Metamaterials with artificially designed architectures are increasingly considered as new paradigmatic material systems with unusual physical properties. Here, we report a class of architected lattice metamaterials with mechanically tunable negative Poisson’s ratios and vibration-mitigation capability. The proposed lattice metamaterials are built by replacing regular straight beams with sinusoidally shaped ones, which are highly stretchable under uniaxial tension. Our experimental and numerical results indicate that the proposed lattices exhibit extreme Poisson’s-ratio variations between $-0.7$ and 0.5 over large tensile deformations up to 50%. This large variation of Poisson’s-ratio values is attributed to the deformation pattern switching from bending to stretching within the sinusoidally shaped beams. The interplay between the multiscale (ligament and cell) architecture and wave propagation also enables remarkable broadband vibration-mitigation capability of the lattice metamaterials, which can be dynamically tuned by an external mechanical stimulus. The material design strategy provides insights into the development of classes of architected metamaterials with potential applications including energy absorption, tunable acoustics, vibration control, responsive devices, soft robotics, and stretchable electronics.

This Letter reports a group of triply periodic co-continuous acoustic metamaterials exhibiting simultaneous wave filtering capability and enhanced mechanical properties. We numerically demonstrate the existence of complete band gaps in these acoustic metamaterials, which is attributed to the coupling effects of local resonances and Bragg scattering. Intrinsically, the coupling effects are governed by the topological arrangements of the co-continuous structures and mechanical properties of constituent phases. We further show that the frequency tunability of the complete band gaps can be achieved by tailoring the geometrical arrangements and volume fraction distribution of the co-continuous acoustic metamaterials. This work provides a clue to the design of mechanically robust acoustic metamaterials to absorb acoustic and elastic waves under harsh environments.