Soon, an aluminium foil lamp that outshines incandescent lights
Washington | June 05, 2007 3:24:46 PM IST
Researchers at the University of Illinois, US, are developing thin, lightweight panels of microcavity plasma lamps that can be used for residential and commercial lighting, and for certain types of biomedical applications.
"Built of aluminum foil, sapphire and small amounts of gas, the panels are less than one millimeter thick, and can hang on a wall like picture frames," said Gary Eden, a professor of electrical and computer engineering at the university and corresponding author of a paper describing the microcavity plasma lamps in the June issue of the Journal of Physics D: Applied Physics.
Like conventional fluorescent lights, microcavity plasma lamps are glow-discharges in which atoms of a gas are excited by electrons and radiate light. However, they also produce the plasma in microscopic pockets and hence require no ballast, reflector or heavy metal housing.
As such, the panels are lighter, brighter and more efficient than incandescent lights and scientists believe that with further engineering, will approach or surpass the efficiency of fluorescent lighting.
According to Prof. Eden, the plasma panels are also six times thinner than panels composed of light-emitting diodes.
A plasma panel consists of a sandwich of two sheets of aluminium foil separated by a thin dielectric layer of clear aluminium oxide (sapphire). At the heart of each lamp is a small cavity, which penetrates the upper sheet of aluminium foil and the sapphire.
According to lead author of the paper and visiting research scientist Sung-Jin Park, "each lamp is approximately the diameter of a human hair".
"We can pack an array of more than 250,000 lamps into a single panel," said Park.
A glass window, 500 microns (0.5 millimetres) thick, completes the entire panel assembly.
The window's inner surface is coated with a phosphor film 10 microns thick, bringing the overall thickness of the lamp structure to 800 microns, Park added.
As of now, the team has fabricated flat panels with radiating areas of more than 200 square centimetres, and depending upon the type of gas and phosphor used, uniform emissions of any colour can be produced, the scientists said.
In preliminary, values of the efficiency - known as luminous efficacy - of 15 lumens per watt were recorded, and upon optimisation of the array design and microcavity phosphor geometry, values exceeding 30 lumens per watt are expected, said Prof. Eden.
In comparison, a typical incandescent light has an efficacy of 10 to 17 lumens per watt, he said.
The team has also demonstrated flexible plasma arrays sealed in polymeric packaging.
According to the scientists, these devices offer new opportunities in lighting, in which lightweight arrays can be mounted onto curved surfaces - on the insides of windshields, for example.
The flexible arrays could also be used as photo-therapeutic bandages to treat certain diseases - such as psoriasis - that can be driven into remission by narrow-spectrum ultraviolet light, they said. (ANI)
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