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The logic to molecular computers.

Every pocket calculator or personal computer needs at least one thing to do its job: a logic system. A basic component of such microelectronic systems is the information gate, which takes in some signals and sends others out. Some gates open or close to allow signals through; others select one of two pathways, A "or" B, for a signal to travel along; a third kind opens both routes, A "and" B.

"And" gates are critical. No computer can run without them.

Breaking new ground in this area, a team of chemists from Queen's University in Belfast, Northern Ireland, led by A. Prasanna de Silva, reports in the July 1 NATURE the fabrication of a single molecule that behaves as an "and" gate in a logic circuit. The molecule, an anthracene derivative called benzo-15-crown-ether-aldehyde, fluoresces, or emits light of one wavelength, when exposed to light of another.

The molecule can function as an "and" gate because it reacts differently to two inputs: hydrogen ions and sodium ions. The intensity of this molecule's fluorescence varies, depending on whether a signal comes from the hydrogen channel, the sodium channel, or both. When both channels provide input, the molecule radiates at a stronger intensity, clearly signaling that channel 1 and channel 2 are both on.

This technology offers the promise that single molecules could replace whole electronic components, such as transistors. Whereas microelectronic devices use electric currents and voltages to process information, a molecular system uses charges and light. In theory, a cluster of molecules could replace an entire computer chip, says Leonard F. Lindoy of James Cook University of North Queensland in Townsville, Australia. Since molecular devices are more compact and less linear than conventional integrated circuits, they could facilitate better parallel processors. The result may be smaller, faster, more efficient computers.
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Title Annotation:single molecule used as "and" gate in logic circuit
Publication:Science News
Article Type:Brief Article
Date:Jul 24, 1993
Words:299
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