Researchers with the University of Texas at Dallas have developed an “invisibility cloak” composed of carbon fibers which is capable of producing the illusion that objects behind it have vanished. The device was created but UT Dallas research scientist Dr. Ali Aliev.
The “cloak” is composed of sheets of carbon nanotubes, microscopic hollow tubes made of carbon atoms arranged in a single-atom-thick layer. The tubes are conductive, and when an electrical current runs through the sheet of tubes, the effect is produced.
The effect, which works best underwater, is achieved by making use of the same physics that causes mirages on hot, sunny days. Light is bent when it crosses sharp boundaries between media of different densities. This can be seen, for instance, when an object in water appears to be bent. Mirages occur when the ground is heated and causes the air just above it to become heated as well. As distant light moves between the cool air and the layer of hotter air just above the ground, it is bent, causing observers farther along to see not the light coming from the ground itself, but rather more distant light from the sky that has been bent upwards.
Previous invisibility cloaks were laboratory prototypes that commonly cloaked paperclips, thimbles, plastic cylinders, or small objects, and held no hope as practical devices. Many cloak claims place the object in shadow, or render them black, so they block the view to the other side.
The cloak composed of carbon nanotubes works in a similar way. As electrical current runs through the cloak, they heat up, and a heated layer of air (or water, as the case may be) is created. Light rays approaching at an angle are bent by this heated layer, causing viewers to see an image not of the cloak, but of bent rays from the surroundings. The sheet is replaced, to the eye, by a what appears to be a shimmery pool, as in a mirage.
In the paper, written by Dr. Aliev and co-authors Yuri Gartstein and Ray Baughman, both also of the University of Texas at Dallas, the researchers note, “the remarkable performance of nanotube sheets suggests possible applications as photo-deflectors and for switchable invisibility cloaks, and provides useful insights into their use as thermoacoustic projectors and sonar.” According to Wired.com, a spokesperson for the Institute of Physics praised the research, saying, “It is remarkable to see this cloaking device demonstrated in real life and on a workable scale. The array of applications that could arise from this device, besides cloaking, is a testament to the excellent work of the authors.”
The research was supported by the Office of Naval Research, NASA, the Air Force Office of Scientific Research, and the Robert A Welch Foundation.