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A carbon nanotube integrated circuit, with a thousand nanotubes acting like transistors, has been devised by Phaedon Avouris of IBM. Nanometer-wide tubes made of carbon chickenwire have for some years been expected to become an active ingredient in electronics. Besides their strong mechanical properties, nanotubes have a variety of useful electrical properties. Nanotubes, for example, can sustain current densities hundreds of times greater than those of common metals and are created in both metallic and semiconducting form. Speaking at the APS March meeting in Seattle, Avouris described how, in a mixed batch of nanotubes, one can short out the metallic nanotubes (with a surge of voltage) while leaving the semiconducting ones intact for use as circuit elements.
Other nanotube highlights from the same meeting:
Aiming to detect cancers early, safely, and inexpensively, Britton Chance of the University of Pennsylvania and his colleagues have created "molecular beacons," tiny capsules that are opened by specific biochemical activity related to a tumor. At the APS March Meeting, Chance described molecular beacons designed to detect 1-2 mm sub-surface breast tumors inexpensively and without ionizing radiation. Injected into the body, the capsules remain sealed until opened by specific enzymes associated with breast cancer. The beacons then fluoresce near-infrared light in response to light beaming from a small device outside the body. That same device then detects the signal from the beacons. (The beacons emit enough near-infrared light so that some of it gets through the body.) The device is designed to cost only several thousand dollars, Chance said, and is based on off-the-shelf CD and cell-phone technology. The molecular beacon has successfully been tested in mice, and human tests are planned. The technique does not require uncomfortable compression of the breast, which is what often is required for women under 40 years of age who receive mammograms. Self-tests for breast cancer may eventually be possible with this technique, Chance said.
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