The Smallest Switch

The Smallest Switch

Thursday, July 01, 1999
In the world of electronics, smaller is better. The ever-shrinking scale of circuitry accounts for the dizzying pace of improvement in everything from computers to boom boxes. Last year, Cees Dekker and his colleagues at the Delft University of Technology in the Netherlands took this process to a stunning extreme when they demonstrated the world's smallest working transistor—built from a lone molecule.

Fundamental to their work is the unusual molecule the researchers used. Called a carbon nanotube, it is a uniform lattice of interlinked carbon atoms, which are rolled up into a long, narrow tube just one billionth of a meter wide. Such nanotubes generally conduct electricity but, depending on how the tube is twisted, the molecules can behave either like freely conducting metals or like semiconductors (which sit somewhere between metals and electricity-blocking insulators).

Dekker was interested in the scientific aspects of the nanotubes, but when he began to think of them as techno-gadgets, "this opened up the route to demonstrating that man can build electronic devices out of a single molecule," he says. "The major thing was to recognize that you could use the semiconducting types of these nanotubes as transistors." His team succeeded in making a transistor with just one semiconducting nanotube as the active element. The molecular transistor performs much in the same way as traditional silicon-based devices, but in a fraction of the space. Transistors are the most basic devices for controlling current flow, so Dekker's triumph quickly fueled predictions of electronic devices, perhaps entire computers, built on a molecular scale.

Dekker emphasizes that they have produced merely the first prototype device based on a single molecule. Although it is "a technologically usable device," he says, there's still a long way to go. The next steps include finding ways to place the nanotubes at the right locations in an electronic circuit, probably by attaching chemical guides that bind only to certain metals.

FINALISTS Valuable Data Vault

Innovators: Larry Dalton, Frank Peter, Sandia National Laboratories

After 20 years of focusing on nuclear weapons security at Sandia National Laboratories, itÕs only natural that Larry Dalton should be safety-minded. He and Frank Peter, working with David Plummer, have turned their expertise to the growing problem of computer security, engineering a clever microscopic lock that blocks hackers.

Dalton and PeterÕs mechanical lock has notched wheels that turn from electronic impulses. Only the right combination allows access to protected information.

The Biological Machine

Innovator: Carlo Montemagno, Cornell University

In what looks like a vision from The Terminator, an engineer at Cornell has integrated living tissue with machinery.

In 1997, a team in Japan discovered that a protein called ATPase—the power source within cells—produces enough force to move a tiny device. Carlo Montemagno and his team set out to see if they could work ATPase into a biomolecular motor. First, they altered the proteins with chemical "handles" that bonded tightly with metals. Now they are trying to attach the molecules to a microscopic rotor. Fixing magnetic bars to the rotors could generate current to power a tiny machine that delivers drugs to cancer cells.
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