13-06-2025
Master of disguise: Meet the inventor of a state-of-the-art invisibility cloak
In some ways, he is himself the stuff of science-fiction.
For thousands of years, dating to ancient Greek and Welsh myths, then sci-fi and the worlds of HG Wells and Harry Potter, storytellers and scientists have toyed with the idea of the invisibility cloak.
Wells, who foresaw the aircraft and army tank, atomic bomb and Wikipedia, wrote of a scientist committed to invisibility in The Invisible Man (1897). This scientist learnt how to change the way light reflected off his body.
In Canada, George Eleftheriades has done something similar. He can't erase himself from view, but he has so far been able to hide large, bulky objects from radar, using just a thin layer of rather magical antennae.
It's a bit like noise-cancelling headphones, he says, with remarkable modesty. (It isn't that simple at all.) But before we get to how it works, a bit about who he is.
Eleftheriades, 60, is a professor of electrical and computer engineering at the University of Toronto. Growing up in Cyprus, he was obsessed with science as a child. He had chemicals bubbling over in his room, microorganisms squirming under microscopes, and burn marks on the wooden floor, he says, with a laugh.
He was fascinated by radiowaves, which felt a bit like magic. As he grew, he had his imagination sparked by the way ancient Greek philosophers, particularly Heraclitus, viewed scientific concepts. (Heraclitus, of course, famously expressed the idea of constant flux by noting that one can't step into the same river twice.)
Following where his heart led, Eleftheriades studied electrical engineering in Athens, after which he moved to the US for a Master's and PhD from University of Michigan. He worked on ultra-sensitive radiowave receivers in Switzerland from 1994 to '97, and has been at University of Toronto ever since.
A decade ago, he became something of a 'stealth' agent. In 2015, the Canadian military reached out to ask if he could take the work done so far on stealth technology, and build on it.
He has now won the prestigious IEEE (Institute of Electrical and Electronics Engineers) Electromagnetics Award for his work on metamaterials and metasurfaces, and the creation of an 'invisibility cloak'.
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How does the cloak work?
Well, we 'see' an object, as Eleftheriades points out, when light hits it and scatters. Based on how the rays are scattered and reflected, we perceive shapes, colours, depth and distance.
His cloaking device emits waves of its own that cancel out the scattering as it occurs. (In this way, it is a bit like noise-cancelling headphones, which emit soundwaves to counter soundwaves.)
His device does this through the use of metamaterials, which are manmade materials designed to behave in ways that normal materials cannot. Fundamentally, they are built to control the flow of waves — radio, sound, light — in unprecedented ways.
The world's first metamaterial was created in the US in 2001, and research has sped up since. Key applications include lenses that can see more clearly, more refined diagnostic scans, vastly improved antennas and sensors… and 'invisibility cloaks'.
In the case of this last one, early efforts required bulky 3D structures, and though they did deceive radar they did not do it as effectively.
Eleftheriades's 'cloak' is a relatively elegant network of antennae, something like a circuit board, that sits on the surface of an object to be rendered invisible. As it interferes with incoming light waves, it forces them to bend or scatter differently, creating the impression that the object simply isn't there.
'We tried this first with a flat object and then with a cylinder,' he says. 'Both 'disappear' in that they cannot be seen by any radar system.'
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There's a lot the 'cloak' can do beyond hiding stealth weapons.
Metamaterials have already been used to make lenses that, for the first time in history, are flat and homogenous. Eleftheriades and his team have used such lenses to make super-microscopes that are 10 times as powerful as existing equivalents.
He and his team also recently developed a metasurface that could be placed along walls, to reflect radiowaves from cellphones and wi-fi routers in ways that magnify their strength and quality.
What about making something actually vanish from sight?
The closest he has come to doing this is when he put the 'cloak' on a car and had it zoom past speed sensors. It left no impression on the doppler-wave detectors at all. To the observer, of course, the car was moving past in plain view. Any chance that may change?
'The stuff you see in Star Trek, where something disappears behind a shield and is just gone… we're not there yet,' he says. 'That is worlds more complicated.'
Seeing is still believing, then… at least offline, and at least for now.
