Sharkskin-Inspired Magnetoactive Reconfigurable Acoustic Metamaterials

Abstract

<jats:p>Most of the existing acoustic metamaterials rely on architected structures with fixed configurations, and thus, their properties cannot be modulated once the structures are fabricated. Emerging active acoustic metamaterials highlight a promising opportunity to on-demand switch property states; however, they typically require tethered loads, such as mechanical compression or pneumatic actuation. Using untethered physical stimuli to actively switch property states of acoustic metamaterials remains largely unexplored. Here, inspired by the sharkskin denticles, we present a class of active acoustic metamaterials whose configurations can be on-demand switched via untethered magnetic fields, thus enabling active switching of acoustic transmission, wave guiding, logic operation, and reciprocity. The key mechanism relies on magnetically deformable Mie resonator pillar (MRP) arrays that can be tuned between vertical and bent states corresponding to the acoustic forbidding and conducting, respectively. The MRPs are made of a magnetoactive elastomer and feature wavy air channels to enable an artificial Mie resonance within a designed frequency regime. The Mie resonance induces an acoustic bandgap, which is closed when pillars are selectively bent by a sufficiently large magnetic field. These magnetoactive MRPs are further harnessed to design stimuli-controlled reconfigurable acoustic switches, logic gates, and diodes. Capable of creating the first generation of untethered-stimuli-induced active acoustic metadevices, the present paradigm may find broad engineering applications, ranging from noise control and audio modulation to sonic camouflage.</jats:p>

Fabricating and Assembling Acoustic Metamaterials and Phononic Crystals

“…[137] Using FDM-printed molds, magnetoactive sharkskin-inspired AMMs were fabricated and magnetically configured into acoustic logic gates (Figure 5d). [138] The same limitations in 3D printing technologies apply when printing a mold, directly affecting the cast structure. For example, a 3D-printed mold with a poor surface finish would likely cast an object with a nonuniform surface profile.…”

“…Figure shows an (i) AND gate and (ii) OR gate. Reproduced under terms of the CC-BY license [138]. Copyright 2020, The Authors, published by AAAS.…”

Magttice: a lattice model for hard-magnetic soft materials

“…Hard-magnetic soft materials, usually made by embedding hard magnetic neodymium-iron-boron (NdFeB) microparticles into soft matrix-like silicone elastomers, have attracted great attention due to their various remarkable features such as the response to remote external stimuli, fast actuation, excellent flexibility, and stretchability. [1][2][3][4][5][6][7] Promising applications include soft robotics, [8][9][10][11][12][13][14] machines and actuators, [15][16][17][18][19][20] microfluidics, [21][22][23][24][25] biomedical devices 10,13,14,[26][27][28][29][30] (e.g., endovascular neurosurgery 10 and smart catheters 29 ), and multifunctional architected materials and metastructures, 8,25,[31][32][33][34][35][36][37] just to name a few. The rapid developments of the field also call for efficient and accurate modeling and simulation platforms to rationalize the design, because these smart structures usually undergo very large and nonlinear de...…”

“…Among various numerical techniques, [32][33][34][35][36][37][38][39] finite element methods (FEMs) are widely used to simulate the nonlinear and active deformation of ferromagnetic materials. 32,39 For example, Zhao et al 32 derived a finite element simulation scheme for the hardmagnetic soft materials and implemented it into the FEM software ABAQUS through a user-defined element (UEL).…”

Metamaterial Acoustics on the (2 + 1)D Einstein Cylinder

“…For recent remarkable advances in this field of metamaterials acoustic, we refer to [11], where a special type of multifunctional acoustic lens is designed by only using isotropic material parameters. Furthermore, in [12], acoustic metamaterial devices are constructed that are reconfigurable by using untethered physical stimuli, i.e., avoiding mechanisms such as compression or pneumatic actuators.…”