5. Turn It Up!
The next application could make for a noisier world: Chinese researchers have found a way to make flexible, paper-thin loudspeakers out of nanotube sheets. The scientists say the technology could be used to add an auditory dimension to anything from clothing to magazines—and to prove their point, they put one on a waving flag.
The nanospeakers don't generate sound like conventional speakers, which make noise by vibrating the surrounding air molecules. Instead, they harness a phenomenon called the thermoacoustic effect, which is how lightning produces thunder. When an electric current runs through the nanotube sheets, they heat and expand the air near them, creating sound waves.
4. Taking Lessons from the Gecko
Real-world Spidermen could one day scamper up walls thanks to an adhesive made of carbon nanotubes. The substance mimics the design of gecko feet, which are covered in millions of tiny hairs that each end in a profusion of spatula-shaped tips. The lizards can defy gravity and walk up sheer surfaces because when those tiny tips are close to a surface, they induce a strong attractive force that operates on the atomic scale, known as the van der Waals force.
The nanotech version of this system is a glue that is ten times stickier than the gecko's feet. Researchers made arrays of vertically aligned nanotubes that were topped with shorter nanotube bits, like branching treetops. The adhesive worked on a variety of surfaces, including slick glass and rough sandpaper, but its hold could easily be broken by those who knew the trick. Just like a gecko lifting its foot away from the wall, researchers pulled the glue pad away at a 90-degree angle so that only the tips of the branching nanotube bits were touching the surface, and it easily came away.
3. Flexible, Bendable Electronics
Imagine a computer screen that could be bent, folded in half, and even crumpled like a sheet of newspaper, without affecting its function in the slightest. Researchers at the University of Tokyo took a step in that direction in May when they constructed a display made of organic light-emitting diodes (OLEDs) paired with a rubbery, nanotube-based conductor.
The organic compounds in an OLED system emit light when an electric current is passed through them, and they need no backlight, making them thinner than traditional displays. As nanotubes are natural semiconductors, they channel the electricity to the organic compounds. Researchers can envision enough technological applications to fill a World's Fair, including everything from food packages with interactive displays to artificial skin for robots and coatings for airplanes that would check the craft for wear and tear.
Low-cost, large-scale fabrication could be around the corner: The researchers used a cheap industrial printing process to deposit the nanotubes on a rubbery surface.
2. Space Elevator, Going Up
Carbon nanotubes are renowned for their superior strength, and in March researchers from the University of Texas manipulated that property to create a material that is simultaneously strong, stretchy, and nearly as light as air. The researchers made an aerogel (a low-density solid) out of nanotubes, and found that in was as strong as steel. Meanwhile, applying voltage to the material made it stretchier than rubber.
What possible uses could the world find for such a material? One idea is to fashion nanotube ropes to act as cables for a space elevator, which could lift astronauts, cargo, or even tourists into orbit. The 62,000-mile-long cables would have to be strong and flexible so they wouldn't break when buffeted by atmospheric storms and space debris, but light enough so they wouldn't collapse under their own weight.
1. Tumor Blitz
The tiny tubes could even end up as must-haves in cancer hospitals one day. In a recent study, researchers injected carbon nanotubes into kidney tumors in mice, and then directed a near-infrared laser at the tumors. The tubes responded to the laser blast by vibrating, which created enough heat to kill surrounding tumor cells.
In the group that received the highest dose of nanotubes followed by a 30-second laser treatment, the tumors shrank and completely disappeared in 80 percent of the mice. The procedure didn't appear to damage the animals’ internal organs, and left only a slight burn on the skin. But researchers haven't yet proven that nanotubes are safe and non-toxic, and say that much more research must be done before such procedures are ready to be tested in humans.