As cell phones and computers continue to shrink, many companies are seeking better ways to store hundreds of gigabytes of data in small, low-power devices. A special type of liquid crystal (similar to those used in computer displays and televisions) offers a solution and lasers can encode data throughout a liquid crystal known as holographic storage, the technique makes it possible to pack much more information in a tiny space.
But attempts to use liquid crystals for data storage have had limited success. In order to reliably record and rewrite data, researchers must figure out a way to uniformly control the orientation of liquid crystal molecules as the most liquid crystal technologies currently rely on physical or chemical manipulation, such as rubbing in one direction, to align molecules in a preferred direction.
In an important advance, scientists at the Tokyo Institute of Technology have created a stable, rewritable memory device that exploits a liquid crystal property called the "anchoring transition". Researchers demonstrated memory and rewritable bistable devices based on an anchoring transition of a nematic liquid crystal on a perfluoropolymer surface. Spontaneous orientation changes between planar and homeotropic occur on cooling and heating with a large temperature hysteresis. Orientation switching also occurs by applying an electric field with a response time of several milliseconds depending on the field strength claims the researchers.
Using either a laser beam or an electric field, the researchers can align rod-like liquid crystal molecules in a polymer. Their tests show that the liquid crystal created by the team can store data, be erased and used again...
"This is the first rewritable memory device utilizing anchoring transition," said Hideo Takezoe, who led the research. And because the device is bi-stable -- the liquid crystals retain their orientation in one of two directions -- it needs no power to keep images, adds Takezoe.
Ref : http://jap.aip.org/japiau/v107/i12/p123108_s1?isAuthorized=no
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