Mode hybridization in DNA-inspired helical metamaterials with variable centro-asymmetry

Abstract

We study helical acoustic metamaterials and demonstrate the ability to vary the materials' dispersion properties by controlling geometrical structure and mass distribution. By locally adding eccentric, higher density elements in the unit cells, we perturb the moment of inertia of the system and introduce centro-asymmetry. This allows controlling the degree of mode coupling and the width of subwavelength bandgaps in the dispersion relation, which are the product of enhanced local resonance hybridization. We characterize the distinct normal modes in our metamaterials using finite element simulations and analytically quantify the coupling between each mode. The evolution of acoustic bandgaps induced by the increasing level of centro-asymmetry is experimentally validated with 3D-printed structures.