Prometheus 6

The video of all this is pretty cool. Because the whole thing is in Flash I can't directly link it. You have to look for this little "Story Map" tag in the upper left sector of the screen. Click that and you'll get a little drop down navigation aid. 

Unconventional power source could revolutionize the design of prosthetic limbs
By David F. Salisbury
Published: August 20, 2007 

Combine a mechanical arm with a miniature rocket motor:  The result is a prosthetic device that is the closest thing yet to a bionic arm.

A prototype of this radical design has been successfully developed and tested by a team of mechanical engineers at Vanderbilt University as part of a $30 million federal program to develop advanced prosthetic devices.

“Our design does not have superhuman strength or capability, but it is closer in terms of function and power to a human arm than any previous prosthetic device that is self-powered and weighs about the same as a natural arm,” says Michael Goldfarb, the professor of mechanical engineering who is leading the effort.

The prototype can lift (curl) about 20 to 25 pounds – three to four times more than current commercial arms – and can do so three to four times faster. “That means it has about 10 times as much power as other arms despite the fact that the design hasn’t been optimized yet for strength or power,” Goldfarb says.

The mechanical arm also functions more naturally than previous models. Conventional prosthetic arms have only two joints, the elbow and the claw. By comparison, the prototype’s wrist twists and bends, and its fingers and thumb open and close independently.

The Vanderbilt arm is the most unconventional of three prosthetic arms under development by a Defense Advanced Research Project Agency (DARPA) program. The other two are being designed by researchers at the Advanced Physics Laboratory at Johns Hopkins University in Baltimore, who head the program. Those arms are powered by batteries and electric motors. The program is also supporting teams of neuroscientists at the University of Utah, California Institute of Technology and the Rehabilitation Institute of Chicago who are developing advanced methods for controlling the arms by connecting them to nerves in the users’ bodies or brains.