The nanotechnology research field is pretty fertile these days. Researchers at Harvard recently showed a nanowire which could be the next big diagnostic tool for doctors. Meanwhile, University of Southern California scientists have developed a 'nanosensor' that only works when noise is added. And another Harvard team has developed nanoscale fibers that are thinner than the wavelengths of light they carry.
Here are some details about the next future diagnostic tool.
A tiny nanowire sensor -- smaller than the width of a human hair, 1,000 times more sensitive than conventional DNA tests, and capable of producing results in minutes rather than days or weeks -- could pave the way for faster, more accurate medical diagnostic tests for countless conditions and may ultimately save lives by allowing earlier disease detection and intervention, Harvard scientists say.
One of a growing number of promising diagnostic tools that are based on nanotechnology, the silicon sensor represents the first example of direct electrical detection of DNA using nanotechnology, according to the researchers. The sensor and the detection of the CF (cystic fibrosis) gene will be described in the Jan. 14 issue of the journal Nano Letters.
"What one could imagine," says study leader Charles M. Lieber, a professor of chemistry at Harvard, "is to go into your doctor's office, give a drop of blood from a pin prick on your finger, and within minutes, find out whether you have a particular virus, a genetic disease, or your risk for different diseases or drug interactions."
Lieber is also a member of the Scientific Advisory Board of Nanosys Inc. and was already featured on this blog in "Better Displays With New Nanowire Film."
Now, let's turn our attention to the USC nanotube device that needs added noise to detect signals.
The device uses a novel kind of transistor made from carbon nanotubes. The principal investigator, Professor Bart Kosko of the USC department of electrical engineering, claims that the series of experiments reported in the December issue of the American Chemical Society's Nano Letters, says the result is significant both in the development of electronic applications for nanotubes, and in the development of applications for "stochastic resonance," the counterintuitive use of noise to amplify signals.
The basic idea of stochastic resonance detection, says Kosko, is to create devices with strict threshold effects, that only respond to signals of more than a certain amplitude -- and then set this threshold around, or even below the amplitude of the signal expected.
But what will we do with these nanotubes?
Twisting such tubes can drastically change their electronic properties, from conductors, to semiconductors. A main focus of interest now is their use in flat panel displays.
Kosko believes that increased awareness of the stochastic resonance phenomenon can aid designers of communications, including especially modern spread-spectrum devices, which often rely on an array of faint signals.
"Nano-device designers can individually tailors nanotubes to specific signals and then deploy them in numbers -- rather like pipe organs tuned to different notes -- to take advantage of the SR-effects, " he said.
Our last discovey for today is about nanoscale fibers made from silica and developed by a team led by Eric Mazur from Harvard University.
Researchers have developed a process to create wires only 50 nanometers (billionths of a meter) thick. Made from silica, the same mineral found in quartz, the wires carry light in an unusual way. Because the wires are thinner than the wavelengths of light they transport, the material serves as a guide around which light waves flow. In addition, because the researchers can fabricate the wires with a uniform diameter and smooth surfaces down to the atomic level, the light waves remain coherent as they travel.
Below is a stunning picture of such a silica nanowire wrapping a beam of light around a strand of hu-man hair (Credit: Limin Tong/Harvard University). You'll find additional pictures on this NSF page.
The smaller fibers will allow devices to transmit more information while using less space. The new material may have applications in ever-shrinking medical products and tiny photonics equipment such as nanoscale laser systems, tools for communications and sensors. Size is of critical importance to sensing -- with more, smaller-diameter fibers packed into the same area, sensors could detect many toxins, for example, at once and with greater precision and accuracy.
The Mazur research group has also been mentioned previously here in "Femtosecond Lasers for Nanosurgery."
Sources: American Chemical Society, December 16, 2003; University of Southern California, December 16, 2003; National Science Foundation, December 17, 2003; all via EurekAlert!
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