Ready for human testing: DARPA's versatile prosthetic limb, controlled by user’s thoughtsS

The Modular Prosthetic Limb allows 22 degrees of motion, independent movement of the fingers, weighs as much as a human arm, and responds to the user's thoughts. So how is it different from a real arm? It really isn't.

Developed by the Applied Physics Laboratory at Johns Hopkins University, the limb has nearly the same range of motion as a natural limb. The Defense Advanced Researched Projects Agency, or DARPA, has just awarded its designers $35.6 million to test the device on human subjects.

Program manager Michael McLoughlin explains what they hope to achieve in this next stage:

"We've developed the enabling technologies to create upper-extremity prosthetics that are more natural in appearance and use, a truly revolutionary advancement in prosthetics. Now, in Phase 3, we are ready to test it with humans to demonstrate that the system can be operated with a patient's thoughts and that it can provide that patient with sensory feedback, restoring the sensation of touch."

The team is working with researchers at the University of Pittsburgh and California Institute of Technology to develop the neural technology needed to make this goal a reality. They are developing better algorithms to maximize the dexterity of the new limbs when responding to commands from the brain, as well as conducting tests to make sure their neural interfaces can be manipulated safely. These interfaces rely on micro-arrays that both record brain signals and stimulate the brain in turn.

Their first tests will focus on five patients with high spinal cord injuries. As McLoughin explains:

Initially, we have targeted the quadriplegic patient population because they have the most to gain. Unlike most amputee patients who have other options in terms of care and independence, these patients are totally dependent on others for most things. There is no alternative. Their lives will be truly transformed by this advancement."

And this is just the start of refining the technology. A team at the University of Chicago is working on how to stimulate the brain so that it can sense pressure and touch from the limb, while researchers at the University of Utah are focused on refining the electrodes that will allow patients to control the arm with their minds.

[The Johns Hopkins University Applied Physics Laboratory]