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In an ordinary lab at the University of Michigan, Joseph Hamilton, of Flint, does the also-ordinary: He grabs a shiny ball and a bottle; he presses buttons and stacks little cubes; he zips and unzips zippers. Well, it would be ordinary if Hamilton wasn’t an amputee doing this all with a robotic hand—à la Luke Skywalker—and if he wasn’t a test subject for a major advance in the control of robotic limbs.

“It worked awesome,” Hamilton says of his test run with the robotic hand. “If it was something that I had access to for daily use, it would make life so much easier.”

Up until this point, researchers have succeeded in giving amputees control over robotic hands by measuring nerve activity in the residual limb. That signal is extremely faint, resulting in clunky control of the prosthesis—the wearer may need to flex their shoulder to get the device’s thumb to move, for instance. But writing today in the journal Science Translational Medicine, researchers describe a clever way to amplify these signals for users like Hamilton. It’s so effective, participants can put on the robotic hand and pull off fine motor functions right away, no training required.

It all comes down to how the patients regrow their nerves. When a person loses, say, their arm from the elbow down, all their nerves want to grow back where they were before. “Patients get this big ball of nerves called a neuroma,” says University of Michigan plastic surgeon Paul Cederna, who codeveloped this new system. “And that can lead to pain and can prevent them from wearing their prosthesis and severely impact their quality of life.”