graded Microstructure

Acoustic cloak using anisotropic density or pentamode (PM) material is capable of concealing target from any detective acoustic wave. The pentamode material scheme is more promising due to its solid phase feature and broadband efficiency [1, 2]. However, perfect PM material in theory doesn’t have static stability, and therefore some imperfection in practically designed microstructure PM material (see Fig.1) is unavoidable [3, 4]. This imperfection is crucial for shielding effect of acoustic cloak using microstructure PM material. In this paper, we will examine the influence of PM microstructure on the cloaking efficiency. We have designed the first PM cloak with graded microstructure (see Fig.2) and investigated its wave steering ability through direct acoustic/solid coupling simulation with COMSOL Multiphysics. Total scattering cross section (TSCS), which accounts for the scattered pressure in all directions, is chosen to evaluate the cloaking effect quantitatively.