A Purdue-based startup is developing high-temperature “plasmonic metamaterials” that could dramatically increase data-storage capabilities, improve solar-cell and waste-heat recovery performance and provide a new avenue for clinical therapeutics.
The plasmonic metamaterials, which are man-made composites of metals with engineeredoptical properties, are being developed to create novel optical nanodevices.
The technology, which is being commercialized by Nano-Meta Technologies Inc., was developed in the laboratories of Vladimir Shalaev [pronounced SHA-la-eve], distinguished professor of electrical and computer engineering and the company’s scientific director, and Alexandra Boltasseva [pronounced BOL-ta-see-va], associate professor of electrical and computer engineering and chief research and development scientist for Nano-Meta Technologies.
“What is promising about this technology is its ability to harness ‘surface plasmons.’ Doing that enables us to do more than control light – we can manipulate it,” Shalaev said. “As we guide or route the light at the nanoscale level, we can develop more powerful microscopes, more efficient thermophotovoltaic solar cells, increase data storage and improve medical treatments.”
Nano-Meta Technologies has licensed the technology through the Purdue Office of Technology Commercialization. A video about the company can be viewed at: http://youtu.be/k086r6zfIOE
Boltasseva said the company is able to tailor the plasmonic metamaterials for different applications by using their patented processes in material fabrication and development.
“We are doing this by tailoring the materials to optimize their properties and making nanoscale unit cells,” she said. “For example, to increase data-storage densities we are developing new materials for heat-assisted magnetic recording capability, which uses heat to record data on a magnetic disk.”
The materials also could be used for solar thermophotovoltaics to improve solar-cell efficiency. Current solar cells have an efficiency of about 15 percent. In theory the efficiency might be improved to as high as 85 percent with solar thermophotovoltaics. The plasmonic layer acts as a thin “intermediate spectral converter” that absorbs the entire spectrum of sunlight and then illuminates the solar cell at the selected optimized wavelength, thereby dramatically increasing the solar-cell productivity.
The spectral converter is an extremely thin layer of metamaterial that uses plasmonic nanoantennas to absorb and emit light. The layer might be as thin as 500 nanometers, or half of a micron, roughly one-hundredth the width of a human hair. This layer of material would be heated by sunlight to about 1,500 degrees Celsius.
Thermophotovoltaic technology can also be applied as a waste heat recovery method, where the radiation from high temperature objects such as an industrial furnace, or a vehicle engine is spectrally engineered to match photovoltaic cell bandgap, leading to high efficiency energy conversion from heat that is wasted otherwise.
The challenge Nano-Meta is resolving that can make the optical technologies more applicable to various uses is by replacing the conventional use of gold and silver in the plasmonic components because these metals cannot withstand high temperatures.
“We are using, for example, titanium nitride and zirconium nitride because these materials have exceptional strength and can withstand the high temperatures needed for performance and efficiency,” said Urcan [pronounced Ooor-Jon]Guler [pronounced Gooler], postdoctoral research associate working with Shalaev and Boltasseva and a chief scientist for Nano-Meta Technologies. “But we also have identified other classes of materials for specific optical applications including transparent electrically conducting oxides and graphene-ultrathin layers of carbon.”
