A bionic hand that restores amputees' sense of touch is set to change the lives of thousands who have lost limbs, claim scientists. Two middle-aged men who lost their right hands in horrific accidents at work have revealed how the device has given them back their independence over the last two years. Keith Vonderhuevel, 51, from Ohio, is now able to pick up his grandchildren - and actually'feel' their hands for the first time. And Igor Spetic, 52, also from Ohio, has been filmed at home brushing his teeth, combing his hair, cutting eggs and tomatoes and drizzling mayonnaise. Named'Sensation', the bionic hand could revolutionise the treatment of maimed members of the Armed Forces, its developers claim.

The Modular Prosthetic Limb will help patients to feel and manipulate objects just as they would with a native hand. Sitting motionless in her wheelchair, paralysed from the neck down by a stroke, Cathy Hutchinson seems to take no notice of the cable rising from the top of her head through her curly dark hair. Her gaze never wavers as she mentally guides a robot arm beside her to reach across the table, close its grippers around the bottle, then slowly lift the vessel towards her mouth. Only when she finally manages to take a sip does her face relax into a luminous smile. This video of 58-year-old Hutchinson illustrates the strides being taken in brain-controlled prosthetics1.

On a bitter, soul-shivering, damp, biting gray February day in Cleveland--that is to say, on a February day in Cleveland--a handless man is handling a nonexistent ball. Igor Spetic lost his right hand when his forearm was pulped in an industrial accident six years ago and had to be amputated. In an operation four years ago, a team of surgeons implanted a set of small translucent "interfaces" into the neural circuits of his upper arm. This afternoon, in a basement lab at a Veterans Administration hospital, the wires are hooked up directly to a prosthetic hand--plastic, flesh-colored, five-fingered, and articulated--that is affixed to what remains of his arm. The hand has more than a dozen pressure sensors within it, and their signals can be transformed by a computer into electric waves like those natural to the nervous system. Since, from the brain's point of view, his hand is still there, it needs only to be recalled to life. With the "stimulation" turned on--the electronic feed coursing from the sensors--Spetic feels nineteen distinct sensations in his artificial hand. Above all, he can feel pressure as he would with a living hand. "We don't appreciate how much of our behavior is governed by our intense sensitivity to pressure," Dustin Tyler, the fresh-faced principal investigator on the Cleveland project, says, observing Spetic closely. "We think of hot and cold, or of textures, silk and cotton. But some of the most important sensing we do with our fingers is to register incredibly minute differences in pressure, of the kinds that are necessary to perform tasks, which we grasp in a microsecond from the feel of the outer shell of the thing. We know instantly, just by touching, whether to gently squeeze the toothpaste or crush the can." With the new prosthesis, Spetic can sense the surface of a cherry in a way that allows him to stem it effortlessly and precisely, guided by what he feels, rather than by what he sees. Prosthetic hands like Spetic's tend to be super-strong, capable of forty pounds of pressure, so the risk of crushing an egg is real. The stimulation sensors make delicate tasks easy. Spetic comes into the lab every other week; the rest of the time he is busy pursuing a degree in engineering, which he has taken up while on disability.