Tailoring of interface modes in topologically protected edge states with hourglass lattice metamaterials

Nonreciprocity and topologically protected wave propagation have significant implications on how energy and information are transmitted or guided within materials to control or mitigate its effects. The major challenge in tailoring interface mode arises from challenges related to the customizability and linearity of interface lattice, moreover, there is a scarce of experimental analysis reported in the literature. Our study has focused on obtaining topologically protected nontrivial interface modes at a specific frequency by breaking the inversion symmetry through novel hourglass metastructure both theoretically and experimentally. Detailed work on wave transmission, dispersion, and bandgap analysis are carried out considering topological metamaterials. New cellular configurations based on regular honeycomb and auxetic cells, and variations of their geometric parameters responsible for interface mode tuning are reported here. A generalized theoretical scheme for different combinations of the hourglass lattice is derived at the interface, and consequent energy harvesting and damping prospects are reported. Analytical modeling of topological metamaterial lattice along with numerical simulation, additive layer manufacturing (3D printing), and finally experimental validations are carried out to justify the behavior and reveal the underlying physics responsible for its unique behavior. Three types of configurations including hourglass lattice at the interface define a general framework for introducing lattice-based imperfections in the continuous elastic structure for potential engineering applications. The localized topological interface mode obtained within the bandgap can be tuned significantly with the help of latticed hourglass and may be utilized for the purpose of wave guiding, wave focusing, and energy harvesting within the isolation zone.