New Scientist has a brief report on a team working toward making metamaterial threads that would be functionally invisible:
… fabricating metamaterials using components small enough to manipulate the sub-micrometre wavelengths of visible light is no mean feat. To avoid that problem, Tuniz’s colleagues Boris Kuhlmey, Simon Fleming and Maryanne Large have suggested an elegant way to shrink a larger metamaterial-like structure down to a size capable of controlling visible light: assemble standard glass rods and metal tubes into a cylinder, heat the assembly until it softens, and draw it into a long thin fibre. The process preserves the shapes of internal structures, but shrinks them down to the nanoscale needed to control visible light, and the resultant metamaterial is in the form of a thread that is thin enough to be flexible, like an optical fibre. So far, Tuniz and colleagues have produced 10-micrometre-thick threads.
Now, the researchers have used a computer model to design an invisible version of their thread. To achieve that, the thread must be just 1 micrometre thick – the metamaterial absorbs some light and so would appear dark if it was any thicker. Their calculations suggest that the thread would be invisible if seen from the side – rather than end on – in polarised light.
No promises of invisibility cloaks yet, sadly. But you never know…
Researchers in Hong Kong are developing technologies that could one day lead to hidden portals :
In the research paper, the researchers from the Hong Kong University of Science and Technology and Fudan University in Shanghai describe the concept of a “a gateway that can block electromagnetic waves but that allows the passage of other entities”
The gateway, which is now much closer to reality, uses transformation optics and an amplified scattering effect from an arrangement of ferrite materials called single-crystal yttrium-iron-garnet that force light and other forms of electromagnetic radiation in complicated directions to create a hidden portal.
Previous attempts at an electromagnetic gateway were hindered by their narrow bandwidth, only capturing a small range of visible light or other forms of electromagnetic radiation. This new configuration of metamaterials however can be manipulated to have optimum permittivity and permeability – able to insulate the electromagnetic field that encounters it with an appropriate magnetic reaction.
Whilst I’m not entirely sure how this metamaterial in supposed to behave, or what is meant by “other entities” in this context, such a substance has overtones of the Ringworld construction material described in Larry Niven‘s Ringworld series, which IIRC was impermeable to 40% of neutrino emissions, and under the application of a particular instrument would allow people to walk through it.
: The article is somewhat vague on how exactly this portal will work in reality, but I gather that it works either like a perfected “holographic mirror” that you can walk through, or else simply a glass-like sheet that can become reflective when required to. In any case
[from h+ Magazine][image from fdecomite on flickr]
A big part of the fun of this blogging gig (for me at least) is watching stories resurface and reiterate themselves over time. Point in case: metamaterials and ‘invisibility cloaks’, which cropped up a few times last year, and which raise their head again with news from Hong Kong University that researchers have discovered a theoretical method for not only making things appear invisible, but also for making one thing appear to be another thing entirely. Confused? Well, this might help:
The trick is to create a material in which the permittivity and permeability are complementary to the values in a nearby region of space containing the mouse we want to hide. “Complementary” means that the material cancels out the effect that the mouse has on a plane lightwave passing through. So a plane wave would be bent by the mouse but then bent back into a plane as it passes through the complementary material, making the mouse disappear.
The second step is to then distort this plane wave in the way that an elephant would. This means creating transformational material that distorts a plane lightwave in the same way as an elephant. So anybody looking at this mouse would instead see an elephant.
An invisibility cloak is just a special case of this, when the mouse is simply replaced by the illusion of free space, say Chan and co.
Simply? Well, they sound pretty sure of themselves, but I’ll maintain my skepticism until I see it actually working… or don’t see it, rather. [via SlashDot; image by crystalchu]
The intriguing development of materials that are effectively invisible thanks to a phenomenon called negative refraction continues apace.
This article from a Physorg has further details:
Applications for a metamaterial entail altering how light normally behaves. In the case of invisibility cloaks or shields, the material would need to curve light waves completely around the object like a river flowing around a rock. For optical microscopes to discern individual, living viruses or DNA molecules, the resolution of the microscope must be smaller than the wavelength of light
The theory behind negative refraction seems fairly complex – but it’s interesting to imagine what can be done by “altering how light normally behaves” and the possibility of viewing live viruses is also interesting.
[stories from Physorg and BBC News][image from PhoebeJ on flickr]
A group of mathematicians who previously worked on possible cloaking devices have found the same theory could be equally applied to create things resembling wormholes. The team uses mathematical theory to create ‘metamaterials’ that can bend and curve electromagnetic fields – like bending light to make something appear invisible.
The wormholes they describe aren’t quite the instantaneous transportation portals described by Star Trek or Valve’s new computer game. The light still travels through the metamaterial tube but isn’t detectable outside it, by sight or other methods. Uses for this idea include endoscopic surgery and 3D televisions where all but the end tips of many beams of light are hidden by the wormhole, giving the appearance of a floating image.
[image and link via ScienceDaily, image courtesy of Rochester University]