Baughman and his colleagues have already made carbon-nanotube-based muscles that are 100 times stronger than natural muscle and more flexible than rubber. The researchers created the yarn by first growing forests of carbon nanotubes, each about 400 micrometers tall and 12 nanometers wide. They then spun them together into long bundles that are less than 10 micrometers thick.
To create the twisting motion, the yarn is connected to an electrode and immersed in an electrolyte. Ions from the electrolyte enter the yarn, which causes it to first swell and then contract and rotate along its length.
Boris Yakobson, a professor of chemistry, materials science, and mechanical engineering at Rice University, says he is curious about the energy efficiency of the system, and would have liked to see some measurements or even estimates in the paper. He says with any such motor, some important characteristics are “how much electrical energy is put in, and how much mechanical work can be produced in rotation. In any case, this is fascinating nanoengineering.”