Alex Smith was He was 11 when he lost his right arm in 2003. A drunk driver operating a boat collided with his family’s boat on Lake Austin, sending it overboard. He hit a propeller and his arm was cut off in the water.
A year later, he got 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 a limited range of motion. He could open and close his hand, but not do much else. 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 performing a function and then the prosthesis actually doing it. In my daily life, it became faster to discover other ways of doing things.”
Recently, he’s been testing a new system from Austin-based startup Phantom Neuro that has the potential to provide more realistic control of prosthetics. The company is building a thin, flexible muscle implant to 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 largely due to how horrible the control system is,” says Connor Glass, CEO and co-founder of Phantom Neuro.
In data shared exclusively with WIRED, 10 participants in a study conducted by Phantom used a wearable version of the company’s sensors to control a robotic arm already on the market, achieving an average accuracy of 93.8 percent across 11 gestures. of hands and wrists. Smith was one of the participants, while the other nine were healthy volunteers, which is common in early prosthetic studies. The success of this study paves the way for testing Phantom’s implantable sensors in the future.
Current myoelectric prostheses, like those Smith has tested, read electrical impulses from surface electrodes on the amputated stump. Most robotic prostheses have two electrodes or recording channels. When a person flexes their hand, the arm muscles contract. Those muscle contractions still occur in an amputated upper limb when flexed. The electrodes capture electrical signals from these contractions, interpret them and initiate movements in the prosthesis. But surface electrodes don’t always capture stable signals because they can slip and move, decreasing their accuracy in a real-world environment.