Towards design of a nonlocal metasurface with highly broadening bandwidth for omnidirectional vibration isolation

As an advanced and potent emerging component for the manipulation of elastic waves, the design of passive elastic metasurfaces is predominantly constrained by narrow bandwidth limitations, posing formidable challenges for practical engineering applications. Recently, nonlocal metasurfaces have gained prominence in acoustics and optics, leveraging long-range coupling effects to induce nontrivial wave manipulation phenomena. However, research on elastic wave manipulation has predominantly concentrated on decoupled local metasurfaces, neglecting the coupling interactions between unit cells, which restricts the demonstration of broadband characteristics. It is imperative to comprehensively consider the long-range forces between unit cells to achieve robust, integrally formed, and structurally simple broadband elastic wave manipulation. This paper proposes an analytical lattice model and a broadband vibration isolation elastic metasurface design paradigm predicated on nonlocal mechanisms. The proposed nonlocal metasurface achieves omnidirectional broadband vibration isolation through phase modulation and impedance modulation by establishing meticulously designed connections between unit cells, utilizing the multi-objective evolutionary optimization algorithm (NSGA-III). A multi-degree of freedom equivalent model containing the coupled structures is developed to theoretically elucidate the impact of nonlocal physical effects on the dynamic response of the metasurface. An irregularly shaped vibration-isolation cage was designed, and its omnidirectional broadband elastic wave isolation capability was validated through numerical simulations and experiments. This strategy provides a reliable and effective approach to extending the operational bandwidth of existing local metasurfaces, thereby facilitating broadband elastic wave manipulation metasurface for diverse application scenarios.