Talk about a power suit. Researchers have now created the toughest fibers ever--and they conduct electricity to boot. Such threads, made of carbon nanotubes, could revolutionize military garb by serving as both a bulletproof barrier and an electric textile that powers sensors, electronics, and communications gear.
Researchers have dreamed of making fabrics from carbon nanotubes ever since the tiny all-carbon cylinders were discovered in 1991. The strong bonds between adjacent carbon atoms make individual nanotubes one of the toughest materials known. But coaxing individual nanotubes to wrap into fibers has proven challenging. Three years ago, French researchers made headway by mixing nanotubes with a polymer called polyvinyl alcohol (PVA) and water. The spaghetti-like PVA strands wrapped around the nanotubes and helped hold them together. But when the team washed off the PVA, the nanotube fibers were only about 20 centimeters long.
Now, a group led by chemist Ray Baughman at the University of Texas, Dallas, has modified the French team's approach with impressive results. Most importantly, Baughman's group didn't try to remove the PVA from their nanotube mixture. And they also modified the fiber drawing process, sending the gel into a pipe spinning like an axle, which helps the fiber components coalesce. The result was striking: fibers hundreds of meters long that are four times tougher than spider silk, and 17 times tougher than Kevlar used in bulletproof vests. The fibers also have twice the stiffness and strength and 20 times the toughness of the same weight of steel wire, the team reports in the 12 June issue of Nature.
When Baughman's group connected twisted pairs of the fibers to a battery, they created an electric potential between the two strands, turning them into a supercapacitor, a device capable of storing electric charge. Baughman's team then wove their supercapacitor fibers with more traditional fibers to make a prototype electronic textile patch, which if hooked to a power source could help power electronic devices in the fabric.
There will doubtlessly be plenty of worthy applications for high-strength, electronically active fibers, says Wade Adams, a nanotechnology expert at Rice University in Houston. But he says the most impressive part of the new work is the fibers' strength. "Getting that kind of toughness is pretty cool." Don't expect to suit up anytime soon, though. Single-shelled carbon nanotubes--the type in the new threads--currently cost $350 a gram. That would make a 1-kilogram nanofiber suit cost a cool $350,000.