Multichannel topological elastic waveguide in a multilayer Kagome phononic crystal

By examining the geometric characteristics of various boundaries formed within the Kagome phononic lattice and vertically stacking the lattices, we designed an elastic waveguide that enables selective propagation of topologically protected edge modes across layers in a bilayer system. This layer-selective transmission is manifested as polarized boundary modes that appear in phononic dispersions of the systems incorporating the bridge, zigzag, and armchair boundaries. We numerically demonstrated that efficient elastic layer converters and splitters can be designed, thereby paving the way for the practical development of three-dimensional elastic-wave devices.