Programmable Rainbow Trapping and Band-Gap Enhancement via Spatial Group-Velocity Tailoring in Elastic Metamaterials

Stretch here, not there: Programmable tailoring of a wave's group velocity in space, achieved via synthetic impedance circuitry with digital signal processing, enables substantial design flexibility for devices. Here researchers demonstrate the programming of ``rainbow trapping'' (slowing waves to a temporary stop, based on frequency) in an elastic waveguide for chosen spatial grading profiles. The use of spatially graded resonators also significantly enhances the band gap's bandwidth, beyond that for a uniform resonator. This class of metamaterials enables simple on-demand programming of elastic wave trapping, spatial filtering, and attenuation through a digital interface.