A bionic hand with a sense of touch has been tested on a patient for the first time, raising the prospect of artificial 'feeling' limbs.
Dennis Sorensen, from Denmark, was able to feel the shape and texture of objects using the robot left hand connected by ultra-fine electrodes to nerves in his upper left arm.
"The sensory feedback was incredible," said the 36-year-old, who spent a month trying out the hand. "I could feel things that I hadn't been able to feel in over nine years. When I held an object, I could feel if it was soft or hard, round or square."
Sorensen, who lost his left hand in a fireworks accident, was taking part in a trial in Rome conducted by the Swiss and Italian scientists who developed the experimental prosthetic hand.
The artificial hand detects information about touch using electrical signals from artificial tendons controlling finger movement before fine wires send the digitally refined impulses to four electrodes implanted in the sensory ulnar and median nerves of the upper arm.
"This is the first time in neuroprosthetics that sensory feedback has been restored and used by an amputee in real-time to control an artificial limb," said Dr Silvestro Micera, from the Federal Polytechnique School of Lausanne in Switzerland, who leads the Lifehand 2 project.
Sorensen had the hand fitted on January 26 2013 at Gemelli Hospital in Rome and though the sensory electrodes had to be removed from his arm after one month due to clinical trial safety rules, the scientists believe they would continue to function without damaging the nervous system for many years.
The results of the study, published in the journal Science Translational Medicine, are the first step towards a true bionic hand which can feel as well as move, say the scientists, but they point out that it will be years before such a device becomes commercially available.
Dr Alastair Ritchie, lecturer in biomaterials and bioengineering at the University of Nottingham, said: "This is very interesting work, taking research in upper limb prosthetics into the next stage by adding sensory feedback.
"Our hands are one of our principal interfaces with the world, and in recent years we have seen real advances. This technology would enable the user to know how firmly they are gripping an object, which is vital for handling fragile objects – imagine picking up an egg without any feeling in your fingers.
“Another exciting aspect is the ability of the human brain to learn, allowing the user to become more proficient as he gains experience in using the prosthesis.
"However, the use of a transcutaneous sensor, with the electrodes embedded next to the peripheral nerves, and wires running through the skin, presents biocompatibility challenges and will require rigorous wound care to prevent infection."
Dr David Gow, director of rehabilitation engineering services and bioengineering at NHS Lothian, said: "Although based on a single case study, the results look like a practical surgical-based method of delivering spatial and force information from a robotic hand's sensors back to the user to allow him fine control of force and to gain some knowledge of the shape and stiffness of the object in his artificial grasp.
"This opens up exciting possibilities for artificial limb users and takes us a step closer to a clinically viable man-machine interface."