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.
The research was supported by the Air Force Office of Scientific Research and by the Army Research Office's Multidisciplinary University Research Initiative (MURI).
The other members of the team were first author Antoine Moreau, Clermont University, France; Duke's Ryan Hill, Jack Mock, Benjamin Wiley and Ashutosh Chilkoti; and Qiang Wang from the Capital Normal University, Beijing.
"Controlled-reflectance surfaces with film-coupled colloidal nanoantennas," A. Moreau, C. Ciraci, J. Mock, R. Hill, Q. Wang, B. Wiley, and A. Chilkoti. Nature, 6 Dec., 201
Richard Merritt | Source: EurekAlert!
Further information: www.duke.edu
More articles from Physics and Astronomy:
“Out of This World” Space Stethoscope Valuable on Earth, Too
22.05.2013 | Johns Hopkins
Storms on Uranus, Neptune Confined to Upper Atmosphere
21.05.2013 | University of Arizona
A fried breakfast food popular in Spain provided the inspiration for the development of doughnut-shaped droplets that may provide scientists with a new approach for studying fundamental issues in physics, mathematics and materials.
The doughnut-shaped droplets, a shape known as toroidal, are formed from two dissimilar liquids using a simple rotating stage and an injection needle. About a millimeter in overall size, the droplets are produced individually, their shapes maintained by a surrounding springy material made of polymers.
Droplets in this toroidal shape made ...
Frauhofer FEP will present a novel roll-to-roll manufacturing process for high-barriers and functional films for flexible displays at the SID DisplayWeek 2013 in Vancouver – the International showcase for the Display Industry.
Displays that are flexible and paper thin at the same time?! What might still seem like science fiction will be a major topic at the SID Display Week 2013 that currently takes place in Vancouver in Canada.
High manufacturing cost and a short lifetime are still a major obstacle on ...
University of Würzburg physicists have succeeded in creating a new type of laser.
Its operation principle is completely different from conventional devices, which opens up the possibility of a significantly reduced energy input requirement. The researchers report their work in the current issue of Nature.
It also emits light the waves of which are in phase with one another: the polariton laser, developed ...
Innsbruck physicists led by Rainer Blatt and Peter Zoller experimentally gained a deep insight into the nature of quantum mechanical phase transitions.
They are the first scientists that simulated the competition between two rival dynamical processes at a novel type of transition between two quantum mechanical orders. They have published the results of their work in the journal Nature Physics.
“When water boils, its molecules are released as vapor. We call this ...
Researchers have shown that, by using global positioning systems (GPS) to measure ground deformation caused by a large underwater earthquake, they can provide accurate warning of the resulting tsunami in just a few minutes after the earthquake onset.
For the devastating Japan 2011 event, the team reveals that the analysis of the GPS data and issue of a detailed tsunami alert would have taken no more than three minutes. The results are published on 17 May in Natural Hazards and Earth System Sciences, an open access journal of ...
22.05.2013 | Life Sciences
22.05.2013 | Ecology, The Environment and Conservation
22.05.2013 | Earth Sciences
17.05.2013 | Event News
15.05.2013 | Event News
08.05.2013 | Event News