Contacts:
Stephen Chou,
University of Minnesota Electrical Engineering Dept.,
(612) 625-1316
Deane Morrison,
University News Service,
(612) 624-2346,
[email protected]
The Incredible Shrinking CD Gets Big Squeeze at U of Minnesota
A really compact disk, the size of a penny, that packs as much information as 30 current CDs could be on the horizon if technology developed by Stephen Chou becomes commercialized. The University of Minnesota electrical engineering professor has found a way to store 400 billion bits (or 400 gigabits) of information in a square inch of CD space; this is 800 times the storage capacity of current CDs, which carry only half a gigabit per square inch. The work appears in the current (Nov. 24) issue of Applied Physics Letters.
"This technology means disk drives can be made the size of a penny and mounted on one's wristwatch," said Chou. "As an example of the kind of information storage you could get, each current CD can hold 10 minutes of high-quality movies. But the penny-sized 'nano-CD' could hold five hours." Also, CAT-scan images, which now require copious amounts of CD storage space, would easily fit on a conventional-sized CD, Chou said.
The backbone of Chou's nano-CD technology is the ultra-small features that store each bit of information; merely 10 nanometers (billionths of a meter) wide and 40 nanometers apart. These features are 28 times shorter than features on current CDs; therefore, they occupy 800 times less area. To produce such small circuit patterns at an affordable cost, Chou has invented a new technology, called nanoimprint lithography, which represents a breakthrough in nanoscale patterning because of its simplicity, extremely low cost and high throughput (productivity). Nanoimprint uses a mold to stamp out patterns on softened polymers (reported in Science, 4/5/96). Traditionally, the patterns of a size like Chou's nano-CDs have to be made by radiating a polymer with electrons or X-rays--processes whose price tag puts them beyond the reach of all but a handful of places in the world. Chou calls nanoimprint lithography a "cookie cutter approach." The university has filed a patent on the technolo! gy.
Reading the information on nano-CDs also requires a special technique, since the nano-CD's feature size is nearly two orders of magnitude smaller than the wavelength of the laser light used in current CD players. Chou's team used a tiny needle to pick up information from the nano-CD surface, similar to the way the needle on a record player does except that Chou's needle does not completely touch the nano-CD. His team found that with a special method, called "tapping mode," a silicon needle can read a disk millions of times without causing significant wear.
Nanoimprint technology will have applications elsewhere, such as in microcomputer chip manufacturing, new materials, biology, chemistry and medicine, Chou said.
News releases also on WWW at http://www.umn.edu/urelate/news.html
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