Thursday, May 31, 2007

Practical Nanowire Devices

Continued from page 1

By Kevin Bullis

To demonstrate the usefulness of the technique, the researchers transferred the films to silicon wafers, then used conventional techniques to deposit electronic contacts on the films. The nanowires bridged the contacts, serving as semiconducting channels for working transistors.

Lieber says that early applications could include accurate home tests for illnesses such as cancer, influenza, and sexually transmitted diseases. In such a device, a protein biomarker for prostate cancer, for example, would connect to the nanowires, changing the wires' conductivity and registering the protein's presence. Nanowires provide three-orders-of-magnitude-greater sensitivity than current tests, Lieber says. And because the nanowires directly detect the proteins by generating an electronic signal, such tests would provide results right away, making it unnecessary for researchers to wait for results to come back from the lab. What's more, tests for multiple biomarkers can easily be combined on a chip. An array of hundreds of nanowires, each chemically modified to react with a specific protein, could be used to create a highly accurate cancer test.

The nanowires could also be used in flexible displays to turn pixels on and off. Conventional high-speed transistors require fabrication temperatures that would melt the plastic substrates used in flexible displays. But nanowires can provide the same performance without the need for high temperatures.

The researchers are now studying the process to find ways of packing the nanowires closer together, which could allow for applications beyond those for sensors and displays, such as for memory. Before the process can be used for manufacturing, though, it will need to be automated, possibly in ways similar to the blown-bubble techniques now used for high-volume production of plastic bags. Lieber says that the method could be used in nanodevice manufacturing within one to two years.