Robotic Hand Restores Wearer’s Sense of Touch

A prosthetic hand powered by its wearer’s thoughts has restored a semblance of touch to a man whose arm was amputated below the elbow 17 years ago.

As researchers from the University of Utah report in the journal Science Robotics, the “LUKE arm”—named in honor of Star Wars hero Luke Skywalker, who lost his lost his hand to Darth Vader’s lightsaber in The Empire Strikes Back—enabled real estate agent Keven Walgamott to pluck grapes from the stem, pick up an egg without cracking its shell and even hold his wife’s hand.

“It almost put me to tears,” Walgamott, who lost his left hand and part of his arm in an electrical accident, says in a press release. “It was really amazing. I never thought I would be able to feel in that hand again.”

According to Scientific American’s Jeffery DelViscio, a team led by biomedical engineer Jacob George stimulated electrodes implanted in Walgamott’s forearm nerves to determine which circuits triggered 119 “sensory precepts,” or touch sensations such as vibration, pressure, pain, tightening, movement, tapping and buzzing. Next, the scientists mapped this information onto the robotic hand, creating what George calls a “good approximation of the same information [the subject] would be getting from their natural hand.”

When Walgamott thought about moving his bionic hand in a certain manner, the electrodes in his forearm conveyed these directions to an outside computer. This digital system, Anna Ploszajski writes for the Guardian, guided the prosthetic’s movements while sending back electrical signals capable of helping the brain mimic the feeling of touch—a key breakthrough George says is grounded in “the body’s natural language.”

Speaking with NPR’s Luisa Torres, George adds, “We're tapping into the same [mechanism] that's used in my body and your body and everyone's body, and we're trying to just activate it in the way it would have normally been activated. So the sensations feel like they're coming from their hand.”

The LUKE arm isn’t the first prosthetic to provide users with sensory feedback, but as DelViscio notes for Scientific American, the system does prioritize subtle sensation to a previously unseen extent. In trials, Walgamott was able to rapidly judge objects’ texture and size even when blindfolded; by gauging whether he was holding an egg or a grape, for example, the amputee was able to adjust his grip to avoid crushing the item.

According to the Guardian’s Ploszajski, the scientists have been working on their bionic limb for around 15 years. In its current form, the hand, equipped with 19 touch and positioning sensors, can move in six directions.

Moving forward, George and his colleagues hope to create a portable version of the LUKE arm because as of now, the device must be connected to a stationary computer, meaning Walgamott and other test subjects can only use it in the lab. They also hope to increase the prosthetic’s sensitivity to information including pain and temperature and figure out how to actually bring the system onto the market. Per Scientific American, the per-unit cost is expected to be between $100,000 to $200,000—a price tag the scientists hope health insurers will be willing to cover.

Insurance companies “think of [a sense of touch] as a luxury,” Sharlene Flesher, a researcher at Stanford University who was not involved in the study, tells NPR’s Torres. "But [a sense of touch] really is so critical to how you control your arm."

Pending federal regulatory approval, study co-author Gregory Clark says in the press release, three test subjects currently working with the LUKE arm may be able to take the prosthetic home by 2020 or 2021.

For Walgamott, wearing the robotic hand was a “remarkable experience.” In addition to handling fragile items, he was able to load a pillow into a pillowcase, send a text message and peel a banana.

Still, Clark notes, none of these activities were Walgamott’s first priority: “One of the first things he wanted to do was put on his wedding ring,” the researcher concludes. “That’s hard to do with one hand. It was very moving.”

Meilan Solly | | READ MORE

Meilan Solly is Smithsonian magazine's associate digital editor, history.