Sandia LabNews

Agreement signed to create a 'smart' leg

Prosthetic limb to be controlled by microchip; Labs, Russians, industry will collaborate

Over the past two years, Sandia has joined forces with the Russian nuclear lab Chelyabinsk 70 and American private industry to create a superior prosthetic foot and also a better prosthetic knee.

On Sept 26, 2000, still working with the former "enemy" Russian lab, Sandia signed a two-year cooperative research and development agreement (CRADA) with the Seattle Orthopedic Group, Inc. (SOGI) to create an entire, "smart," artificial leg.

The signing ceremony took place in the auditorium of Bldg. 895, the Robotics Manufacturing, Science, and Engineering Laboratory (RMSEL). Sensors and chips will be developed by Sandia. Materials work and testing will be performed by the Russians. Technical requirements for the limb will be set by SOGI.

"This is about making a leg that is more like a missing limb than a collection of components ever can be," says Diane Hurtado (15222) of the Smart Integrated Lower Limb (SILL) project team. "This limb will have a digital control system to make it smart."

Expected to be on the market in two years, the prosthesis should aid the tens of thousands of Americans yearly whose lower limbs must be amputated due to diabetes, auto accidents, and other causes. The advance should enable otherwise competent amputees to maintain active lives rather than be confined to wheelchairs or rest homes. 

To walk without falling

The leg is intended to simulate a human gait whether on uphill, downhill, or even irregular terrain. To do so, a microprocessor-controlled module implanted in the leg will respond to sensor input from multiple sources. The microprocessor will control hydraulic joints and piezoelectric motors that power the ankle, knee, and socket.

It is also intended to be comfortable to wear.

"What amputees are clamoring for is a way to walk without falling down, independent of terrain," says Sandia researcher Dave Kozlowski (15272), who has designed robotic architectures for surgical operating rooms. "The majority of lower-limb prosthetic devices are based on passive technologies that require far more energy for amputees to cover the same distance as non-amputees." In passive technologies, as the thigh moves forward, inertia opens the knee joint, the artificial shin swings forward, and, when the entire structure locks, the wearer can pass his or her weight over it. The feet are usually not ‘smart’ in adjusting to terrain.

"We intend to develop a much more efficient device, with sensors placed at strategic points along foot and leg, that will enable a more normal and efficient walking gait," says Dave. A proper limb motion will return energy to the wearer instead of draining it, he says.

One challenge to be addressed is development of a power source that is light enough for an amputee to feel comfortable carrying it, he says.

Comfort for wearers

Sandia researcher Mark Vaughn (15252), who also will participate in the project, says another goal is to make a self-adjusting prosthetic socket that will prevent pressure sores caused by the device rubbing against the residual limb. The device will change shape to match the residual limb’s swelling over the course of a day.

"The funding gives us a couple of man-centuries of Russians to throw at the problem, and it’s right down their alley," says Mark. "They’re mechanical guys. We should get quite a bit of accommodation." Approximately 120 Russian scientists who used to design nuclear weapons are expected to participate in the project, funded by DOE’s Initiatives for Proliferation Prevention.

Says Sandia manager for international initiatives Bob Huelskamp (5353), "Sandia generally thinks it’s impressive if, say, five of its scientists leave to start an entrepreneurial enterprise. This prosthetics project means that, at a minimum, dozens, and if the project takes off, triple figures of Russians formerly in the weapons-of-mass-destruction business are moving out of that into a humanitarianly useful, and hopefully commercially successful, business venture."

Says Olen Thompson (1320), "This project got its start through the integrated efforts of the principal investigators, CRADA specialists, licensing specialists, patent attorneys, and the DOE/AL Technology Partnership Office. They had many barriers to overcome but they stayed with it because they believed in the project’s importance." DOE is funding the current effort with $1.5 million over two years. SOGI is expected to put up a matching amount in money, goods, and services.

Prosthetics: The next generation

Said Ivan Sabel, president of Hangar, of which SOGI is a division, says, "This is taking us — an industry that has gone in 30 years from plastic to carbon fibers — to the next generation." Diane takes over project management of Sandia’s prosthetics program from retired Sandian Mort Lieberman, who originated it.

Mort, who spoke at the CRADA signing about the change in direction at the Russian nuclear lab and, to some extent, at Sandia initiated by his work and others, quoted anthropologist Margaret Mead: "Never doubt that a small group of concerned citizens can change the world."

Last modified: Oct. 9, 2000