Underwater Invisibility Cloak Makes Objects Disappear
Posted on October 4, 2011
Using transparent sheets of carbon nanotubes researchers have built an "invisibility cloak" that works underwater. The researchers report in the journal Nanotechnology that the rapidly heated tubes create sharp heat gradients. The researchers say, "The extremely high heat transfer ability of these transparent carbon nanotube sheets enables high frequency modulation of sheet temperature over an enormous temperature range."
The mirage effect, observed in deserts or on long roads in the summer, is an optical phenomenon in which light rays are bent to produce a displaced image of distant objects or the sky. The most common example of a mirage is when a person sees 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.
In the case of the underwater invisibility cloak, the rapidly heated carbon nanotube sheets are causing light rays to bend away from the object concealed behind the device, making it appear invisible. Take a look:
Dr Ali Aliev, the lead author of the study, says, "Using these nanotube sheets, concealment can be realized over the entire optical range and rapidly turned on-and-off at will, using either electrical heating or a pulse of electromagnetic radiation. The research results also provide useful insights into the optimization of nanotube sheets as thermoacoustic projectors for loud speaker and sonar applications, where sound is produced by heating using an alternating electrical current."