Synthesis of a Fully Mechanical Stiffness-Tunable Chiral Waveguide for Controlled Bloch Wave Propagation
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The mitigation and control of vibrations in elastic media is a fundamental problem in modern mechanics and materials engineering. In recent years, metamaterials [1] have emerged as powerful tools for wave manipulation, enabling frequency filtering, directional wave guiding, and energy harvesting through carefully-designed microstructural architectures or by incorporating electro- or magneto-responsive constituents. Here, we discuss the response of a recently-proposed mechanically-tunable meta-filter [2] based on a chiral waveguide architecture composed of mass-spring elements with fully adjustable stiffness. The tunability is achieved through an entirely mechanical system that enables accurate and reversible control of Bloch wave propagation characteristics. Specifically, each spring consists of an elastic ring connected to neighboring masses via appendages made of flexural-tensegrity segmental beams [3], whose effective bending stiffness can be continuously modulated by varying the pre-tension in an internal cable. This configuration allows for systematic tailoring of the Floquet–Bloch band structure, resulting in adaptive wave-filtering capabilities without reliance on thermo-active or electro-active materials. The proposed concept offers a lightweight, reconfigurable, and scalable solution that can be naturally extended to higher-dimensional lattice-based metamaterials. Moreover, the associated design framework supports comprehensive parametric analyses, providing a robust basis for the rational design and prototyping of advanced mechanical meta-filters for practical vibration control applications. [1] Dalela S., Balaji P. S., Jena D. P., A review on application of mechanical metamaterials for vibration control, Mechanics of advanced materials and structures, 29(22), 3237-3262, 2022. [2] Boni C., Bacigalupo A., Design of a chiral waveguide with mechanically-tunable stiffness for Bloch wave propagation control, International Journal of Mechanical Sciences, 111051, 2025. [3] Boni C., Silvestri M., Royer-Carfagni G., Flexural tensegrity of segmental beams, Proceedings of the Royal Society A, 476(2237), 20200062, 2020.
