198. For decades, the size of silicon-based transistors has decreased steadily while their performance has improved. As the devices approach their physical limits, though, researchers have started looking to less conventional structures and materials. Single-walled carbon nanotubes are one prominent candidate -- already researchers have built carbon nanotube transistors that show promising performance. According to estimates, carbon nanotubes have the potential to produce transistors that run 10 times faster than even anticipated future generations of silicon-based devices, while at the same time using less power.

199. Importance: Could help make large-scale integrated circuits built out of carbon nanotubes possible, leading to ultrafast, low-power processors. The need to power IT equipment becomes less of a factor in planning military operations.

200. Status: Researchers at have overcome an important obstacle to building computers based on carbon nanotubes, by developing a way to selectively arrange transistors that were made using the carbon molecules.

201. Most flexible electronics, such as those used in e-paper and roll-up displays for mobile devices, rely on transistors made of either organic polymers, printed directly on a plastic substrate, or amorphous, or noncrystalline, silicon. However, transistors made of these materials can't perform at the gigahertz speeds needed for complex circuitry or antennas.

202. People have for some time been able to make slow flexible electronics, but the speed of the transistors has been limited. The next step has been to make the transistors out of high-quality, single-crystal silicon instead of organic polymers and amorphous silicon because electrons simply move faster in single-crystal silicon.

203. Importance: This technology opens possibilities to new flexible electronics that can be implemented in a wide variety of military applications. Imagine you are an infantry soldier and you look to your wrist computer to get your bearings, known positions of friend and foe and even a weather report. Flexible electronics has the potential to revolutionize the way in which information is disseminated on the battlefield.

204. Status: Researchers have made ultra thin silicon transistors that operate more than 50 times faster than previous flexible-silicon devices. The advance could help make possible flexible high-end electronics that would be useful in a variety of applications, from computers to communication.

205. Optical fibers can quickly transmit huge amounts of data. But the technology for sorting and sending photons lags far behind the microelectronics that generates and process the data, putting a crimp on bandwidths. In the past few years, scientists and engineers have made great strides in miniaturizing photonic devices and integrating them onto a single chip. Such advances allow for cheaper manufacturing, smaller sizes, and higher performance. Along the way they've developed techniques for working with materials common to the semiconductor industry, which is a step toward integrating photonics and electronics on the same chip. And these researchers have made structures with phenomenal precision, in some cases down to distances smaller than those that separate atoms.

206. Even with these successes, however, a major obstacle remained. Light delivered via cylindrical fiber optics breaks into different polarizations, or orientations of light waves. In devices at the microscale, the outputs change depending on if the waves are oriented vertically or horizontally so they're suited to processing only certain polarizations, which can lead to weakened signals. If researchers are limited to using horizontally polarized light, for example, they end up throwing away vertically polarized light and lose half the signal strength. That's a problem particularly when sending signals over long distances, such as between continents.

207. One approach to this problem is to run light through more than one device, each specifically designed to process one polarization. Researchers at MIT's Research Laboratory of Electronics took a different approach. Rather than building separate devices for different light polarizations, they invented a device for converting vertically polarized light into horizontally polarized light. First, the device splits light into its horizontally and vertically polarized components, directing these into separate channels. Then it gradually rotates the vertically polarized light to make it horizontal. At this point, the light in both channels has the same polarization. This makes it possible to use identical devices to process that light. As a result, all of the light is processed in the same way, allowing clear, strong signals.

208. The current advance pertains only to those photonic applications that involve light with multiple polarizations and those communications applications that involve fiber optics. There hasn't been much economic pressure in the past couple of years to develop technology for these applications because of a glut in bandwidth, but now communications demands are increasing again.

209. Importance: Paves the way to cheaper, more complex, and higher-performance optical networks. When you integrate things like this, the complexity and the performance of the kinds of filtering we can do are a little more advanced than the methods that are used today. For example, sensor assemblies using photonic components are immune to electromagnetic interference and electrical component failure in adverse environments.

210. Status: Researchers at MIT's Research Laboratory of Electronics report in the current issue of Nature Photonics that they have developed a method for overcoming a fundamental problem in using photonics in communications.

211. Researchers have fabricated high performance, transparent thin-film transistors (TFTs) using a low-cost, low-temperature method. They use indium oxide as both a semiconductor and a conductor, combining the inorganic material with organic insulators on top of a transparent substrate. The resulting transistors perform nearly as well as the much more expensive polysilicon transistors used to control pixels in high-end TVs and computer monitors.

212. On glass that's been coated with a transparent electrode, the researchers deposit the organic insulating materials, which form a multilayered lattice. To deposit the indium oxide, the researchers use a standard technique called ion-assisted deposition, in which an ion beam controls the crystallization and adhesion of the oxide. Changing the oxygen pressure during the process varies the conductivity of the indium oxide, which can thus be used as a semiconductor in one part of the device and as a conductor in other parts.

213. Importance: The new TFTs could replace the opaque transistors used to control pixels in digital displays. Because the low-temperature method can deposit transistors on flexible plastics, it could lead to see-through displays affixed to curved surfaces such as windshields and helmet visors. The method is also cheap enough, and easy enough to adapt for large-scale manufacturing, that it could make such displays affordable. Imagine a vehicle windshield that displays a map to your destination, military goggles with targets and instructions displayed right before a soldier's eyes.

214. Status: Negotiations for licensing the technology have begun. Prototype displays could be ready within 18 months. The researchers hope to improve the performance of the transistors so that they could serve as processors or memory cells.