Scientists step closer to creating invisibility cloaks

In a first, scientists have made an object disappear by using a composite material that can enhance an object's surface properties, an advance that may lead to practical invisibility cloaks.
Researchers from at Queen Mary University of London (QMUL) School of Electronic Engineering and Computer Science, showed for the first time a practical cloaking device that allows curved surfaces to appear flat to electromagnetic waves.
"The design is based upon transformation optics, a concept behind the idea of the invisibility cloak," said Yang Hao from QMUL.
"Previous research has shown this technique working at one frequency. However, we can demonstrate that it works at a greater range of frequencies making it more useful for other engineering applications, such as nano-antennas and the aerospace industry," Hao said.

The researchers coated a curved surface with a nanocomposite medium, which has seven distinct layers (called graded index nanocomposite) where the electric property of each layer varies depending on the position.
The effect is to 'cloak' the object: such a structure can hide an object that would ordinarily have caused the wave to be scattered.

The underlying design approach has much wider applications, ranging from microwave to optics for the control of any kind of electromagnetic surface waves.
"The study and manipulation of surface waves is the key to develop technological and industrial solutions in the design of real-life platforms, for different application fields," said Luigi La Spada from QMUL.

"We demonstrated a practical possibility to use nanocomposites to control surface wave propagation through advanced additive manufacturing," said La Spada.
"Perhaps most importantly, the approach used can be applied to other physical phenomena that are described by wave equations, such as acoustics," he added.
The study was published in the journal Scientific Reports.