New device to allow sensations in prosthetic hands

Scientists have designed a novel device to allow those with upper limb prosthetics to feel hot and cold and the sense of touch through their 'robotic' hands.
Daniel Moran from the Washington University in St Louis is testing the device that would stimulate the nerves in the upper arm and forearm.
If it works, upper-limb amputees who use motorised prosthetic devices would be able to feel various sensations through the prosthetic, which would send sensory signals to the brain, researchers said.
Moran and his team developed an electrode designed to stimulate sensory nerve cells in the ulnar and median nerves in the arms.

The ulnar nerve, one of three main nerves in the forearm, is the largest nerve in the body unprotected by muscle or bone and is connected to the ring finger and pinkie finger on the hand.
It is the nerve that is stimulated when you hit your elbow on something and trigger your "funny bone."

The median nerve in the upper arm and shoulder is connected to the other fingers on the hand, so together, the two nerves control movement and sensations including touch, pressure, vibration, heat, cold and pain in all of the fingers.
People using arm prosthetics have to rely on their vision to use them properly, Moran said.

To pick up a cup of coffee, they have to be able to see the cup, place the fingers of the prosthesis around it and lift it.
They are unable to feel whether the cup is in their hand, if the cup is hot or cold or if they are about to drop it. By enabling the ability to feel, users will have more control over the prosthesis.
Researchers have developed a macro-sieve peripheral nerve interface designed to stimulate regeneration of the ulnar and median nerves to transmit information back into the central nervous system.
The macro-sieve is made of an ultra-thin, flexible material similar to a soft contact lens, is about 1/8th the size of a dime and looks like a wagon wheel with open spaces between the "spokes" that allow the nerve to grow.

Wilson Ray, assistant professor of neurological surgery at the School of Medicine; will implant the electrode into the ulnar and median nerves in the forearms of nonhuman primates to determine the amount of sensory information that is encoded by directly stimulating small groups of peripheral nerves.
They also will implant a cuff electrode, the current standard of care, to compare the performance.