Nanowire computer circuits debut

One of the big challenges to making cheap, lightweight, flexible electronic devices is developing simple, low-temperature methods of making high-performance circuits.

Researchers from Harvard University have found a way to paint molecular-size circuitry onto glass. The method is potentially very low-cost, and could eventually be used to make computer chips that pack extremely tiny and thus powerful circuits.

Because the tiny circuits can be painted on a non-crystalline substrate like glass or plastic, they could eventually be used in flexible electronic paper displays. Because the method is potentially inexpensive, the circuits are also appropriate for low-cost radio frequency tags, according to the researchers.

The researchers' prototype is a set of ring-oscillator circuits painted on glass. Ring oscillators are basic computer circuits. They convert direct current to alternating current via a self-sustaining feedback loop. The circuits run at 10 megahertz, or 10 million cycles per second. This is slower than silicon computer chips but faster than the plastic and non-crystalline silicon used in flexible electronics today, according to the researchers.

The circuits also have the potential to run in the gigahertz, or billions of cycles per second, range of telecommunications equipment, according to the researchers.

The roadblock to putting traditional electronics on glass or plastic is that these substrates break down at the high temperatures used to make crystalline silicon components.

The researchers made the circuits by flowing semiconductor nanowires into position on an insulating layer on a glass substrate. The nanowires serve as the channels, or signal carriers, all the device's transistors.

Using the method in practical applications requires making larger, more complex circuits than the researchers' proof-of-concept prototype. Practical applications could be possible within five years, according to the researchers.

The work appeared in the April 28, 2005 issue of Nature (High-Speed Integrated Nanowire Circuits).