Muscle Implants Could Enable Mind-controlled Prosthetics—Without Brain Surgery

Alex Smith was He was 11 years old when he lost his right arm in 2003. A drunk boater collided with his family’s boat on Lake Austin, causing him to capsize. He hit a propeller and his arm was severed underwater.

A year later, he received one electromechanical arma type of prosthesis powered by electrical signals in the muscles of the residual limb. But Smith hardly used it because it was “very, very slow” and had a limited range of motion. He can open and close his hands, but not much else. He tried other robotic arms over the years, but they all had the same problem.

“They don’t have a transcendent function,” he said. “There’s a big delay between performing a function and then having the prosthesis actually do it. In my daily life, it becomes quicker to find other ways to do things.”

Recently, he’s been testing a new system from Austin-based startup Phantom Neuro, which has the potential to provide more lifelike control. prosthetic limbs. The company is building a thin, flexible muscle implant to allow amputees a wider, more natural range of movement simply by thinking about the gestures they want to make.

“Not many people use robotic limbs, and that’s largely because the control system is terrible,” said 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 sensor to control a robotic arm already on the market, achieving high accuracy. The average accuracy was 93.8% across 11 hand and wrist gestures. Smith was one of the participants, while the other nine were volunteers in good physical condition, as was common in early studies of prosthetic limbs. The success of this study paves the way for future testing of Phantom implantable sensors.

Current myoelectric prostheses, like the ones Smith tried, read electrical pulses from surface electrodes placed on the amputated stump. Most robotic prostheses have two electrodes or recording channels. When a person bends their hand, their arm muscles contract. Those muscle contractions still occur in upper-limb amputees when they bend. Electrodes pick up electrical signals from those contractions, interpret them, and initiate movements in the prosthesis. But surface electrodes don’t always capture a stable signal because they can slip and move around, reducing their accuracy in real-world environments.