Bionic hand moves, grasps, even lets you “feel”

Researchers from several European countries and universities have collaborated to make a bidirectional electronic hand that moves, grasps and can even let you “feel” an object.

Artificial hands aren’t new. The first crude artificial hands date back thousands of years. Originally they were used primarily for cosmetic purposes only. Then, gradually, some functionality was added. The carved wooden “hand” was replaced with a hook that at least allowed for some function.

Fast forward in time and the prosthetic hand became more and more natural. Research, sensors, computer chips, plastics and motors allowed for prosthetic hands that could actually open and close after they were implanted on an amputee. With practice, the human half to the bionic hand could learn to carefully pick up a china plate or crush a rock. He could use a screwdriver to repair a computer, hold a baby or help lift a sofa. But he had to practice without any sensory input from the hand itself. That is, he had to judge how much force to exert based on what he saw, how heavy the object felt when he lifted it, how it appeared to him. The hand itself gave him no feedback as to how the object felt.

Until now.

Prof. Silvestro Micera with LifeHand2. (Photo courtesy of Università Campus Bio-Medico di Roma)

Prof. Silvestro Micera with LifeHand2. (Photo courtesy of Università Campus Bio-Medico di Roma)

When we pick something up, millions of sensory nerves are activated. Even with our eyes closed we get an appreciation of the object’s weight, thickness, position, consistency, temperature, shape and other information. The sensory nerves in the hand feed into larger nerves in the arm, then to the spinal cord and ultimately to the brain. The brain integrates all of the information and tells the hand what to do: how much force to use, where the best place is to pick up the object, how fragile it is, etc.

Someone using an electronic prosthetic hand never got those cues.  The robotic hand couldn’t sense or transmit information to the brain. But this new electronic hand can do just that.

It’s now a two-way now. The hand signals the brain, and the brain signals the hand. Sensors in the fingers of the hand are activated when something touches them. They send signals to a computer that transmits signals to the amputee’s remaining, intact nerves in his arm. From there the information goes to the brain. The brain then signals the hand to do what is necessary: touch, grasp, lift, etc.

Dennis Sorensen, a 39 year-old amputee got to try the hand out. He said that he was amazed that he could feel something in his “hand” (which was amputated following a fireworks explosion almost 10 years ago.) He said that he could feel “soft things, hard things and round things.”

Doctors removed the hand after about a week.

Dennis Sorenson, a patient using the new LifeHand2.

Dennis Sorensen, a patient using the new LifeHand2. (Photo courtesy of Università Campus Bio-Medico di Roma)

For now, the electrode from the hand needs to be attached to the patient’s peripheral nerves. Researchers worry that there is the risk of infection over time if the electrode is left in place for a long period. They are working on alternate methods that could lead to permanent implantation.

Also, they are looking at how to make the hand as cheaply as possible, so that it would be affordable to most who need it, even if they don’t have health insurance.

Close-up of Dennis Sorenson using the LifeHand2.  (Photo courtesy of Università Campus Bio-Medico di Roma)

Close-up of Dennis Sorensen using the LifeHand2. (Photo courtesy of Università Campus Bio-Medico di Roma)

In the planning stage is work on a prosthetic foot that would be able to send signals to the brain about the terrain on which the patient is walking. The brain would then send signals to the motors in the foot and toes to help the patient walk more normally. Researchers are planning to start more trials next year with a small number of amputees to get additional data on how the hand works.

Mark Thoma, MD, is a physician who did his residency in internal medicine. Mark has a long history of social activism, and was an early technogeek, and science junkie, after evolving through his nerd phase. Favorite quote: “The most exciting phrase to hear in science... is not 'Eureka!' (I found it!) but 'That's funny.'” - Isaac Asimov

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