Finding the right nanotubes.
Carbon nanotubes have excellent electronic properties that make them attractive for use in future high-performance computers. But a given batch of carbon nanotubes can contain as many as 80 different types, each with distinct properties. While this diversity is potentially appealing, it's also one of the major obstacles to the use of carbon nanotubes. Because it's not possible to isolate carbon nanotubes by type, nanotube-based devices have either been one-off prototypes or have relied on the average properties of bulk nanotubes. (See "Carbon Nanotube Computers.") However, a new technique based on an ultrafast centrifuge is now enabling researchers to sort nanotubes by their electronic properties, making it far easier to study them and develop new applications. (See "Nanotube Computing Breakthrough.") Another technique, in an earlier stage of development, could be even more precise. It "clones" specific nanotubes by chopping them up and then growing new nanotubes from these fragments. (See "Cloning Nanotubes.") According to one researcher, being able to isolate nanotube types is like having access to a new periodic table.

Handheld chemical and biological sensors.
Nanowires are ideal for detecting chemical weapons and even individual virus particles. That's because when such substances bind to nanowires, even in extremely low quantities, the wires' conductivity changes markedly. Researchers are moving closer to realizing such sensors by improving the speed of nanowire transistors. (See "Nanowire Transistors Faster than Silicon.") Others have developed a method for forming two different types of nanowires on the same surface to make energy-saving circuits that will rule out false positives, improving the accuracy of nanowire sensors. (See "Nanowire Computing Made Practical.") Hundreds of nanowire transistor-based circuits could easily be incorporated into a handheld device, allowing instant detection of hundreds of important chemical and biological materials.

Mix-and-match electronic circuits.
Although they offer advantages for particular applications in computing, nanoscale structures such as nanotubes and nanowires are unlikely to completely replace conventional transistors, at least in the near future. (See "The Future of Nanoelectronics.") Indeed, it would be ideal to combine various types of structures in one device, capitalizing on the strengths of each. But this isn't easy, since, for example, the temperatures required for processing one material or structure can damage others. Researchers at the University of Illinois, Urbana-Champaign, have developed an inexpensive way to integrate all sorts of materials and structures onto the same surface--and the surface can even be a flexible polymer. Different types of materials can be laid down side by side or on top of each other in successive layers. This could lead to cheaper, more compact night vision for soldiers and even flexible displays that are scaled-down versions of the bright and vivid LED-based displays found in sports arenas. (See "Making Nanoelectronics for Displays.")