DNA superlattices are the basis for invisibility cloaks and materials that can change their color
Researchers at Northwestern University have developed a new technology to produce metamaterials, materials whose surface is coated with nanostructures that give them unique and exotic optical properties. The key point of the new technology is nanoparticles attached to the surface by short chains of DNA molecules. These molecules, in response to certain external influences, can contract or lengthen, which allows you to change the color of the surface of the material or make it generally invisible in a certain range of the electromagnetic spectrum.
To create material with such an unusual structure, the researchers used lithography technology with the technology of DNA self-assembly. As a result, an ordered superlattice of nanoparticles held together by DNA molecules appears at the exit. “This approach allows nanostructures of almost any shape, type and size to be created on the surface of the material,” says Chad Mirkin, one of the researchers. “And some of this myriad of nanostructures cannot be produced using any of the existing technologies. “.
The creation of a superlattice begins with “drilling” holes in a polymer photoresist material, which is done using lithography technology. The sizes of these holes correspond approximately to the sizes of the used nanoparticles; they, these holes, are a kind of seats for nanoparticles. In the meantime, nanoparticles are being prepared, the surface of which is covered with short DNA strands, and when such nanoparticles are placed on the polymer surface, the second ends of the DNA strands are attached in a circle to the edges of the holes, seats.
The researchers used gold nanoparticles to create a prototype of the DNA metamaterial. When this material was exposed to solutions containing different concentrations of ethanol, the DNA strands changed their length, the nanoparticles moved away from the base surface and the color of the material changed from black to red, and then to green.
The researchers report that using the technology they have developed, it is possible to create metamaterials with an almost unlimited area, while maintaining a high accuracy of the location of nanoparticles on their surface. And by changing the size, shape and type of material of these nanoparticles, it is possible to obtain materials with almost any set of optical properties. Such materials can form the basis of medical sensors, environmental monitoring sensors, light conversion devices and concealment devices, which are commonly called the invisibility cloak.
Source: www.dailytechinfo.org