​I Tried Out the ‘Rolls-Royce’ of Prosthetic Hands

Trying out a prosthetic hand with an arm that already has a hand attached is a bizarre experience. Flexing my arm muscles to move the fingers of a Bebio​nic hand, which claims to be the most advanced commercially available prosthetic hand on the market, I felt like my own fleshy digits were rather getting in the way.

I flexed my wrist backwards, then brought it forwards. The index finger of the Bebionic hand stood upright on a table in front of me jabbed twice at the air. This was "mouse grip." I'd just double-clicked.

Kevin Evison, a Bebionic hand user, attested to the hand's abilities. He's been an amputee since 1982 and has been using the Bebionic for 15 months. I asked how it compared to his previous prosthetic. "Blows the other one out the water," he said. "This is the Rolls-Royce of hands." The other, he said, was a Skoda.

He was demonstrating his arm at the Science Museum's "You Ha​ve Been Upgraded" festival, which continues this weekend and showcases enhancements for the body and the brain, from bioelectronic implants to brain caps aiming to improve cognition with electrical current. Here, prosthetics were not positioned as a replacement part, but as a potential improvement.

So I could see how the Bebionic worked, mechanical engineer Martin Wallace placed two small electrodes on just below my elbow, on either side of my arm, and held them in place with a sweatband. These are usually incorporated in the part of the prosthetic that makes contact with the user's body.

The electrodes respond to each of the two muscles tensing. "What the hand is detecting is electrical impulses through the sensors, which are on the surface of the skin," Wallace explained. When I flicked my wrist so my palm faced towards my body, the fingers closed in a grip; when I bent it the other way, the grip opened.

The hand can make 14 differe​nt types of grip, from a precise pinching motion that could hold a pen to a "come hither" finger gesture and a strong fist. Getting to a specific grip requires cycling through them, and occasionally moving the opposable thumb to the preferred position. "When it's your hand and you're wearing it every day, you get to know where those grips are," said Wallace.

It wasn't easy to pick up right away—the trick is to relax your arm so that only one muscle is tense—but Evison said it only took him 15 minutes to really get the hang of it. His arm is also able to rotate at the wrist and, unlike a regular hand, it goes all the way round.

He said he uses the hand for everything, and hasn't found any limits with it. "I use it from the moment I wake up to the moment I go to bed," said Evison. He can't swim with it, and said piano-playing isn't quite there—but he plays guitar with it and demonstrated a typing grip that no doubt comes in handy for his job working in IT. And this is just the start. "Eventually, all the fingers will move independently," he said.

Users amputated above the elbow or shoulder should also be able to use the hand, by placing the electrodes elsewhere. "You just have to find somewhere else on the body to put it—so you find a working muscle, put the electrode on there, and then you learn that that's the muscle you tense to make the hand grip," said Wallace.

The hand may be impressively lightweight and streamlined, but it can pack a punch. Wallace explained that they have to make the fingers stronger than human fingers owing to the lack of biofeedback. While you'd never lean your entire weight on your little finger—it'd hurt—you could put a lot more pressure on the prosthetic without realising it.

"Don't go picking a fight with someone with a prosthetic hand," he said.