Dennis Aabo Sørensen may be missing a hand, but he nonetheless recently felt rough and smooth textures using a fingertip on that arm. The fingertip was electronic, and was surgically hard-wired to nerves in his upper arm. He is reportedly the first person in the world to recognize texture using a bionic fingertip connected to electrodes that were surgically implanted above his stump.
The device was created by scientists from the Ecole polytechnique fédérale de Lausanne (EPFL) in Switzerland, and Italy's Scuola Superiore Sant'Anna (SSSA) research institute.
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While it was wired to Sørensen, a machine moved it across rough and smooth plastic surfaces. Sensors in the fingertip generated electrical signals as they deformed in response to the topography of those surfaces, and transmitted those signals to the nerves in a series of electrical spikes – this was reportedly an imitation of the "language of the nervous system." He was able to differentiate between the two surfaces with an accuracy of 96 percent.
"The stimulation felt almost like what I would feel with my hand," he said. "I still feel my missing hand, it is always clenched in a fist. I felt the texture sensations at the tip of the index finger of my phantom hand."
Sørensen had previously been the test subject for a complete touch-sensing prosthetic hand, although it was less sensitive than the fingertip.
Non-amputees were also able to feel via the fingertip, albeit with a lower average accuracy of 77 percent. In their case, it was connected to their arm nerves simply via fine needles that pierced the skin. The fact that it worked for them is significant, because it means that further development of the technology won't necessarily require amputees as test subjects.
Additionally, it may find use in areas other than prosthetics. "It will also be translated to other applications such as artificial touch in robotics for surgery, rescue, and manufacturing," said SSSA's Calogero Oddo.
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