‘Invisibility’ could be a key to better electronics

A new approach that allows objects to become ''invisible'' has now been applied to an entirely different area - letting particles ''hide'' from passing electrons, which could lead to more efficient thermoelectric devices and new kinds of electronics.

The concept - developed by MIT graduate student Bolin Liao, former post-doc Mona Zebarjadi (now an assistant professor at Rutgers University), research scientist Keivan Esfarjani, and mechanical engineering professor Gang Chen - is described in a paper in the journal Physical Review Letters.

Normally, electrons travel through a material in a way that is similar to the motion of electromagnetic waves, including light; their behaviour can be described by wave equations. That led the MIT researchers to the idea of harnessing the cloaking mechanisms developed to shield objects from view - but applying it to the movement of electrons, which is key to electronic and thermoelectric devices.

Previous work on cloaking objects from view has relied on so-called metamaterials made of artificial materials with unusual properties. The composite structures used for cloaking cause light beams to bend around an object and then meet on the other side, resuming their original path - making the object appear invisible.

''We were inspired by this idea,'' says Chen, the Carl Richard Soderberg Professor of Power Engineering at MIT, who decided to study how it might apply to electrons instead of light. But in the new electron-cloaking material developed by Chen and his colleagues, the process is slightly different.

The MIT researchers modelled nanoparticles with a core of one material and a shell of another. But in this case, rather than bending around the object, the electrons do actually pass through the particles: Their paths are bent first one way, then back again, so they return to the same trajectory they began with.