Japanese nanomachine first

TECHNOLOGY

Computers have been getting smaller since they were invented in the Forties. In the early days of computing, a typical machine might occupy an entire building. By the Sixties, the advent of transistors meant that computers could fit inside a single room (below). The microprocessor revolution in the Seventies paved the way for today's desktop and hand-held machines, which can have thousands of times the power and storage capacity of their gargantuan ancestors.

Now scientists are a step closer to producing microscopic computers. "Nanomachines" are devices that act on the microscopic or even molecular scale. A team of scientists in Japan has succeeded in making a binary switch - the fundamental working unit of any computer - out of a single molecule.

A report in this week's New Scientist outlines how the string-like molecules, of a chemical called azobenzene, can act as a locator for another molecule, cyclodextrin, that occupies one of two places - a binary "zero" or "one" - on the "string" depending whether the molecule is exposed to visible or ultraviolet light. The whole assembly, known as a rotaxane, was created by Naotoshi Nakashima and colleagues at Nagasaki University.

Jon McCleverty of Bristol University described the work as a "breakthrough", but added that practical applications may be some way off as thhe system takes several minutes to operate - millions of times slower than conventional electronic systems.

Michael Hanlon