The latest bionic hand can do a lot more than just let its wearer hold things: it can actually let them feel. By hooking into nerves in an amputee's arm, the new prosthetic can let a person tell how hard or soft an object is and even distinguish its basic shape. "The sensory feedback was incredible," Dennis Sørensen, who wore the hand during its first trial, says in a statement.
"It is very intuitive."
The research was led from EPFL in Switzerland and SSSA in Italy, and its success is being detailed today in Science Translational Medicine. The work is part of a project called Lifehand 2 — a followup to the original Lifehand prosthetic, which featured a similarly complex form but was controlled by the mind, rather than muscle movements. Corresponding author Silvestro Micera actually announced the new prosthetic last year, but the trial wasn't completed until later.
"What was amazing in the subject was the possibility to get — very quickly, almost immediately — the ability to use this restored sense of modality in an effective way," Micera tells The Verge. Though health regulations limited Sørensen's trial to only a month, by the final week he was able to differentiate between three shapes with 88 percent accuracy and between the hardness of three objects with 78.7 percent accuracy. "It is very intuitive," Micera says.
Using the bionic hand required Sørensen to have electrodes implanted in his arm, just above where it had been amputated nine years prior. Even though the nerves hadn't been in use, the prosthetic was able to translate the bionic hand's input into electrical signals that the nerves could understand.
The next step is long-term trials
During the test, Sørensen was asked to differentiate and handle six different objects. For testing hardness, he was given a piece of wood, a stack of plastic glasses, and a pack of cotton. To test how well the prosthetic could relay the feeling of different shapes and sizes, Sørensen was given a bottle, a baseball, and a mandarin orange. Being able to differentiate between objects and hardness also let Sørensen more effectively control how much force the bionic hand exerted while holding different materials.
All images credit of Lifehand 2 and Patrizia Tocci.
While other bionic hands have presented the ability to feel before, Micera can lay out where his research group's will go from here. Next up, they intend to conduct a long-term trial with more patients. "What we are planning now is to have two or three patients long term, everything implanted," Micera says.
The paper also suggests that this prosthetic or future versions of it may be capable of conveying more information. "I know that we can do more," Micera says. "How much we can go further is difficult to say. To make it extremely simple: from 3 objects to 100 objects, I don't know. But from 3 objects to 5 or 6, probably."