Tunablility at the ultra-low-frequency via inerter-based elastic metamaterials

Inerter is a mechanical device capable of exhibiting an inertial effect that is orders-of-magnitude larger than its physical mass. By coupling linear motion with rotational motion of a built-in flywheel, the inerter generates a response force proportional to the relative acceleration between its two independent terminals. Here, we experimentally fabricate and characterize vibro-elastic metamaterial designs with embedded interters. Aided by computational simulations, our design aims to demonstrate a unique and fundamental advantage in forming a bandgap at extremely low frequencies. After fabrication, we perform wave-propagation testing on samples with both longitudinal (pressure) and transverse (shear) waves. The results show that our design can be made tunable by changing either the effective rotational inertia or the effective connection stiffness. This significantly enhances the metamaterial’s applicability in mitigating real-world structural vibration with at ultra-low frequency and very long wavelength. Our data indicate that inerter-based design may outperform traditional locally resonant metamaterials and could be more suitable for broader application scenarios, such as seismic events.