New approach for invisibility

A team at MIT has developed a new approach for allowing objects to become “invisible.” The new concept lets particles “hide” from passing electrons, which could lead to more efficient thermoelectric devices in the future.

Electrons normally travel through material in a similar way to the motion of electromagnetic waves and their behaviour can be described by wave equations. This gave the researchers the idea of harnessing existing cloaking mechanisms developed to shield objects from view, but applying it to the movement of electrons.

Previous work on cloaking has relied on composite structures that cause light beams to bend around an object and then converge on the other side, making the object appear invisible. The researchers modelled nanoparticles with a core of one material and the shell of another. Rather than bending around the object, the electrons actually pass through the particles: their paths are bent first one way, then back again, so they return to the same trajectory as the start.

The concept works in computer simulations, but now the team will try to build real devices to see whether they perform as expected.

“This was a first step, a theoretical proposal. We want to carry on further on how to make some real devices out of this strategy,” explained Bolin Liao, who developed the concept which is described in Physical Review Letters.

The researchers want to see if the results can be replicated with other materials such as a two-dimensional sheets of graphene, which might offer interesting additional properties. The concept could lead to development of a new kind of switches for electronic devices. The switch might operate by toggling between transparent and opaque to electrons. Thus turning a flow of them on and off.

Xiang Zhang, professor of mechanical engineering at the University of California at Berkley said: “This is very exciting work. The group have uncovered a very interesting approach that may be very useful to thermoelectric applications.”