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New coating by 'U' researchers makes 3-D objects look invisible

By Claire Goscicki, Daily Staff Reporter
Published November 29, 2011

The famous invisibility cloak of the Harry Potter series may one day be a reality thanks to a new object-coating technique developed by University researchers.

The coating — a thin layer of carbon nanotube about half the thickness of a sheet of paper — can be applied to objects to render their three-dimensional properties invisible. Jay Guo, a University professor of electrical engineering and computer science, was the primary investigator on the study, which was recently published in the scientific journal Applied Physics Letters.

Guo explained that the coating conceals objects in a way that makes them appear as black, flat sheets.

“The carbon nanotube layer is a perfect absorber; it absorbs all light,” he said. "All of the detailed structures of the object become invisible.”

While the ability of the carbon nanotube material to absorb light is well-known throughout the scientific community, Guo and his research team — including Haofei Shi, a University research fellow of electrical engineering and computer science, and Rackham students Hyoung Won Baac and Jong Ok — discovered the most efficient way to space the tubes to achieve the highest degree of invisibility. The coating’s success depends on the limitations of the human eye, Guo said.

“Looking at an object, the reason you can perceive it is because of light, (which) is either reflected or scattered from the object,” he said. “If there’s no light coming into your eyes, then things become unperceivable.”

However, unlike the magical cloaks used by fictional wizards, Guo said the coating can’t completely hide an object because it can’t conceal the object’s shadow. A coated object must be placed against a dark background to become completely invisible.

The carbon nanotube could potentially be used by the military for national security purposes, like concealing an airplane against the night sky, according to Guo.

Guo’s curiosity about objects and their visibility extends to the study of space. He said he is particularly intrigued by the properties of dark matter — invisible space matter that accounts for much of the universe’s mass and may have similar properties to the carbon nanotubes.

Guo hypothesizes that the coating could potentially cover extremely large objects like planets.

“It’s certainly possible to hide an object of that size,” he said.


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