WASHINGTON — To feel what you touch — that’s the holy grail for artificial limbs.
In a step toward that goal, European researchers created a robotic hand that let an amputee feel differences between a bottle, a baseball and a mandarin orange.
The patient only got to experiment with the bulky prototype for a week, and it’s far from the bionics of science fiction movies. But the research released Wednesday is part of a major effort to create more lifelike, and usable, prosthetics.
“It was just amazing,” said Dennis Aabo Sorensen of Aalborg, Denmark, who lost his left hand in a fireworks accident a decade ago and volunteered to pilot-test the new prosthetic. “It was the closest I have had to feeling like a normal hand.”
This isn’t the first time scientists tried to give some sense of touch to artificial hands; a few other pilot projects were reported in the U.S. and Europe. But this newest experiment, published in the journal Science Translational Medicine, shows Sorensen not only could tell differences in the shape and hardness of objects, he also could quickly react and adjust his grasp.
“It was interesting to see how fast he was able to master this,” said neuroengineer Silvestro Micera of Switzerland’s Ecole Polytechnique Federale de Lausanne, who led the Swiss and Italian research team. “He was able to use this information immediately in a quite sophisticated way.”
Scientists have made great strides in recent years in improving the dexterity of prosthetics. But the sense of touch has been a much more difficult challenge, and is one reason many patients don’t use their prosthetic hands as much as they’d like.
Consider: Grab something and your hand naturally grasps with just enough force to hang on. Users of prosthetic hands have to carefully watch every motion, judging by eye instead of touch how tightly to squeeze. The results can be clumsy, with dropped dishes or crushed objects.
“You always have to look and see what’s going on, so that’s what is so much different from this new hand that I tried,” Sorensen, 36, said in a telephone interview.
First, doctors at Rome’s Gemelli Hospital implanted tiny electrodes inside two nerves — the ulnar and median nerves — in the stump of Sorensen’s arm.
Those nerves normally would allow for certain sensations in a hand. When researchers zapped them with a weak electrical signal, Sorensen said it felt like his missing fingers were moving, showing the nerves still could relay information.
Meanwhile, Micera’s team put sensors on two fingers of a robotic hand, to detect information about what the artificial fingers touched.