Due to the attractive potential in elastic wave attenuation and wave guiding, acoustic metamaterials have received
much attention. Different from the more conventional metamaterials that possess only mechanical
displacement/deformation, the electro-mechanical metamaterials analyzed in this paper utilize the two-way electromechanical
coupling of piezoelectric transducers and local resonance induced by LC (inductor-capacitor) shunt circuits,
which features enlarged design space as well as adaptivity. We report an adaptive piezoelectric gradient index (GRIN)
lens featuring focusing acoustic wave. The proposed GRIN lens is comprised of arrayed piezoelectric unit-cells with
individually connected inductive shunt circuits. Taking advantage of wave velocity shifting in the vicinity of local
resonant frequency of unit-cell and specifically arranged LC shunt circuits, we can focus the transverse wave adaptively
by adjusting the inductive loads, i.e., tuning the inductances. Analytical investigations and finite element simulations
are performed. This tunable GRIN lens can be used as acoustic metamaterial for various acoustic devices operating
with broadband frequencies.
Jiawen Xu, Shilong Li, and J. Tang, "Adaptive GRIN lens based on piezoelectric metamaterial for acoustic beam focusing," Proc. SPIE 10164, Active and Passive Smart Structures and Integrated Systems 2017, 101641S (Presented at SPIE Smart Structures and Materials + Nondestructive Evaluation and Health Monitoring: March 29, 2017; Published: 17 April 2017); https://doi.org/10.1117/12.2260341.
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