Make yourself invisible

Researchers take one step closer to a perfect invisibility cloak

BY NICOLETTE EMMINO

Invisibility is an intriguing futuristic possibility. Growing interest in such mystery of making yourself invisible began as far back as 1933 with the science-fiction film “The Invisible Man” and ranges all the way up to present-day Harry Potter films in which students possess invisibility cloaks.

Six years ago, a team of electrical engineers from Duke University created the first functional cloaking device. This cloak worked by deflecting microwave beams so that they would flow around an object. Although this device seemed effective and was a step in the right direction, Nathan Landy, a graduate student from the team, developed a new design that improves upon the original cloak.

Landy and his new invisibility cloak. (Image via Duke University Photography.)

The original invisibility cloak was flawed due to the appearance of minor reflections around the edges of the device. Landy has now designed a new way of controlling or transmitting light and other waves that eliminate the appearance of reflections (similar to those you see in glass).

The old and new invisibility cloaks are composed of “meta-materials,” manmade objects that have properties that natural objects don’t have and can interact with electromagnetic waves in ways that natural objects can’t.

The original cloak comprised parallel and intersecting strips of fiberglass and copper rings (similar to those used in computer circuit boards). The new and improved cloak uses added strips of copper to create a better-performing material. The two-foot-square strips form a diamond shape, leaving the center empty.

“Each quadrant of the cloak tended to have voids, or blind spots, at their intersections and corners with each other. After many calculations, we thought we could correct this situation by shifting each strip so that it met its mirror image at each interface,” said Landy.

Landy’s new cloak does its job almost perfectly, splitting light into two waves so that it travels around the object. The two waves then re-emerge as one unified wave, creating little reflection and rendering the object invisible.

Future application

Landy and the team suggest that the new approach could have further applications than just invisibility cloaks. It could benefit the fiber-optics field by making metamaterials seem straighter by smoothing out twists and turns, and can also come to benefit wireless communications and radar applications.

The team is now working to cloak 3D objects, which will prove more challenging than the 2D objects they’ve been working with, but will also bring us one step closer to real invisibility cloaks allowing us to roam around without being seen.

Other ways to make things invisible

Invisibility cloaks aren’t the only way to make things disappear. In the beginning of the year, Pentagon scientists made an actual event disappear for 40 picoseconds. Usually, light appears in a constant flow, but by manipulating the ongoing flow, an event could occur without anyone being able to observe it. The experiment was conducted by passing a beam of green light through a cable, splitting it into two frequencies (slower and faster frequencies). Then the team shot a red laser through the beams. This shot occurred in a time gap making it unperceivable to the naked eye for a tiny moment.

The “mirage effect,” created by researchers from the University of Texas, has also been proven to make object invisible. The photothermal deflection process uses a carbon nanotube aerogel sheet as a heat source. Electric current is passed through the carbon nanotubes, which create very high temperatures, causing light to bounce off, and as a result hide any objects behind it.

A company called BEA Systems tested an infrared invisibility cloak last year. The camouflage technology used hexagonal pixels that could change their temperature quickly enabling even moving vehicles to become unseen with heat-sensitive cameras. ■