Nonlocal Metaspire: A Scalable Elastic Material Platform With Decoupled Mechanical Modes.

Nonlocal metamaterials, which are metamaterials that interact with non-neighboring unit cells, have recently attracted growing attention as a new paradigm for wave control owing to their extraordinary band structures. However, existing nonlocal metamaterials remain limited in scalability, making it difficult to implement multiple nonlocal couplings and higher-dimensional arrays. Elastic nonlocal metamaterials have an additional limitation of mode coupling, which hinders clear investigations of unique nonlocal wave phenomena in individual elastic wave modes. This study addresses these limitations by proposing a new material platform for elastic nonlocal metamaterials, leveraging the "Metaspire" architecture with sequential rotation. Subsequently, the detailed wave motions around the maxon and roton are investigated, and the role of nonsymmorphic symmetry in flexural band behavior is further examined. In addition, actual fabrication and experimental validation are conducted to further support the proposed approach. The results quantitatively demonstrate the high scalability of the proposed method and its suppression of mode coupling. The proposed material platform provides a basis for the development of multifunctional wave platforms, thereby enabling various new-wave systems and devices.