Alex Smith was He was 11 years aged when he lost his right arm in 2003. A drunk driver driving a boat collided with the family’s vessel on Lake Austin, causing him to fall overboard. He hit the propeller and his arm was severed in the water.
A year later, he received a myoelectric arm, a type of prosthesis powered by electrical signals in the muscles of his residual limb. But Smith barely used it because it was “very, very slow” and had restricted range of motion. He could open and close his hand, but there wasn’t much else he could do. He tried other robotic arms over the years, but they had similar problems.
“They’re just not super functional,” he says. “There is a huge delay between when a function is performed and the prosthetic actually does that action. In my everyday life, I simply found other ways of doing things more quickly.”
Recently, he’s been trying out a up-to-date system from Austin-based startup Phantom Neuro that could provide more realistic control of prosthetic limbs. The company is building a lean, elastic muscle implant that will allow amputees a wider, more natural range of motion just by thinking about the gestures they want to make.
“Not many people use robotic limbs, and that’s mainly because the control system is terrible,” says Connor Glass, CEO and co-founder of Phantom Neuro.
Data shared exclusively with WIRED shows that 10 participants in Phantom’s study used a portable version of the company’s sensors to control a robotic arm already available on the market, achieving an average accuracy of 93.8% across 11 hand and wrist gestures. Smith was one of the participants, and the other nine were able-bodied volunteers, which is common in early prosthetics research. The success of this study paves the way for testing implantable Phantom sensors in the future.
Current myoelectric prostheses, like the ones Smith tried, read electrical impulses from surface electrodes placed on the amputated stump. Most robotic prostheses have two electrodes or recording channels. When a person bends their arm, the arm muscles contract. These muscle spasms still occur in upper limb amputees when they are flexed. The electrodes receive electrical signals from contractions, interpret them and initiate movements of the prosthesis. However, surface electrodes do not always capture stable signals because they can slip and move, reducing their accuracy in real environments.