Nanotube Yarns With Muscle

Materials scientists are known to spin a yarn or two—such as the one about the thread that could lift 100,000 times its own weight. But in this case the yarn is true, and it’s literally a yarn. Researchers led by Ray H. Baughman of the University of Texas, Dallas, have created multiwalled-carbon-nanotube-based yarns that act like muscles, capable of lifting heavy loads (Science, DOI: 10.1126/science.1226762). The key to the lifting action is that the researchers replaced liquid electrolytes that typically surround such yarns with a solid filler material, such as wax. By using electricity to melt the wax, the yarn twists and generates motion that can lift an object. Other fillers make the yarn twist via chemical absorption or illumination. By attaching the yarn to a paddle, the team also created a rotor that spins at an average of 11,500 rpm for more than 2 million reversible cycles. They even used the yarns to create an electrically activated catapult. “These yarn muscles could be used for such diverse applications as robots, catheters for minimally invasive surgery, micromotors, mixers for microfluidic circuits, tunable optical systems, microvalves, positioners, and even toys,” Baughman says.