Research is progressing apace to develop new types of memory to meet the enormous demand for storage expected to be triggered by the multimedia revolution, and chemists at the Georgia Institute of Technology have identified trigger molecules that are changed when exposed to polarized light, then changed back when exposed to unpolarized light. Circularly-polarized light would be used for writing, linearly-polarized light for reading and unpolarized light for erasing. The system uses chiral molecules – ones that exist in both right- and left-handed versions, so that when right-handed molecules meet left-handed light, they are altered preferentially over left-handed ones. If the chiral molecules are dissolved in liquid crystal, the change can be used to cause a phase transition that can be detected by passing linearly- polarized light through the crystals. The researchers believe this could be used to create three-dimensional liquid crystal data storage devices. The findings were described to the American Chemical Society at its meeting in New Orleans last week by Gary Schuster, a professor of organic chemistry at Georgia Tech. The researchers have so far demonstrated the technique only in two dimensions, but have ideas for converting to three. A weakness is that the trigger molecules produced to date can only be switched at most a few hundred thousand times before they stop responding. But photochemically-switched storage is seen as promising short- term bulk storage for items like a movie or an entire newspaper, downloaded overnight for short-term viewing, after which the memory would be cleared for tomorrow’s material.
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