Hidden in plain sight

The idea of being able to become invisible, especially by simply covering up a person or an object with a special cloak, has a perennial appeal in science-fiction and fantasy literature. In recent years, researchers have found ways to make very exotic “metamaterials” that can perform a very crude version of this trick, keeping an object from being detected by a certain specific frequency of radiation, such as microwaves, and only working at microscopic scales. But a system that works in ordinary visible light and for objects big enough to be seen with the naked eye has remained elusive.

Now, a team of researchers in the Singapore-MIT Alliance for Research and Technology (SMART) Centre has found a relatively simple, inexpensive system that can hide an object as big as a peppercorn from view in ordinary visible light. The team’s discovery has been published online in Physical Review Letters and will appear soon in the print version of the journal.

Unlike the other attempts to produce invisibility by constructing synthetic layered materials, the new method uses an ordinary, common mineral called calcite — a crystalline form of calcium carbonate, the main ingredient in seashells. “Very often, the obvious solution is just sitting there,” says MIT mechanical-engineering professor George Barbastathis, one of the new report’s co-authors.