A new invisibility cloak mimics a mirage to make objects invisible. A video posted by the Institute of Physics (IOP) shows the device in action, making a sheet of carbon nanotubes disappear and reappear at the flip of a switch. The device was built by researchers from the University of Texas at Dallas.
Mirages are typically seen in deserts and long roads on hot days. They can make a weary traveller think pools of water are on the horizon, and the work because air near the ground is warmer than the air up a bit higher, which causes “lights rays to bend upward towards the viewer’s eye rather than bounce off the surface,” according to the IOP.
“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,” it states.
The cloak works by the same principle. The electronic sheet is heated to high temperatures, and the heat is then transferred to its surrounding areas which gives it a “steep temperature gradient,” states the IOP. The steep temperature gradient is what causes the illusion.
I would be curious to see how the invisibility cloak works outside of water, and from a different angle. There are similar cloaks out there that use these two factors to render objects invisible. The IOP compares the water to a petri dish that helps better display the effect.
I interviewed a team of researchers from the Singapore-MIT Alliance for Research and Technology (SMART) Centre, who made a working device back in February. The device used a calcite crystal and optical anisotropy that gave the illusion of invisibility. Theirs only worked on a 2D plane, however. If you tried looking at it from any different angle the illusion was gone. They mentioned it worked best underwater, just like the latest mirage one works best underwater—interesting phenomena.
There are invisibility cloaks out there that can hide objects from all angles, but they only work on a microscopic level. From what I was told, the cloak from the team at SMART was the first to work without needing a microscope to see it.