Reprogrammable Phononic Metasurfaces

Phononic metamaterials rely on the presence of resonances in a structured medium to control the propagation of elastic waves. Their response depends on the geometry of their fundamental building blocks. A major challenge in metamaterials design is the realization of basic building blocks that can be tuned dynamically. Here, a metamaterial plate is realized that can be dynamically tuned by harnessing geometric and magnetic nonlinearities in the individual unit cells. The proposed tuning mechanism allows a stiffness variability of the individual unit cells and can control the amplitude of transmitted excitation through the plate over three orders of magnitude. The concepts can be extended to metamaterials at different scales, and they can be applied in a broad range of engineering applications, from seismic shielding at low frequency to ultrasonic cloaking at higher frequency ranges.

"On-the-fly" steering of mechanical waves in time and space is realized. By harnessing geometric and magnetic nonlinearities, 3D-printed phononic metamaterials change their shape from 2D to 3D. This shape change shifts its dynamical characteristics from attenuating waves to permitting their propagation. Such change is dynamic, element-wise, noninvasive, and reversible; therefore it is referred to as reprogramming of matter.

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