“…More recently, elastic metasurfaces have been investigated considering spatial or temporal modulations. Arrays of resonators with spatially varying resonant frequency have been used to tailor surface and edge waves to achieve wave focusing [15,16], rainbow reflection, trapping, mode conversion [17,18] and topological states along plates, half-spaces [19] or lattices [20]. Control over the effective properties of elastic metasurfaces has also been obtained through quasiperiodic arrays in space [21] or time-modulated resonators [22][23][24].…”
In this work, we investigate the dynamics of Scholte–Stoneley waves (SSWs) travelling along elastic metasurfaces, e.g. thin resonant structures embedding mechanical oscillators, placed at the interface between solid and fluid. To this purpose, an analytical dispersion law, valid in the long-wavelength regime, is derived and used to reveal the hybridization of SSWs with the collective resonance of the mechanical oscillators and the conversion of SSWs into leaky modes within the fluid. The analytical predictions are validated through numerical simulations that include both dispersive and harmonic analysis. Our findings disclose the capabilities of elastic metasurfaces in filtering, trapping and converting SSWs along fluid–solid interfaces, thus supporting the design of novel devices for solid–fluid interaction across various engineering applications, including microfluidics.
This article is part of the theme issue 'Current developments in elastic and acoustic metamaterials science (Part 1)'.
“…More recently, elastic metasurfaces have been investigated considering spatial or temporal modulations. Arrays of resonators with spatially varying resonant frequency have been used to tailor surface and edge waves to achieve wave focusing [15,16], rainbow reflection, trapping, mode conversion [17,18] and topological states along plates, half-spaces [19] or lattices [20]. Control over the effective properties of elastic metasurfaces has also been obtained through quasiperiodic arrays in space [21] or time-modulated resonators [22][23][24].…”
In this work, we investigate the dynamics of Scholte–Stoneley waves (SSWs) travelling along elastic metasurfaces, e.g. thin resonant structures embedding mechanical oscillators, placed at the interface between solid and fluid. To this purpose, an analytical dispersion law, valid in the long-wavelength regime, is derived and used to reveal the hybridization of SSWs with the collective resonance of the mechanical oscillators and the conversion of SSWs into leaky modes within the fluid. The analytical predictions are validated through numerical simulations that include both dispersive and harmonic analysis. Our findings disclose the capabilities of elastic metasurfaces in filtering, trapping and converting SSWs along fluid–solid interfaces, thus supporting the design of novel devices for solid–fluid interaction across various engineering applications, including microfluidics.
This article is part of the theme issue 'Current developments in elastic and acoustic metamaterials science (Part 1)'.
“…Emerging directions envisioned are sensing 30 , 31 , energy harvesting 32 , 33 , and actuating 34 mechanical metamaterials. Based on the dynamic features of architected, photonic metamaterials 35 , 36 , topological wave physics has also been reported as a promising direction for mechanical metamaterials in recent studies 37 – 40 . Fig.…”
Mechanical metamaterials enable the creation of structural materials with unprecedented mechanical properties. However, thus far, research on mechanical metamaterials has focused on passive mechanical metamaterials and the tunability of their mechanical properties. Deep integration of multifunctionality, sensing, electrical actuation, information processing, and advancing data-driven designs are grand challenges in the mechanical metamaterials community that could lead to truly intelligent mechanical metamaterials. In this perspective, we provide an overview of mechanical metamaterials within and beyond their classical mechanical functionalities. We discuss various aspects of data-driven approaches for inverse design and optimization of multifunctional mechanical metamaterials. Our aim is to provide new roadmaps for design and discovery of next-generation active and responsive mechanical metamaterials that can interact with the surrounding environment and adapt to various conditions while inheriting all outstanding mechanical features of classical mechanical metamaterials. Next, we deliberate the emerging mechanical metamaterials with specific functionalities to design informative and scientific intelligent devices. We highlight open challenges ahead of mechanical metamaterial systems at the component and integration levels and their transition into the domain of application beyond their mechanical capabilities.
“…[20] Initial research concerning topological metamaterials focused on the theoretical prediction and experimental demonstration of 0D topological states in 1D mechanical structures (e.g., the wave is localized at a point in a rod) and 1D topological states in 2D mechanical structures (e.g., the wave is localized along a line waveguide in a thin plate). [21][22][23][24][25][26][27][28][29][30][31][32][33] Building upon the promising initial outcomes, researchers have begun to explore beyond the traditional 1D and 2D systems to achieve 2D topological states in 3D structures (e.g., the wave is localized along a planar waveguide in a 3D cubic geometry). To construct 3D topological metamaterials, the elastic analogs of Weyl semimetals or the quantum valley Hall effect (QVHE) from electronic systems have been created by carefully configuring the spatial symmetries of 3D periodic lattice geometries.…”
Topological mechanical metamaterials unlock confined and robust elastic wave control. Recent breakthroughs have precipitated the development of 3D topological metamaterials, which facilitate extraordinary wave manipulation along 2D planar and layer‐dependent waveguides. The 3D topological metamaterials studied thus far are constrained to function in single‐frequency bandwidths that are typically in a high‐frequency regime, and a comprehensive experimental investigation remains elusive. In this paper, these research gaps are addressed and the state of the art is advanced through the synthesis and experimental realization of a 3D topological metamaterial that exploits multimodal local resonance to enable low‐frequency elastic wave control over multiple distinct frequency bands. The proposed metamaterial is geometrically configured to create multimodal local resonators whose frequency characteristics govern the emergence of four unique low‐frequency topological states. Numerical simulations uncover how these topological states can be employed to achieve polarization‐, frequency‐, and layer‐dependent wave manipulation in 3D structures. An experimental study results in the attainment of complete wave fields that illustrate 2D topological waveguides and multi‐polarized wave control in a physical testbed. The outcomes from this work provide insight that will aid future research on 3D topological mechanical metamaterials and reveal the applicability of the proposed metamaterial for wave control applications.
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