Explaining Metamaterials

We live in a world of waves. The radio waves hitting your car’s antenna and the light coming in through its windshield, the X-rays that can detect a tumor and the gamma radiation that can destroy it are all different facets of the same phenomenon: electromagnetism. As one of the fundamental forces of nature, its imprint can be felt on almost everything in the universe.

The difference between these waves that permeate the everyday aspects of our lives is where they fall on the electromagnetic spectrum, or how long it takes for each of these waves to crest, fall, and repeat. The waves carrying a radio broadcast might be a meter long, for example—long enough to swerve around obstacles on their way to your receiver. The light waves that are coming from the screen and into your eyes are a million times smaller than that, and radioactive gamma waves are a million times smaller still.

Mastering the movement of these waves is at the heart of much of modern technology, and at Penn, no one does that quite like Nader Engheta.

The H. Nedwill Ramsey Professor of Electrical and Systems Engineering at the School of Engineering and Applied Sciences, Engheta is a leading figure in the nascent field of metamaterials. Combining several branches of physics and engineering with a healthy dose of nanotechnology, metamaterials can bend and manipulate waves like nothing in nature can.

Objects made from natural materials have atoms and molecules that are arranged in certain patterns dictated by the laws of physics and chemistry; those patterns give natural materials their electromagnetic properties, which in turn determine how they influence the properties of waves.

With researchers’ increasing abilities to engineer materials on ever-smaller scales, they can take these principles and apply them in more complex ways. Engheta and his colleagues start with the patterns of naturally occurring materials, but organize those patterns into larger ones. The atomic patterns found in a nanoscale cube of gold might be incorporated into an array of many cubes of gold, precisely spaced within a block of glass. This composite material would have properties that couldn’t be achieved in either gold or glass alone.

By designing arrangements of shapes with features that are smaller than a given wavelength, Engheta and other metamaterials researchers are developing “super lenses,” which have unprecedented magnification abilities, and “cloaking devices,” which can bend waves around an object, rendering it effectively invisible.

Engheta is also working on structures consisting of metamaterials arranged in even larger patterns—effectively, meta-metamaterials.

Text by Evan Lerner
Video by Kurtis Sensenig