How to Build a Better Invisibility Cloak
Researchers have a design for a cloak that makes objects appear flat
Cloaking devices — or “metamaterials” that scatter light — have been in university labs for years. But electrical engineers at U.C. San Diego claim they’ve solved a few key problems that make existing cloaks too obvious to the human eye.
First, let’s back up a moment. For the most part, metamaterials in cloaking devices are really thick and bulky. Far too bulky to be practical. The second problem is that the cloaks scatter light at lower intensities than when the light first touches the cloak — and all that low-intensity light is still within visual frequencies.
This means we perceive the area around those cloaks to be darker than its surroundings. It’s a dead giveaway.
But the U.C. San Diego engineers claim they’ve corrected those two issues in a recent paper. A very thin sheet of Teflon peppered with tiny dielectric cylinders can scatter light while being “almost lossless,” they claim, meaning there’s little to no difference in the intensity of light around the cloak.
Their conclusions derive from some complicated math — and you can read the paper here. But if it works, “any observer will just see a flat ground plane and the scatterer will be invisible and thus effectively cloaked.” Plus the cloak is less than an inch thick.
A press release from U.C. San Diego described it in more detail.
In their experiments, the researchers specifically designed a “carpet” cloak, which works by cloaking an object sitting on top of a flat surface. The cloak makes the whole system — object and surface — appear flat by mimicking the reflection of light off the flat surface. Any object reflects light differently from a flat surface, but when the object is covered by the cloak, light from different points is reflected out of sync, effectively cancelling the overall distortion of light caused by the object’s shape.
That three-dimensional object now looks flat, imperceptible and without a shadow. It’s not perfectly invisible, but it might be enough to fool a human eye that isn’t looking closely.
The Pentagon’s official science blog picked up on the research. The U.S. military has long sought far-out stealth cloaks to hide soldiers and vehicles. It’s unclear if the engineers’ design can work on a larger scale — the design uses a cloak over a wedding ring as an example — but the blog suggested that thin cloaking material could one day cover drones … maybe.
In theory, creating a cloaking device would be used to conceal larger objects. This cloaking device would be valuable to many technologies, including unmanned air vehicles (UAVs) due to the capability to disappear from view and leaving no visual, electronic or infrared signature for an enemy to detect. Creating the effect of an invisibility cloak offers a real-world solution to concealment, which can provide the military with air superiority. While this cloak has numerous applications for the military, this technology will create a ripple effect beyond the battlefield that will improve the performance of other diverse applications.