Despite recent advances in technology for upper-limb prostheses, artificial arms and hands still cannot provide users with sensory feedback, such as the “feel” of things being touched or awareness of limb position and movement. Without this feedback, even the most advanced prosthetic limbs remain numb to users, a factor that impairs the limbs’ effectiveness and their wearers’ willingness to use them. By restoring sensory functions, HAPTIX also aims to reduce or eliminate phantom limb pain, which affects about 80 percent of amputees.
Effective user control of these prosthetics has been particularly challenging, and various methods have been attempted with limited success. Transcutaneous leads that interface with nerves under the skin have been used, as have other designs with leads that sense the muscular twitching in a stump. In addition to conquering the control issues, a relatively recent goal has been to restore a sense of touch to the amputee through sensors that are part of the prosthetic limb.
“The ultimate goal for HAPTIX is to create a device that is safe, effective and reliable enough for use in everyday activities,” Doug Weber, DARPA program manager, said in a news release. “DARPA is partnering with scientists at the [U.S.] Food and Drug Administration to help develop standards for verifying safety and quantifying benefits of this new class of advanced technologies. We hope to streamline the process of validating technologies that can help our military service members and veterans who have been injured while serving our country.”
DARPA is evaluating several distinct technical approaches in the project's first phase. Those that prove successful would continue into the second phase, which would integrate selected technology components into a complete HAPTIX test system. The agency plans to initiate take-home trials of a complete, U.S. Food and Drug Administration-approved HAPTIX prosthesis system within four years.
The agency is working to develop the prosthetic limbs with research teams fromCase Western Reserve University (Cleveland, Ohio); the Cleveland Clinic; Draper Laboratory (Cambridge, Mass.); Nerves Incorporated (Dallas,Texas); Ripple LLC (Salt Lake City, Utah); University of Pittsburgh (Pennsylvania); the University of Utah; and the University of Florida.
- Implantable Myoelectric Recording Array for Control of Prostheses, awarded to Ripple LLC. Ripple’s technology is an implantable wireless device that aims to increase reliability of prosthetic limbs and create a more natural movement. Currently, surface electrodes provide slow and poorly controlled movements. Wireless interface will be achieved with the attached prosthetic, and implantation is minimally invasive.
- Multisite Intrafascicular Stimulation for Stance, awarded to Richard A. Normann, Ph.D., of the University of Utah in Salt Lake City. Normann has developed the Utah Slanted Electrode Array (USEA), which provides more uniform coverage to peripheral nerves when implanted within them. The USEA can communicate with nerve fibers and receive information from many of them at a time, then translate output to only a select few. This provides smooth and specific movements of muscles that are more natural, while generating minimal fatigue.
- Enhancing Neuroprosthesis Performance with Nerve Cuff Electrodes, awarded to Dustin Tyler, PhD at Case Western Reserve University. Tyler has designed and tested high-density electrode nerve cuffs in patients suffering from injured spinal cords. Wrapping around major nerves in the limbs, the cuffs stimulate these nerves, inducing movement in the limb, which can be used to drive prosthetics. The sensors will also be used to stimulate sensations in sensory nerves, thus providing artificial sensory input to the patient.