Adaptive GRIN lens based on piezoelectric metamaterial for acoustic beam focusing

Abstract

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.

Electroelastic metasurface with resonant piezoelectric shunts for tunable wavefront control

“…Inductive and resistive loads in the piezoelectric-shunt circuit were first proposed by Hagood and von Flotow [6] to enhance the vibration suppression performance of the piezoelectric metastructure. Later, other piezoelectric shunts with inductance and negative capacitance were explored to design electromechanical MMs and phononic crystals, which exhibited unconventional behaviors such as tunable bandgap and dispersive properties [7], leading to diverse applications including sound/vibration mitigation [10][11][12][13], energy harvesting [14,15], wave directivity manipulators [16][17][18][19][20], adaptive gradient index (GRIN) lens [21,22] and multifunctional designs [15,[23][24][25].…”

Passive discrete lens for broadband elastic guided wave focusing

“…Besides, by coupling the strategies as varying simultaneously the filling fraction of a Phononic Crystal Lens and the thickness of the plate it seems possible to control not only the lowest-order antisymmetric Lamb Mode ( 0 ) in a plate as classically done, but to consider broadband multimodal control focusing on the two lower order Lamb Modes ( 0 and 0 ) (Jin et al 2015). Finally, semi-active, active or adaptive strategies utilize multiphysic coupling such as electromechanical or thermomechanical to control wave propagation (Yi et al 2019;Billon et al 2019), and have allow to develop lenses for wave focusing (Chiou et al 2014;Yi et al 2016;Xu et al 2017).…”