In situ switchable local resonance in elastic metamaterials through bistable topological transformation

We report a topology-transformable resonator with two distinct stable states, one kinematically determinate and endowed with nearly rigid-body motion at low-frequencies, and the other accompanied by a floppy pseudo zero-energy mode capable of showing low-frequency local resonance. Through a combination of numerical simulations and experiments, we unveil the role of contact-induced topological transformation, a phenomenon that empowers the resonator with negative dynamic effective mass. We demonstrate that the bistable resonator can be embedded into elastic metamaterials to enable in situ switch of local resonance, allowing on-demand augmentation and attenuation of elastic wave propagation within a prescribed regime of frequency.