Gallery: Bionic Arms Gain Power, Dexterity, Sensitivity

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Prosthetic legs have gotten an image boost recently, thanks to the high-performance carbon-fiber springs worn by the likes of Oscar Pistorius and Aimee Mullins. But prosthetic arms still call to mind stiff, heavy chunks of plastic — barely one step up from Captain Hook’s creepy iron claw.

“Prosthetic legs are in the 21st century,” Dean Kamen recently told the trade publication IEEE Spectrum. “With prosthetic arms, we?re in the Flintstones.” Kamen, who invented the Segway, has been working on creating an advanced artificial limb.

The human hand is difficult to replicate. It’s an instrument that can squeeze a lime as effectively as it can hold a delicate lightbulb. The hand is not just about mechanical movement: Its sense of touch offers important feedback to the brain about the texture and nature of the object.

Conventional prosthetic arms are little more than sophisticated hooks that offer very little freedom of movement. They offer just three degrees of freedom: opening and closing the hand, rotating the hand inwards and outwards, and bending and extending the elbow. And going through those motions requires concentration and a level of skill that can be rather exhausting.

Advanced prosthetic arms promise a lot more. While not a perfect replacement for a human limb, the idea is to offer almost the same level of flexibility, dexterity and feedback that the hand can.

An extraordinary project from the Defense Advanced Research Projects Agency promises to make it happen. Darpa’s $100 million Revolutionizing Prosthetics 2009 Program aims to create a thought-controlled functional arm within this decade. The project is a collaborative effort with more than 30 organizations including labs, universities and private companies.

The Darpa program has created two kinds of prototypes. The first is a sophisticated prosthetic arm that can be controlled naturally, provide sensory feedback and allow for eight degrees of freedom. The second, more ambitious, venture aims to offer natural movement and a range of motion similar to a real arm.

Photo: iLimb from Touch Bionics