Programmable metamaterials: A rich platform for controlling a plethora of wave phenomena

Mechanical metamaterials are materials with tailored, architected geometry, designed to retain properties that do not exist or rare in nature. Most of these mechanical properties are inscribed in the material’s frequency dispersion spectrum, ranging from its stiffness at zero frequency to its wave attenuation capacity at finite frequencies. This class of materials usually features a structural pattern that repeats spatially (i.e., unit cell). A major challenge in metamaterials design is to engineer unit cells that have the ability to change their mechanical properties in a predetermined manner, within practical time frames. As a demonstration of principle, we harness geometric and magnetic nonlinearities to tune the metamaterials’ dispersion characteristics. We program our nonlinear metamaterial to redirect waves, in real-time, in an element-wise fashion. Moreover, we use it to realize the unique acoustic devices to guide and cascade waves.