"Because of their simplicity and high performance, 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 said.
Muscle contraction also called actuation can be ultrafast, occurring in 25-thousandths of a second. Including times for both actuation and reversal of actuation, the researchers demonstrated a contractile power density of 4.2 kW/kg, which is four times the power-to-weight ratio of common internal combustion engines.
To achieve these results, the guest-filled carbon nanotube muscles were highly twisted to produce coiling, as with the coiling seen of a rubber band of a rubber-band-powered model airplane.
When free to rotate, a wax-filled yarn untwists as it is heated electrically or by a pulse of light. This rotation reverses when heating is stopped and the yarn cools. Such torsional action of the yarn can rotate an attached paddle to an average speed of 11,500 revolutions per minute for more than 2 million reversible cycles. Pound-per-pound, the generated torque is slightly higher than obtained for large electric motors, Baughman said.
Because the yarn muscles can be twisted together and are able to be woven, sewn, braided and knotted, they might eventually be deployed in a variety of self-powered intelligent materials and textiles. For example, changes in environmental temperature or the presence of chemical agents can change guest volume; such actuation could change textile porosity to provide thermal comfort or chemical protection. Such yarn muscles also might be used to regulate a flow valve in response to detected chemicals, or adjust window blind opening in response to ambient temperature.
Even without the addition of a guest material, the co-authors found
|Contact: Amanda Siegfried|
University of Texas at Dallas