Lighting the nanoworld with nanolamps
An interdisciplinary team of researchers at Cornell University (CU) has built 'nanolamps.' These extremely small light bulbs are made of light-emitting nanofibers about the size of a virus or the tiniest of bacteria. Using a technique called electrospinning, the researchers spun the fibers from a metallic element, the ruthenium, and a polymer. These nanofibers "are so small that they are less than the wavelength of the light they emit." Apparently, these nanofibers are easy to produce. But before they can be integrated into our increasingly smaller electronic devices, there still is a need to know how long these nanolamps can last.
This research project needed the collaboration of nine CU researchers, including George Malliaras, associate professor of materials science and engineering and director of the Cornell NanoScale Facility, and Harold Craighead, professor of engineering and director of the National Science Foundation-funded Nanobiotechnology Center. The Craighead Research Group provided the electrospinning technique used to create these glowing nanofibers.
Below is a closeup of such an electrospun fiber. "During experimentation the organic devices gave off an orange glow." (Credit: Craighead Research Group) This image was picked from an article from Anne Ju in the Cornell Chronicle, "CU researchers create 'nanolamps'" (April 11, 2007).
Here are some more details about how these nanofibers are produced.
Using a technique called electrospinning, the researchers spun the fibers from a mixture of the metal complex ruthenium tris-bipyridine and the polymer polyethylene oxide. They found that the fibers give off orange light when excited by low voltage through micro-patterned electrodes -- not unlike a tiny light bulb. "Imagine you have a light bulb that is extremely small," said Malliaras, an organic materials expert. "Then you can use the bulb to illuminate objects that you wouldn't be able to see otherwise."
José M. Moran-Mirabal, an applied physics Ph.D. student working in Craighead's laboratory, says the technique "can be compared with pouring syrup on a pancake on a rotating table." [Note: how often do you do this?] Here are his explanations.
As the syrup is poured, it forms a spiraling pattern on the flat pancake, which in electrospinning is the substrate with micropatterned gold electrodes. The syrup would be the solution containing the metal complex-polymer mixture in solvent. A high voltage between a microfabricated tip and the substrate ejects the solution from the tip, Moran-Mirabal said, and forms a jet that is stretched and thinned. As the solvent evaporates, the fiber hardens, laying down a solid fiber on the substrate.
For more information, this research work has been published in Nano Letters under the name "Electrospun Light-Emitting Nanofibers" (Volume 7, Number 2, Pages 458-463, February 2007). Here is a link to the abstract.
Sources: Cornell University News Service, via EurekAlert!, April 11, 2007; and various websites
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