Soft 3D Metamaterial for Low-Frequency Elastic Waves

TL;DR

This paper introduces a fully soft 3D metamaterial operating around 200Hz, combining elastomer lattices with liquid metal inclusions to control low-frequency elastic waves for potential tactile and protective applications.

Contribution

It presents a novel scalable soft 3D metamaterial design with liquid metal inclusions, enabling low-frequency wave control and practical fabrication methods.

Findings

Decouples flexural and torsional modes for band gap creation

Achieves greater attenuation than silicone elastomers at half the density

Validated by high-resolution vibrometer and accelerometer measurements

Abstract

Acoustic metamaterials offer exceptional control over wave propagation, but their potential remains unfulfilled due to fabrication constraints. Conventional processes yield mostly rigid, planar structures, whereas soft-matter alternatives have so far been confined to ultrasounds. This work overcomes prior limitations with a fully soft 3D metamaterial operating around 200Hz. The design combines a 3D-printed elastomer lattice with resonant inclusions of liquid metal, injected via a network of mesofluidic channels. Its dynamic response is derived from a hybrid strategy uniting a lumped-element model with finite element analysis. Simulations reveal how the dual-phase design decouples flexural and torsional modes, opening a subwavelength band gap for low-frequency elastic waves. Empirical validation is achieved via a custom camera-based vibrometer. Its high spatiotemporal resolution and full-field capabilities enable direct capture of local modes and evanescent waves underlying the band gap. Accelerometer data corroborate these findings and demonstrate greater attenuation than common silicone elastomers at only half of the density. By combining scalable fabrication, compliance, and operations at frequencies relevant to human tactile perception, this novel metamaterial paves the way for lightweight, high-performance cushioning and handles that protect users from harmful vibration exposure.