Research on a new kind of carbon nanotube artificial muscle for Air Force aerospace and space applications, conceived and invented, at the University of Texas at Dallas (UTD) is receiving primary financial support from the Air Force Office of Scientific Research (AFOSR).
Dr. Ray Baughman, director of the NanoTech Institute at UTD, and his team of researchers have been working on artificial muscles for more than twenty years. The current phase of his pioneering work stems from an exploratory research program supported by AFOSR program manager, Dr. B-L "Les" Lee since 2006. The team invented many new types, including electrochemical carbon nanotube and conducting polymer muscles, as well fuel-powered muscles. The latter, powered chemically by alcohol or hydrogen, operate similarly to natural muscles. But they are limited in that they cannot function at extreme temperatures and have low efficiencies for energy conversion.
The nano-based muscles, which are 30 times stronger than natural muscles are made of very thin sheets of nanotubes (1/10,000th of the diameter of a human hair) that on a weight basis are "strong as steel" in one direction and as elastic as rubber in two other directions. These properties and their deployment for giant stroke artificial muscles were described in the March 20, 2009 issue of Science.
These non-electro chemical carbon nanotube artificial muscles can 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, which would be advantageous in battlefield emergencies. Artificial muscles may also be used to actuate "smart skins," which would give Air Force aircraft the ability to change their appearances in situations of danger.
"We want to use the carbon nanotube sheets to affect the boundary layers on Air Force micro air vehicles and even larger vehicles to provide a new type of controllability and increase flight efficiency," Baughman said.
"The carbon nanotube aerogel sheets are a remarkable state of matter that show rubber elasticity, and they are lighter than air. The sheets rise in the air like smoke," said Baughman who remains amazed by their properties.
Baughman and his colleagues activate the artificial muscles by injecting a small amount of positive charge into the carbon nanotube sheets.The positive charge repulses the other positive charges within the carbon nanotube sheet.
"Natural muscles contract at about 20 percent per second, but the artificial muscles' rate can exceed 30,000% per second," he said.
Up ahead, scientists expect these latest man-made muscles to have very large response rates that as of right now are not possible.
"To use our muscles of this type to generate large forces, we must learn how to assemble hundreds of the individual sheet strip muscles to make ones having large cross-sectional areas," he said.
In addition to AFOSR, funding is being provided by the Office of Naval Research, the Strategic Partnership for Research in Nanotechnology, and the Robert A. Welch Foundation.
Maria Callier
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