An elasto-mechanical unfeelability cloak made of pentamode metamaterials

Abstract

Metamaterial-based cloaks make objects different from their surrounding appear just like their surrounding. To date, cloaking has been demonstrated experimentally in many fields of research, including electrodynamics at microwave frequencies, optics, static electric conduction, acoustics, fluid dynamics, thermodynamics and quasi two-dimensional solid mechanics. However, cloaking in the seemingly simple case of three-dimensional solid mechanics is more demanding. Here, inspired by invisible core-shell nanoparticles in optics, we design an approximate elasto-mechanical core-shell 'unfeelability' cloak based on pentamode metamaterials. The resulting three-dimensional polymer microstructures with macroscopic overall volume are fabricated by rapid dip-in direct laser writing optical lithography. We quasi-statically deform cloak and control samples in the linear regime and map the displacement fields by autocorrelation-based analysis of recorded movies. The measured and the calculated displacement fields show very good cloaking performance. This means that one can elastically hide objects along these lines.

Reexamining the mechanical property space of three-dimensional lattice architectures

“…Incorporating three-dimensional architecture into materials design across multiple length scales has led to the creation of advanced materials with novel mechanical properties, such as ultralight weight [1][2][3], negative Poisson's ratios [4,5], and near infinite bulk-to-shear modulus ratios [6,7]. The versatility of current fabrication methods and processing techniques engenders a virtually unbounded potential design space by which new materials can be created [8][9][10][11][12][13][14][15][16][17].…”

Microlattice Metamaterials for Tailoring Ultrasonic Transmission with Elastoacoustic Hybridization

“…Structuring their geometry enables the creation of materials with extreme quasistatic [1][2][3][4][5][6] or multifunctional properties. For example, they are shown to present zero shear modulus [7,8], high strength and low density [1,2,9], negative Poisson ratio [10], and optomechanical effects [11]. Design approaches for static properties of microlattices mostly rely on (i) varying the lattice constitutive materials [1][2][3]5] and/or (ii) selecting the unit cell geometries [6,12].…”

On the Use of Mechanical Metamaterials for Innovative Seismic Isolations Systems

“…These may include: exceptional strength-and stiffness-to-weight ratios; excellent strain recoverability; very soft and/or very stiff deformation modes; auxetic behavior; phononic bandgaps; sound control ability; negative effective mass density; negative effective stiffness; negative effective refraction index; superlens behavior; and/or localized confined waves, to name some examples (cf. [1][2][3][4][5][6][7][8][9][10][11][12][13][14] and references therein). The category of "extremal materials" has been introduced in [3] to define materials that simultaneously show very soft and very stiff deformation modes (unimode, bimode, trimode, quadramode and pentamode materials, depending on the number of soft modes).…”

“…Rapid prototyping techniques for the manufacture of materials with near-pentamode behavior have been recently presented in [8] (macroscale) and [9] (microscale). Pentamode materials have been proposed for transformation acoustics and elastomechanical cloak (refer, e.g., to the recent paper [10] and the references therein), but their potential in different engineering fields is still only partially explored.…”

“…The present study with the use of pentamode lattices as tunable seismic isolation devices, making profit from the control of the soft modes of such materials through the tuning of the bending moduli of members and junctions [8][9][10][11]. An illustrative numerical example shows a practical implementation of a pentamode lattice as a base isolation device, establishing a comparison of the elastic moduli and the force-displacement response of such a system with those exhibited by a conventional rubber bearing.…”