The sensors and chips for the Smart Integrated Lower Limb (SILL) project will be developed by Sandia National Laboratories, funded by the U.S. Department of Energy (DOE). Materials work and testing is performed by the Russian nuclear weapons laboratory Chelyabinsk 70, whereas the technical requirements for the limb will be set by the Seattle Orthopedic Group (SOGI). SILL is the third of three projects on prosthetics, that is undertaken with the Russian nuclear scientists. Project manager Diane Hurtado takes over from the recently retired Sandian, Mort Lieberman, who originated the prosthetics programme, starting with a prosthetic foot which has now reached the stage of being worn by soldiers who lost a foot in Chechnya. In 1999, a project was initiated to create an artificial knee.
The leg, which is currently being developed in the SILL project, is intended to simulate a human gait whether on uphill, downhill, or even irregular terrain. Therefore, a microprocessor-controlled module, that is 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. In addition, the leg socket will adjust to the changing diameter of an amputated stump over the course of a day, reducing sores, improving comfort, and increasing time of use. The advance should enable otherwise competent amputated people to maintain active lives rather than be confined to wheelchairs or rest homes.
"This is about making a leg which is more like a missing limb than a collection of components ever can be", stated the SILL project manager Diane Hurtado. "This limb will have a digital control system to make it smart." Ivan Sabel, president of Hangar, of which SOGI is a division, added: "This is taking an industry which has gone in thirty years from plastic to carbon fibres, to the next generation." Amputees need a way to walk without falling down, that is fully independent of the kind of terrain, according to Sandia researcher Dave Kozlowski, who has designed robotic architectures for surgical operating rooms. "The majority of lower-limb prosthetic devices are based upon 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, which will enable a more normal and efficient walking gait", stated Dr. Kozlowski. A proper limb motion will return energy to the wearer instead of draining it, to his conviction. "One challenge to be addressed is designing a power source light enough for an amputee to feel comfortable carrying it", he added.
Sandia researcher Diane Hurtado inspects older prosthetic devices lent by SOGI to Sandia.
The synthetic lower limbs are expected to help researchers generate ideas for the next generation of prosthetics.
Photo courtesy of Sandia National Laboratories.
Sandia researcher Mark Vaughn, who will equally participate in the project, explained that another objective is to make a self-adjusting prosthetic socket which will prevent pressure sores caused by the device rubbing against the residual limb. The accurately fitting socket will change shape to match the swelling of the amputee's contact limb over the course of a day. This third combined American-Russian effort is being funded by the DOE's Initiatives for Proliferation Prevention, which puts scientists who formerly have been involved in the nuclear arms race to work on humanitarian projects. DOE is awarding the current project with $1.5 million over two years. In turn, SOGI is expected to put up a matching amount in money, goods, and services.