UTD researchers have unveiled their most recent discoveries in creating one of the more sought-after science fiction devices: the invisibility cloak.
The results of five years of work, a so-called “cloaking device” has been created that effectively hides objects from view, making them seem invisible. To make it work, the device utilizes sheets of carbon nanotubes, or CNTs, attached to a power source.
In mere milliseconds, the CNTs can reach temperatures of around 2,000 degrees Celsius. The general idea is that as the air around the nanotubes heats up, the density of the air decreases, bending the light and creating a mirage effect.
The effect occurs when light is bent away from an object and creates a displaced image of another object. This is seen commonly as a shimmer on long roads during a hot day.
“Carbon nanotubes are small, tiny, and have an almost negligible heat capacity,” said Ali Aliev, lead author on the project and research scientist at the Alan G. MacDiarmid NanoTech Institute here at UTD. “I had this idea that if you can so rapidly increase temperature in air or in some medium, then you can also change, at the same rate, the refractive index. You can, by this way, refract light.”
Currently, the device does not achieve true invisibility. Rather, the cloak hides behind the displaced image of surrounding objects, making the cloak only seem invisible. Aliev said that true invisibility involves bending light around an object, not just bending light away from it. This would eliminate the shadow that the cloak leaves behind, and would appear as though light was traveling straight through the device.
Very little power is required to activate the cloaking device, making it extremely efficient. In previous tests, the cloak used just six watts of power. However, the system is also very fragile. Due to the nature of CNTs, virtually any contact with them will break the delicate chain of carbon molecules. One of the challenges now is to increase the durability of the cloaking device.
While Aliev preformed the experiments for the project, other researchers played a big role in the development of the cloak. Professor Yuri Gartstein performed the supporting calculations, while Ray Baughman, director of the Alan G. MacDiarmid NanoTech Institute, contributed to analyzing the results of the project.
The discovery in the field of invisibility was nearly accidental. While working on a separate project for sound generation using CNTs, Aliev noticed a slight shimmer around the nanotubes he was applying a current to. He later applied this observation to a study involving negative refraction, bringing Aliev and the other researchers to where they stand today.
Aliev said the technology has applications other than making objects invisible. He is currently working on various other CNT projects, such as a speaker made of the nanotubes, and a new type of camera lens. Both projects contain no moving parts and represent cheaper, more efficient alternatives to relatively old technology.
