Stealth Technology: From Spy Flies to Invisibility Cloaks

To maintain an ultra-low profile, the military and other government agencies rely on stealth technologies. Unmanned drones can cross into enemy territory undetected, for instance, and spies can whip out subminiature cameras to sneakily snap photos. But the future of stealth tech hinges on even smaller gadgets and gizmos to complete high-risk missions. Scientists and engineers are discovering mind-boggling methods for developing not only incredibly tiny stealth tools but also a way to make stuff disappear completely.

I Spy a Robotic Fly

The U.S. military uses specially designed planes that evade radar detection, and it may soon have an even more undetectable piece of equipment to add to its stealth arsenal. The Defense Advanced Research Projects Agency (DARPA), the U.S. Department of Defense and intelligence agencies have invested a decent amount of dollars in robotic flying insects. These mechanical bugs could buzz around capturing camera footage, detecting hidden weapons and electronically tagging sites of interest without being noticed.

In 2008, a team of Harvard engineers unveiled the first two-winged robotic insect that was able to take flight in the same way as the real thing. Accomplishing that take-off was no small feat since insects don't fly like airplanes. While fixed-wing airplanes stay afloat due to steady state aerodynamics, flies have mobile wings that stir up circular air currents all around them. The Harvard robo-fly was attached to a guide wire and couldn't hover solo, but the breakthrough bodes well for these winged drones.

If the robo-fly ever gets off the ground, engineers at the California Institute of Technology patented a power-friendly microchip digital camera in 2009 that could work as its eyes. Before then, the imaging sensors and recording circuitry had to be divided among two separate chips, which required extra electricity, weighing down a robo-bug.

Now You See Me, Now You Don't

Robotic flies are pretty nifty, but what can be stealthier than an invisibility cloak? Around 2002, researchers at the University of Tokyo devised a system for reflecting background scenery onto a person or object and rendering it essentially indiscernible. Referred to as optical camouflage, that cloaking process probably wouldn't work for real-world reconnaissance. The unwieldy system involved a specialized reflective material (the "cloak"), a camera to capture the background images, a computer that fed those images to a projector and a device that directed light and the background images from the projector onto the cloak.

However, a team at Duke University has developed a more feasible invisibility cloak that doesn't require the extra equipment. In 2009, the engineers built a 20-inch (50-centimeter) by 4-inch (10-centimeter) cloth from a kind of meta-material, which is an artificial composite material designed on the molecular level to manipulate its interactions with electromagnetic waves. The material particles are even smaller than visible light waves, which allows the rays to essentially flow around them and remain undetectable to the eye. In other words, the cloak channels light and electromagnetic waves around objects, rather than reflecting off of them.

Made from microscopic bits of fiberglass and copper, the cloth cost little to make, although it's only capable of cloaking in two dimensions. Nevertheless, the Duke engineers couldn't hide their excitement about the not-so-stealthy breakthrough.