‘Digital’ Metamaterials Constructed from the Bit Up

There could be a simpler way to create metamaterials, ultimately leading to light-bending invisibility cloaks and other seemingly impossible devices.

A team from the University of Pennsylvania has discovered that a metamaterial with a given permittivity can be designed out of any two materials, as long as the permittivity of one is positive and the other is negative. Called digital metamaterials, they are composed of metamaterial “bits” that are combined into “bytes,” similar to digital information.

A lens made out of identical metamaterial bytes (top) can be made flat by altering the composition of the bytes (bottom). Courtesy of the University of Pennsylvania.

The researchers found that by carefully arranging bytes into complex patterns, they could produce flat lenses. Their work has also demonstrated the feasibility of digital metamaterial hyperlenses, which can image objects smaller than the wavelength of light, as well as waveguides that channel light around curves and corners, creating the illusion of invisibility.

The metamaterial bytes can take different shapes, such as nanoscale cylinders. In the study, the researchers altered the radii of a nanoscale cylinder’s core and shell and determined which of the two bits were on the inside or outside — this allowed them to demonstrate mathematically that a bulk metamaterial of nearly any permittivity can be achieved.

“With binary systems, we can take an analog signal — a wave — and sample it, discretize it and ultimately express it as a sequence of 0s and 1s,” said professor Dr. Nader Engheta. “We’re applying the same process to materials, looking at the permittivity it would need to have in each point in space in order for it to perform the function we want.”

The work was funded by the U.S. Office of Naval Research’s Multidisciplinary University Research Initiative. The research was published in Nature Materials (doi: 10.1038/nmat4082).

For more information, visit www.upenn.edu.