This article illustrates research and development work in nanotechnology for manufacturing computers at the molecular level. Computers have gone from large and mechanical, like Babbage's Difference Engine, to molecular. Researchers have shown that carbon nanotubes can be strung across electrodes to make minute transistors. Beyond sheer density of data, the nanotube chips have another, perhaps even more important, potential advantage over their electronic rivals: the memory does not disappear when the power goes off. The tubes may be drawn to the electrode by an electrical attraction, but they are held there by van der Waals attraction, a sort of molecular-level suction. In that way, an electromechanical memory chip will have more in common with a computer hard drive or floppy disk than with random access memory. Physicist Paul McEuen and his colleagues at Cornell have fabricated a transistor that passes signals through a single atom.
Computing intercorrelations of tests on the adding machine.