Microscopic metallic cubes could unleash the enormous potential of metamaterials to absorb light, leading to more efficient and cost-effective large-area absorbers for sensors or solar cells, Duke University researchers have found.
Metamaterials are man-made materials that have properties often absent in natural materials. They are constructed to provide exquisite control over the properties of waves, such as light. Creating these materials for visible light is still a technological challenge that has traditionally been achieved by lithography, in which metallic patterns are etched onto an inert material, much like an ink-jet printer.
As effective as lithography has been in creating such structures, it does have a limitation – it is very expensive and thus difficult to scale up to the large surface areas required for many applications.
"Our new approach is more of a bottom-up process," said Cristian Ciracì, research scientist at Duke's Pratt School of Engineering. "It may allow us to create devices – such as efficient solar panels – that cover much larger areas. In our experiments, we demonstrated an extraordinarily simple method to achieve this."
The results of Ciracì and co-workers' experiments, which were conducted in the laboratory of senior researcher David R. Smith, William Bevan Professor of electrical and computer engineering at Duke, were published Dec. 6 in the journal Nature.
For many applications or devices, the key is the material's ability to control the absorption of electromagnetic waves. Metals, for example, can be highly reflective on their own, which may be beneficial for some applications, but for something like a solar cell, optimal light absorption is desired.
"However, metamaterials based on metallic elements are particularly efficient as absorbers because both the electrical and magnetic properties of the material can be controlled by how we design them," Ciracì said.
The new metamaterial developed by the Duke team has three major components – a thin layer of gold film coated with a nano-thin layer of an insulator, topped off with a dusting of millions of self-assembled nanocubes. In the current experiments, the nanocubes were fabricated out of silver.
"The nanocubes are literally scattered on the gold film and we can control the properties of the material by varying the geometry of the construct," Ciracì said. "The absorptivity of large surface areas can now be controlled using this method at scales out of reach of lithography."
While metals on their own tend to have reflective properties, the nanocubes act as tiny antennae that can cancel out the reflectance of the metal surface.S
"By combining different components of the metamaterial elements together into a single composite, more complicated reflectance spectra could be engineered, achieving a level of control needed in more exotic applications, such as dynamic inks," Ciracì said.
Duke University: http://www.duke.edu
This press release was posted to serve as a topic for discussion. Please comment below. We try our best to only post press releases that are associated with peer reviewed scientific literature. Critical discussions of the research are appreciated. If you need help finding a link to the original article, please contact us on twitter or via e-mail.
Institute for Highway Safety is known for crash-test safety ratings, but as cars get smarter there's a need to look beyond crashworthiness
Researchers have long struggled to resolve what happens to information when it falls inside a black hole, but the famous physicist says he has a solution
Researchers have been using muons to take a peek inside the nuclear reactors in Japan that melted down in 2011. The results could aid the continuing cleanup operations.
Neutrinos, created by violent phenomena such as black holes and exploding stars, could hold the key to the universe’s most distant and mysterious events
Better MRI scanners could result from a trick in which a magnetic field springs up from nowhere, using materials famous for their link to invisibility cloaks
Water locked away in rocks for 1.5 billion years reveals conditions were right for complex organic molecules to form in deep sea hydrothermal vents
Helium, used in nuclear, medical and, yes, party industries, has become scarce, but new research has revealed a possible way to pinpoint fresh sources
New lab results show how collisions between comets and planets can make the molecules that are the essential building blocks of life.
A startup company says it is expanding the language of DNA to create new tools for drug discovery.
If scientists can convince people to use the app, they hope it will help them solve a cosmic mystery. This story originally aired on March 27, 2015 on All Things Considered.