Engineers at Caltech and ETH Zürich in Switzerland have created a method to systematically design metamaterials using principles of quantum mechanics.
Their work could pave the way for wider use of metamaterials in more mainstream applications by creating a purpose-driven framework for their design.
Metamaterials are engineered materials that exploit the geometry of their internal structure to manipulate incoming waves. For example, a metamaterial that manipulates electromagnetic waves might bend light in an unusual way to create a cloaking device. Meanwhile, a wafer-thin acoustic metamaterial might reflect incoming sound waves to soundproof a room.
This ability to control waves derives from how the material is structured, often on a microscopic scale. In 2010, Caltech researchers developed an optical metamaterial that uses a surface coated with three-dimensional structures to redirect light as desired. More recently, engineers at Caltech showed that flat surfaces coated with tiny pillars of silicon could focus light like a lens.
Picture a crystal -- a solid whose physical properties are determined by the way it is built from a repeating series of atomic structures. Carbon atoms structured in flat plates create crumbly graphite, while carbon atoms structured in tetrahedra create ultra-hard diamonds. Similarly, metamaterials are constructed from a repeating series of nano- and micro-scale structures that give them their unique properties.
Despite their promise and wide array of possible applications, metamaterials will not be used widely unless engineers can design them to have particular desired properties. While much progress has been made in the design of metamaterials that interact with electromagnetic waves, overall, the design of mechanical metamaterials -- those that influence mechanical waves, such as sound waves or seismic waves -- remains a scattershot affair, says Chiara Daraio, a professor of mechanical engineering and applied physics at Caltech.
"Before our work, there was no single, systematic way to design metamaterials that control mechanical waves for different applications," she says. "Instead, people often optimized a design to fulfill a specific purpose, or tried out new designs based on something they saw in nature, and then studied what properties would arise from repeated patterns."
To read more, click here.