Chemically assembled metamaterials may lead to superlenses

Nov 02, 2011 By Bill Steele
Two polymer molecules linked together will self-assemble into a complex shape, in this case a convoluted "gyroid." One of the polymers is chemically removed, leaving a mold that can be filled with metal. Finally the other polymer is removed, leaving a metal gyroid with features measured in nanometers. Credit: Wiesner Lab

(PhysOrg.com) -- Nanomanufacturing technology has enabled scientists to create metamaterials -- stuff that never existed in nature -- with unusual optical properties. They could lead to "superlenses" able to image proteins, viruses and DNA, and perhaps even make a "Star Trek" cloaking device.

Other metamaterials offer unique that could have applications in microelectronics or .

The limitation, so far, is that techniques like electron-beam lithography or atomic sputtering can only create these materials in thin layers. Now Cornell researchers propose an approach from chemistry to self-assemble metamaterials in three dimensions.

Uli Wiesner, the Spencer T. Olin Professor of Engineering, and colleagues present their idea in the online edition of the journal .

Wiesner's research group offers a method they have pioneered in other fields, using to self-assemble 3-D structures with nanoscale features.

A polymer is made up of molecules that chain together to form a solid or semisolid material. A block copolymer is made by joining two at the ends so that when each end chains up with others like itself, the two solids form an interconnected pattern of repeating geometric shapes -- planes, spheres, cylinders or a twisty network called a gyroid. Elements of the repeating pattern can be as small as a few across. Sometimes tri-polymers can be used to create even more complex shapes.

After the structure has formed, one of the two polymers can be dissolved away, leaving a 3-D mold that can be filled with a metal -- often gold or silver. Then the second polymer is burned away, leaving a porous metal structure.

In their paper the researchers propose to create metal gyroids that allow light to pass through, but are made up of nanoscale features that interact with light, just as the atoms in glass or plastic do. In this way, they say, it should be possible to design materials with a negative index of refraction, that is, materials that bend light in the opposite direction than in an ordinary transparent material.

Special lenses made of such a material could image objects smaller than the wavelength of visible light, including proteins, viruses and DNA. Some experimenters have made such superlenses, but so far none that work in the visible light range. Negative refraction materials might also be configured to bend light around an object -- at least a small one -- and make it invisible.

The Cornell researchers created computer simulations of several different metal gyroids that could be made by copolymer self-assembly, then calculated how light would behave when passing through these materials. They concluded that such materials could have a negative refractive index in the visible and near-infrared range. They noted that the amount of refraction could be controlled by adjusting the size of the repeating features of the metamaterial, which can be done by modifying the chemistry used in self-assembly.

They tried their calculations assuming the metal structures might be made of gold, silver or aluminum, and found that only silver produced satisfactory results.

Could these materials actually be made? According to graduate student Kahyun Hur, lead author on the paper, "We're working on it."

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User comments : 7

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Isaacsname
4 / 5 (1) Nov 02, 2011
:) They sort of look like sponges.
Cave_Man
2.5 / 5 (2) Nov 02, 2011
The ultimate path of this sort of research will be some sort of high energy assembly device that will be able to manipulate and create stuff from individual elements in highly precise quantities and chemical homogeneity.

I see them as being an extremely accurate emitter of all frequency at varying energy levels aligned so they can assemble in three dimensions using some kind of injected 'ingredient' plasma.

We could make super strong alloys with properties that are as varied as the possible number of chemical compounds which has been estimated at 10^18 to 10^200. We will truly be 'aliens' then.
gmurphy
not rated yet Nov 02, 2011
@Cave_Man, I like your vision of the future but frankly, we're not 'aliens' until we can navigate the stars, until then, we're just ambitious simians.
infiniteMadness
2 / 5 (1) Nov 03, 2011
"viruses" come on even my son knows its called "vira" in pluralis.
Osiris1
1 / 5 (1) Nov 03, 2011
Star drives will come too, when we can generate power with sufficient energy density. Further research into intraquark reactions will reveal yet another layer of increasingly small yet exponentially energetic force carriers of yet unknown forces that will help fill in the blank spaces on a new expanded standard model in three dimensions. One of these may and probably will be the force carrier for the gravitational and its opposite, dark energy depending of its 'charge'. Yet another if not the same will give rise to apparent mass.....yielding control of inertial forces in a moving craft. Handling the extra power required to activate access to these will be the largest problems of post nuclear energy production. Yuri Podkletnov was on to something and it is up to us to find out. Winner takes all! As long as we do not open some terrible gateway we will be fine. We either do it or someone else with less concern for safety will. Guts and vision versus beancounting.
Cave_Man
1 / 5 (1) Nov 05, 2011
Well if you've ever heard of the Roswell UFO fragment which is SUPPOSEDLY an impossibly assembled alloy of 99.9% silicon and some other metals like nickle and copper with non-terrestrial isotope ratios then you may tend to believe we aren't alone in the universe or on earth for that matter and that an outside source is fueling our technological development or at least guiding it toward a particular end.

But it's just as easy to believe this is an effect of the realization of the scale of our universe which leads us to study things which are both bigger and bigger and smaller and smaller.

I still think someone should hook that Roswell fragment up to a high precision power source and apply various currents and frequencies to it to see if it cloaks or something, that would really lend credence to the UFO theories.

Although the depth of conspiracy you can delve into is limitless, who knows if the fragment has been replaced with a fake or if the whole thing is manipulation...ahh life...
gmurphy
not rated yet Nov 09, 2011

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