The invisibility cloak Harry Potter brandishes against dark lords and nosy professors is now a reality—at least in microwave light. Duke University engineer Yaroslav Urzhumov has designed a plastic disk that makes a small object placed in its hollow center invisible to frequencies from 9.7 to 10.1 GHz (close to the range used by radar speed guns). Holes in the doughnut-shaped cloak can eliminate an object's shadow and decrease its ability to scatter light. In effect, the cloak guides the microwave beams around the object so they can't bounce back—rendering it invisible. Until scientists can scale up, however, it might be useful only for getting toy cars out of a speeding ticket.
Time: 3 to 8 hours
Cost: About $100
Difficulty: 1 out of 5
1. Find a 3-D printer, preferably one that builds objects in thin layers of plastic (a process called fused deposition modeling). If you don't own a 3-D printer, can't borrow one, or lack the funds to buy one—typically $500 or more—you can pay an online company (such as Shapeways or RedEye on Demand) to print a design for you.
2. Download Urzhumov's design file at here and print it out. (The default thickness is 1 centimeter, but it can expand as tall as a 3-D printer allows.)
3. To use the invisibility cloak, line the disk's inner ring with aluminum foil, lay it on a flat surface, and put an object 5.4 inches long or less inside. Any microwaves shining on the disk's outer edge won't reveal your precious property.
Before accessing Urzhumov's 3-D-printing file, please note: Urzhumov and his colleagues retain the copyright to the work, and by downloading this file you agree: 1) to take full responsibility for the consequences of using it; and 2) to indemnify Duke university and all individuals involved in the creation of this work of art—as well as Popular Science and its parent company, Bonnier Corp.—from any and all claims of damage against them. (That said, you can download the file here.)
This article originally appeared in the September 2013 issue of Popular Science.
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Ya good luck getting the real file. However the way cloaking works is by creating a hole that is the same size as the wavelength of light that you are trying to reflect. The loophole in the law of optics is that you can create holes this small now that can then reflect the same wavelength back in the direction it came into the material. This is how cloaking works. This can be done on any visible wavelength, as well as, infrared, microwave, etc. Creating holes that are that small can be challenging and some require the use of new erosion techniques. Ideally, in order to create a full spectrum cloak, the material that contains your small holes would be very transparent. This would allow for multiple layers of the light filters to be staked upon one another and still allow the light to reflect through the stacked layers. Of course, this is a laymen theory but doing this with thin holographic layers does seem like a good possibility. For single layer materials, that have a large wavelength, a 3-D printer will do. Anything smaller and erosion or holograms must be used.
Good luck getting that file. Also, in order to create cloaks in other wavelengths, visible light for instance, you need to be able to create holes that are as small as the wavelength of light that you are trying to reflect. The loophole in the law of optics is simple : You can bend light back on itself, in the same wavelength. This means that you can catch the wavelength and then loop it back in the same direction it came or, any direction for that matter. To do this in smaller wavelengths you need some complex erosion techniques that wouldnt be able to be done by an average DYI'er.
If you could however, doing this in thin transparent layers (perhaps holograms) would allow you to stack layers of holes for different wavelengths of light. This compounding effect might allow for the ability to combine layers for a multi-spectrum cloak. This would be a technology that no one would want you to have. Creating a full spectrum cloak would make even nuclear warheads invisible. I imagine this will be a closely guarded secret if it is done successfully.
However, thanks to Moore's law, and the need to stop bleeding of electric currents through microprocessor channels, the ability to create small nano-scale holes will become more prevalent. Thus the chance of creating materials that could do the job.
"Do not try and bend the spoon. That is impossible. Only try and realize the truth - there is no spoon."