ASU’s progressing research with a prosthetic ankle will allow many amputees the opportunity to walk and eventually jog and run gracefully.

SPARKy, a spring ankle with regenerative kinetics, is the only technology of its specific type that can help amputees navigate with ease, the project’s principal investigator said.

The technology is unique because the ankle device can rotate, uses regenerative kinetics and is not passive like other models.

Thomas Sugar, an associate engineering professor at the Polytechnic campus who specializes in robotics, started the research in January 2007. The project is expected to be finished this summer.

The concept of regenerative kinetics is storing and releasing of energy while walking with the ankle device, Sugar said.

“As your leg rolls over the ankle, your leg needs to be slowed down or braked,” he said. “We store that energy in the springs and then we use that energy to propel you forward.”

Sugar compared the process to what happens in electric or hybrid cars when they stop and use stored energy to start again with less gasoline.

“We just do that by storing energy in a spring and using that energy, along with a motor … to help you to … move the ankle up and down,” Sugar said.

There are three basic types of prosthetic devices: motors and springs, high-pressure oil and carbon fiber feet.

Sugar said the carbon fiber feet are passive in their springs, which means the ankle doesn’t have a joint that can rotate, though they store and release energy like his device.

Right now, most people are using that type of device, he said.

“By not rotating back and forth, it doesn’t allow you to have a nice, smooth motion,” Sugar said. “They don’t put energy into walking, and you need energy to walk.”

Another motorized spring device is in development by Hugh Herr at Massachusetts Institute of Technology.

“It’s similar, but the … way we actually control the ankle is different,” Sugar said.

There are microprocessor prosthetic knees on the market, but no bionic ankles that have the advanced capabilities Sugar’s model has, he said.

The research project received $680,000 for three years from the U.S. Department of Defense, Sugar said, and the funding ends in August.

The Human Machine Integration Laboratory at ASU, which Sugar advises, worked with Arise Prosthetics in Phoenix on recruiting and other aspects of the research, as well as a robotics company for some materials.

In its first year, the research focused on participants using the device to walk on a treadmill, he said.

In 2008 and 2009, the electronic parts of the device were minimized so it would be less bulky. The device was tested by walking on ground, slopes and stairs.

“In this third phase, we’re supposed to do some jogging on a treadmill,” Sugar said. “We’re working on designing … for jogging, the device needs to be much stronger.”

He added that the device needs to be more powerful for jogging and the electronics must be further reduced.

Lt. Col. Joseph Hitt, an assistant professor of civil and mechanical engineering at the U.S. Military Academy at West Point, started working on the research in 2007 as a doctoral student at ASU and still does research with Sugar. He helped design the first model and test it.

“I was able to come up with the math to allow us to design the most efficient system possible, which allows us to downsize how big the batteries are,” Hitt said. “This project was sponsored by the military with the initial effort being helping our wounded warriors.”

George Wolf, an associate professor of chemistry and biochemistry, started working on the research as a participant about a year ago, he said in an e-mail.

“The work has a real possibility of advancing the field of prosthetics and helping amputees, like myself, live a fully normal and active lifestyle,” Wolf said, adding that he decided to join the research so he can help others and give specialized information.

“As a scientist and an amputee guinea pig I feel that I can give a unique perspective on what works and what doesn’t,” he said.

The prosthetic devices he uses now are not as efficient as SPARKy, he said, which feels like his natural leg because it is a passive device.

“In a passive leg I have to enlist the muscles of my upper leg and hip to supply the missing power,” he said.

Wolf said he plans on continuing research with Sugar to create a lighter and improved version of the device.

“We need all these advancements in a leg that is robust enough to handle rain and mud and everything else we humans put our bodies through,” he said.

Reach the reporter at reweaver@asu.edu