February R&D Round UpFebruary 8, 2008 By: Melanie Martella, Sensors
This month, tweaking nanotube conductivity, DNA pyramids that change shape, a microcontroller that takes low-power operation even lower, and synchronized prosthetics.
All Things Nano
NIST researchers have discovered that they can alter the conductivity of conductive polymers by changing how fast the polymer flows during processing. In some cases, adding even a small concentration of carbon nanotubes to a polymer will give you an electrically conductive plastic; vary the concentration of nanotubes and you can vary how much electricity the plastic will conduct. The researchers modified a shear rheometer to examine how the materials reacted to changing viscosities and discovered that, for a polymer with a given concentration of carbon nanotubes, the faster the polymer flows, the lower the conductivity. Once the flow is removed the nanocomposite reverts to its original conductivity. This finding may enable "tuning" of the material during processing.
According to the New Scientist article "Remote control DNA pistons could power tiny robots," Professor Andrew Turberfield at Oxford University and researchers at the University of Bielefeld in Germany have created nanoscopic DNA pyramids that can change shape when exposed to different chemical signals. They've managed to figure out how to get the DNA tetrahedrons to self-assemble and to flex when introduced to special DNA sequences. Essentially, some of the struts that make up the pyramid bind with these special DNA sequences and the resultant strut lengthens or contracts in response, causing the entire pyramidal cage to flex. One of the potential uses is to develop more sophisticated drug delivery systems since the cages can encapsulate proteins and release them on demand.
TI and MIT have teamed up to develop an ultra-low-voltage microcontroller. How low? The experimental version (unveiled this week at the International Solid State Circuits Conference) powers parts of the device at 0.3 V. The EE Times news article, "TI, MIT team to design ultra-low voltage chip", gives more detail, but the gist is that the design technique uses highly efficient onchip DC-to-DC conversion to run the circuitry that's normally most power hungry. This is a very big deal, especially to designers of portable devices, wireless sensor networks, and medical implants.
CNN has a lovely article ("Double amputee walks again due to Bluetooth") about leg prostheses for double leg amputees. A computer chip in each leg controls motors in the artificial joints to coordinate the motion of the knee and ankle. A Bluetooth receiver on each leg tells the other leg what it's doing, so that they can move in a coordinated fashion. As Marine Lance Cpl. Joshua Bleill says in the article, "They mimic each other, so for stride length, for amount of force coming up, going uphill, downhill and such, they can vary speed and then to stop them again". I'm sort of tickled by the fact that although this particular use of Bluetooth is extremely cool, the really neat bits are (as far as I'm concerned, anyway): a prosthetic leg with motorized joints, coordinated motion of knee and ankle, and the ability to synchronize the action of both legs to attain a more natural gait.
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