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Metamaterials for wave control
Metamaterials are architected solids featuring exotic properties that typically surpass those exhibited by conventional materials available in nature. Metamaterials consist of a network of structural elements which, taken individually, are characterized by relatively simple geometries. However, because of their internal architecture, metamaterials globally display vastly more complex behavior than their individual components. Acoustic metamaterials are especially interesting for vibration and sound control applications due to their unique wave manipulation capabilities. For example, acoustic metamaterials can be designed to operate as mechanical filters and attenuate excitations with frequencies falling in bands known as bandgaps. Other designs allow focusing the energy of waves along frequency- dependent directions, thus acting as directional actuators and sensors. Recent applications include materials with unconventional refractive indices, acoustic cloaks and hyper-lenses. A variety of these effects have been demonstrated with remarkable clarity by CEGE researchers using an experimental platform involving Lego® bricks. [39]