This is a scanning electron micrograph image of a 3.8-micron diameter carbon nanotube yarn that functions as a torsional muscle when filled with an ionically conducting liquid and electrochemically charged. The angle indicates the deviation between nanotube orientation and yarn direction for this helical yarn. (Image courtesy of the University of Texas at Dallas)
New artificial muscles that twist like the trunk of an elephant, but provide a thousand times higher rotation per length, were announced on Oct. 13 for a publication in Science magazine by a team of researchers from The University of Texas at Dallas, The University of Wollongong in Australia, The University of British Columbia in Canada, and Hanyang University in Korea.
These muscles, based on carbon nanotubes yarns, accelerate a 2000 times heavier paddle up to 590 revolutions per minute in 1.2 seconds, and then reverse this rotation when the applied voltage is changed. The demonstrated rotation of 250 per millimeter of muscle length is over a thousand times that of previous artificial muscles, which are based on ferroelectrics, shape memory alloys, or conducting organic polymers. The output power per yarn weight is comparable to that for large electric motors, and the weight-normalized performance of these conventional electric motors severely degrades when they are downsized to millimeter scale.
