Looking past silicon to carbon nanotubes.
Eventually, semiconductor manufacturers wont be able to cram any more transistors onto silicon chips. So Jia Chen is working on an alternative: electronic circuits and devices that use cylindrical, nanometer-wide carbon molecules called carbon nanotubes. Among their other advantages, some types of nanotubes can conduct electricity 100 times better than silicon. So far, most transistors made out of carbon nanotubes have been p-type, meaning they use positive charge carriers; negative – n-type – nanotube transistors have been much more difficult to produce. Chen, however, has found a simpler way to make them, which could be an important step toward integrating carbon nanotubes into conventional electronics. Chen discovered that attaching certain kinds of molecules to nanotubes would add electrons to them or draw electrons out, yielding either p- or n-type devices. Another problem with nanotube transistors is their need for metal electrodes, which are necessarily much larger than the nanotubes. The size difference tends to cause current leakage, reducing electrical efficiency. Chen found she could add certain impurities to a small segment of a nanotube to allow the nanotube to serve as an electrode, but one with little leakage. Her nanotube transistors carried 100 times as much electrical current as previous ones. The properties of nanotubes vary depending on their diameters. Choosing a particular diameter causes a tube to emit light at a particular wavelength. Chen was able to control the positive and negative charges in a nanotube to make it emit light 100 times brighter than the light from earlier devices. This could give nanotubes the ability to serve as optical interconnects – transmitting data among circuits more efficiently than copper does. Eventually, every device on a chip could be made from nanotubes. “Imagine a circuit with the same material acting as sensors, transistors, light emitters, and also interconnects,” says Chen.
Making tiny mirrors for laser beams
Vladimir Aksyuk made a name for himself in the world of microelectromechanical systems in 1999 when he spearheaded the development of Bell Labs all-optical switch – the first commercial device to use thousands of tiny rotating mirrors to intricately manipulate optical communications signals without converting them into electrical pulses and back. Its performance was 16 times faster than that of the best of its electrical counterparts. Aksyuk has since expanded on that technology to create systems featuring arrays with mirrors as small as 100 micrometers across, each one capable of not only rotation but also up-and-down motion. These arrays enable extremely precise control of laser beams, which is crucial to the U.S. militarys program to develop a secure, high-bandwidth laser communication system for aircraft, ground bases, and even space vehicles. The arrays may also soon change how microchips are produced. The Russian-born Aksyuk is heading a project at Bell Labs to use micromirrors to carve out microchips without the costly “masks” – basically, stencils patterned with circuit designs – that are currently used to optically etch chips. Not only could this lower production costs and time, but it could also extend the lifetime of Moores Law.
"Talking" bacteria out of causing infections.
The main cause of death among cystic-fibrosis patients, and a threat to many burn victims and AIDS patients as well, is the bacterium Pseudomonas aeruginosa. But the microbe is not a health problem until enough of the bacteria join together to form a gooey amalgamation called a “biofilm.” Almost 80 percent of bacterial infections are in biofilm form. Helen Blackwell, an assistant professor of chemistry, studies quorum sensing – the communications mechanism that tells bacteria that they have replicated enough to form a biofilm. Its easy, according to Blackwell, to synthesize the organic molecules that bacteria use to talk to each other.
Blackwell is testing a series of such messenger molecules to see if she can hijack the bacterias communications network. So far, of the hundreds of molecules she has screened, 10 seem promising. The right molecule might fight a hard-to-treat infection or induce a small, early infection to stimulate the bodys immune response. Blackwells group developed a way to speed up the reaction that produces the messenger molecules by heating it with microwaves. “We reduce a reaction sequence from about three days to about 45 minutes,” she says.
Building novel pathogen detectors.
Physicist and physician Anita Goel finds inspiration in the tiny: the proteins that inch their way along DNA, reading and copying the genes inside every cell. As a physics graduate student at Harvard University, Goel developed a theory to explain how these molecular motors work. While working on her medical degree at Harvard in 2004, she founded Nanobiosym to apply her theories to the development of nanotech devices for precisely controlling these proteins; such devices could identify viruses and bacteria in, say, a blood sample more rapidly, accurately, and cheaply than current techniques can. Her goal: a low-cost, handheld device for biodefense and biomedical applications.
Following inspiration for inventing.
Before Saul Griffith perfected his five-minute method for making custom-crafted lenses for $5, he volunteered in South America, where he once had to hand a pair of dainty granny glasses to a six-foot-tall man: they were the only pair the volunteer group had that fit the mans prescription, he recalls. And it was from kite-surfing, a sport that relies on the strength of the ropes tethering a surfer to a wind-drawn parachute, that Griffith drew the idea for smart ropes, in which embedded conductive threads reveal developing weaknesses. After pursuing such ideas en route to his doctorate at the MIT Media Lab, he cofounded Squid Labs to explore the business of inventing. Among his projects: “open source hardware,” to do for computer equipment what Linux did for operating systems.
Fabricating microarrays faster.
Microarrays are slides dotted with hundreds of thousands of different gene segments that help researchers spot particular DNA sequences – making microarrays invaluable tools for the study of genetically influenced diseases ranging from diabetes to many forms of cancer. But current methods for manufacturing microarrays are very costly and time consuming because of the dozens of printing steps they require. Materials science assistant professor Francesco Stellacci may have found a way to quickly produce microarrays for as little as $50. In his approach, a single strand of DNA “stamps” genetic information into a slide, which can then serve as a master template for the production of multiple identical arrays.