Muscle Implants Could Allow Mind-Controlled Prosthetics—No Brain Surgery Required

Alex Smith is In 2003, at age 11, he lost his right arm. He hit the propeller and his arm was severed in the water.

A year later, he received Myoelectric arma prosthetic limb powered by electrical signals in the muscles of the residual limb. But Smith rarely uses it because it’s “very, very slow” and has a limited range of motion. He could open and close that hand, but not much else. He had tried other robotic arms over the years, but they had similar problems.

“They’re just not powerful enough,” he said. “There’s a huge delay between performing a function and having the prosthesis actually perform that function. In my daily life, it’s faster to find other ways to do things.

Lately, he’s been experimenting with a new system developed by Austin startup Phantom Neuro that has the potential to provide more realistic control prosthetic limb. The company is making a thin, flexible muscle implant that would allow amputees to achieve a wider, more natural range of motion simply by thinking about the gestures they want to make.

“Not many people are using robotic limbs, largely because the control systems are so bad,” said Connor Glass, CEO and founder of Phantom Neuro.

In a study conducted by Phantom, 10 participants used a wearable version of the company’s sensor to control a robotic arm already on the market, achieving 11 hand and wrist gestures, according to data shared exclusively with WIRED. 93.8% average accuracy. Smith was one of the participants, and the other nine were able-bodied volunteers, as was common in early prosthetic limb research. The success of this research paves the way for future testing of Phantom’s implantable sensors.

Current myoelectric prostheses, like the one Smith tried, read electrical impulses from surface electrodes located on the amputated stump. Most robotic prostheses have two electrodes, or recording channels. When a person flexes their hand, the arm muscles contract. These muscle contractions still occur when an upper limb amputee bends. Electrodes receive electrical signals from these contractions, interpret them, and initiate the movement of the prosthetic limb. But surface electrodes don’t always capture stable signals because they can slide and move, which reduces their accuracy in real-world environments.