Simply put, metamaterials are materials that behave according to their structure, rather than their base material composition. By manipulating their internal microstructures, metamaterials can exhibit properties that would not otherwise be found in a naturally occurring material.
To date, the term has mostly been used to refer to materials which can manipulate electromagnetic waves with an unnatural refractive index. But recently, a different way of looking at metamaterials has been studied by a team at the Hasso Plattner Institute (HPI), who suggest that “so far, metamaterials were understood as materials – we want to think of them as machines.” A series of objects created by HPI that perform mechanical functions through their metamaterial configuration demonstrate this concept of “metamaterial mechanisms.”