AFRL-funded Research Leads to Super-Strong Nano-based Muscles

  • Published
  • By Robert White
  • Office of Scientific Research
ARLINGTON, Virginia --  Funding by the Air Force Research Laboratory is supporting a University of Texas/Dallas research team's pioneering work in artificial muscle types, including electrochemical carbon nanotube and conducting polymer muscles, as well fuel-powered muscles.

This pioneering work stems from an exploratory research program supported by AFRL program manager Dr. Byung-Lip "Les" Lee since 2005, whereby the team invented many new muscle types. One of those types--fuel-powered muscles--are powered chemically by alcohol or hydrogen and operate similarly to natural muscles, but cannot function at extreme temperatures and have low efficiencies for energy conversion. The nano-based muscles, 30 times stronger than natural muscles, are made of very thin sheets of nanotubes (1/10,000th the diameter of a human hair). On a weight basis, they are as strong as steel in one direction and as elastic as rubber in two other directions. These artificial muscles can also operate at extreme temperatures, which makes them especially attractive for space applications. They are also being viewed as a means for endowing soldiers with super-human strength through the use of exoskeletons.

Artificial muscles may also be used to actuate "smart skins," which would give Air Force aircraft the ability to change their appearance with the use of carbon nanotube sheets to affect the boundary layers on Air Force micro air vehicles, or larger vehicles, providing a new type of controllability and increased flight efficiency.

The most recent research by this team has resulted in new artificial muscles made from nanotech yarns infused with paraffin wax that can lift more than 100,000 times their own weight and generate 85 times more mechanical power during contraction than the same size natural muscle. The new artificial muscles are made by infiltrating a volume-changing "guest," such as the paraffin wax used for candles, into twisted yarn made of carbon nanotubes. Heating the wax-filled yarn causes the wax to expand, the yarn volume to increase, and the yarn length to contract. 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.