Individual carbon nanotubes are prized for their strength and stiffness, and scientists have been thinking that those properties might translate into high-performance fibers made from the material. In 2004, Alan H. Windle and coworkers at the University of Cambridge reported the fabrication of such fibers using a one-step process that employs a rotating rod to mechanically draw the fibers from a nanotube aerogel. Windle's group has now characterized those fibers and found that their strength, stiffness, and toughness are roughly twice those of DuPont's Kevlar aramid fiber, one of the toughest materials known (Science, DOI: 10.1126/science.1147635). The fibers are primarily composed of double-walled carbon nanotubes with a diameter of 4-10 nm. This relatively large diameter causes the tubes to collapse upon themselves, Windle explains, thereby maximizing the contact area between tubes. Nanotubes in the fibers measure approximately 1 mm in length. Windle notes that this high aspect ratio gives the tubes good mechanical and stress transfer properties. Next, Windle's group hopes to scale up the process for commercial production.