Now you see it: the reality of invisibility

Scientists worldwide are on a quest to make objects - and people - disappear.

Invisibility is one of the most startling technological wonders we will see in the future. The idea of a Harry Potter-style cloak of invisibility may be mind-bendingly hard to believe, but scientists say they are already well on the way to creating one.

Universities across the globe working in the rapidly expanding field of nanotechnology have demonstrated working prototypes, using new materials that can bend light around an object to make it, in effect, invisible.

Four months ago, boffins at the University of Singapore came up with something weirder and potentially even more frightening – a darkness beam that bathes objects in an absence of light, enabling invisibility to be projected from a distance.

It will come as no surprise that much of this research is being financed by the US military, which has already funded heat-seeking missiles, night-vision goggles and technology that can render tanks and aircraft undetectable to radar.

So how do you make something invisible? Basically, it relies on the way we see things. We perceive objects because light bounces off them into our eyes. Wavelengths of light produce the colours we see.

At least that’s how it worked until scientists started rearranging matter at a molecular level to make substances the world has never seen before – such as metamaterials.


A few years ago researchers created what they called negative index metamaterials that can bend light, and used them to curve light around an object so that it continues in a straight line on the other side, making the object invisible.

That proved Harry Potter’s cloak was possible, but there was a huge stumbling block: the stuff could only be made in tiny amounts, and it bent only one spectrum of light, so multiple layers would be needed for the entire spectrum. Creating large amounts seemed impossible, and the result could be too thick to be workable anyway.

A breakthrough came last month when scientists from Orlando’s University of Central Florida developed a multi-layer metamaterial that works across a wider spectrum of light, plus a nano-transfer printing system that can make bigger sizes.

The team’s leader, Dr Debashis Chanda, says the technique can print pieces about 10 centimetres square, which can then be joined together into larger sizes.

But there’s still a catch: currently the process only bends light in the red and blue spectrums. That would probably produce a green man rather than an invisible one, but there’s little doubt that science is on the edge of solving the problem. Military powers are pouring billions of dollars into such research, and according to the South China Morning Post, 40 invisibility projects have been bankrolled in China alone.

Although metamaterials seem the main contender, the University of Toronto has created invisibility by surrounding an object with small antennas that radiate an electromagnetic field to stop visible light from bouncing off it.

It will come as no surprise that much of this research is being financed by the US military.

The university’s Professor George Eleftheriades says the antennas could be printed and made flat, like a blanket or skin. ‘‘Instead of surrounding what you’re trying to cloak with a thick metamaterial shell, we surround it with one layer of tiny antennas, and this layer radiates back a field that cancels reflections from the object,’’ he says.

Another recent contestant, the darkness beam, sounds like something Darth Vader would happily swap his light sabre for. Using special lenses, a team led by National University of Singapore optical engineer Chao Wan, has in effect created a region of space in which the intensity of light is close to zero.

Think of it as a torch lens that would normally concentrate light at the centre of its beam, with the illumination gradually fading away into darkness. This system does the opposite. It focuses the darkness in the centre, and stops light from bouncing or ‘‘scattering’’ off any object inside what Wan calls the optical capsule in the middle.

‘‘A three-dimensional object placed in the optical capsule does not cause scattering, and one can therefore see the scene behind the object,’’ he says. ‘‘Such a huge three-dimensional light capsule is not a fantasy, it can be created using a 3D binary-optical system.’’

Although scientists have demonstrated that invisibility is possible, there has been no public debate about its inherent dangers and how the technology might be controlled.

Invisible soldiers are one thing, but history demonstrates that military equipment inevitably falls into private hands.

That grim possibility is something we might have to deal with sooner than we think.