Invisibility cloaks have been everywhere lately and I’ve been getting a little blasé about them but then I saw this Oct. 4, 2011 news item on physorg.com,

Scientists have created a working cloaking device that not only takes advantage of one of nature’s most bizarre phenomenon, but also boasts unique features; it has an ‘on and off’ switch and is best used underwater.

For the first time, I was able to see an invisibility cloak in action, here’s the video,

For the curious here’s how it works (from the Oct. 4, 2011 news release on the Institute of Physics website),

This novel design, presented today, Tuesday 4 September [Tuesday 4 October?], in IOP [Institute of Physics] Publishing’s journal Nanotechnology, makes use of sheets of carbon nanotubes (CNT) – one-molecule-thick sheets of carbon wrapped up into cylindrical tubes.

CNTs have such unique properties, such as having the density of air but the strength of steel, that they have been extensively studied and put forward for numerous applications; however it is their exceptional ability to conduct heat and transfer it to surrounding areas that makes them an ideal material to exploit the so-called “mirage effect”.

…

The most common example of a mirage is when an observer appears to see pools of water on the ground. This occurs because the air near the ground is a lot warmer than the air higher up, causing lights rays to bend upward towards the viewer’s eye rather than bounce off the surface.

This results in an image of the sky appearing on the ground which the viewer perceives as water actually reflecting the sky; the brain sees this as a more likely occurrence.

Through electrical stimulation, the transparent sheet of highly aligned CNTs can be easily heated to high temperatures. They then have the ability to transfer that heat to its surrounding areas, causing a steep temperature gradient. Just like a mirage, this steep temperature gradient causes the light rays to bend away from the object concealed behind the device, making it appear invisible.

With this method, it is more practical to demonstrate cloaking underwater as all of the apparatus can be contained in a petri dish. It is the ease with which the CNTs can be heated that gives the device its unique ‘on and off’ feature.

Congratulations to Dr. Ali Aliev (lead author) and the rest of the University of Texas at Dallas team!

ETA Oct. 5, 2011: I added the preposition ‘of’ to the title and I’m adding a comment about invisibility cloaks.

Comment: Most of the invisibility cloaks I’ve read about are at the nanoscale which means none of us outside a laboratory could possibly observe the cloak in action. Seeing this video demonstrating an invisibility cloak in the range of visible light and at a macroscale was a dream come true, so to speak.