A typical prosthetic arm still looks essentially the way it has for more than a century, with a simple hook that can open and close to squeeze and hold objects. An artificial arm now in development works very differently: The hand on the device is connected to a bracelet that can read muscle signals in an amputee’s stump, so that person can move, tap, and squeeze artificial fingers simply by thinking.
“When you think you want to move—you want to rotate your wrist, or you want to move your fingers—the signal travels from your brain down your spinal cord, and then out the peripheral nerves from the spinal cord into your arm,” says Tyler Hayes, CEO of Atom Limbs, the startup bringing the device to market. “Even when someone has lost or damaged a limb, those nerves are still there and they’re still firing into muscles, it’s just that there’s no real hand left to move. So we listen to the electrical field emanating from your arm, from your muscles, and just tap into that exact signal that your body is sending.” The prosthetic, loaded with 200 sensors, also gives users a sense of touch as they grasp an object. The arm can lift 45 pounds.
The technology was first developed over a decade of research at Johns Hopkins’ Applied Physics Laboratory with a $120 million grant from the Department of Defense. Hayes, a serial entrepreneur, saw a video of an early prototype and reached out to the university, creating a partnership to launch it as a product. “The work for the last six months has just been moving from what you call a research prototype, which is what they have made, to the development prototype that we’re making,” he says.
Some other more advanced prosthetics have recently been developed called myoelectric prostheses. They also use electrodes, but require a user to flex their muscles to make simple movements rather than using thought to control a hand, and they have more limited use. “You cannot move fingers individually,” he says. “You can’t even wiggle your fingers side to side. You literally can go from what you’d call a key grip, for holding your car keys, to a lateral grip for holding a book. It’s just really pre-programmed positions.”
The startup is also working to make the arm more comfortable to wear than older prosthetics, creating a new soft structure system. “Imagine if Nike designed an attachment for artificial limbs to your body,” Hayes says. “It’s that, instead of having to shove your stump into a plastic bucket, and then wear that all day, which people do today.”
Johnny Matheny, who tested three previous versions of the arm as Johns Hopkins developed it, says that there’s no comparison to the hook he uses now. “That’s like asking if the Wright Brothers plane is as useful as a supersonic jet,” he says. Matheny used the artificial arm to do things that wouldn’t have been possible otherwise, including learning to play the piano. The challenge, he says, is whether insurance will pay for it; systems like Medicare don’t even know how to deal with smaller innovations, such as waterproof prosthetics. Bureaucracy needs to change to keep up with technology. “Unemployment doesn’t want to pay people that can get an arm and go back to work in their regular jobs,” he says.”And then you’ve got Medicare, which doesn’t want to approve the new arms for them to be able to do that.”
In the coming year, Atom Limbs plans to begin tests of the newest version of the arm with amputees, while it simultaneously launches a robotic version for industrial use in factories. They aim to bring the prosthetic to market in 2023, with an artificial leg to later follow.