Electronic skin restores touch and pain sensations to amputees

Researchers at John Hopkins University, Baltimore, USA, have created an electronic skin - dubbed the “e-dermis” - which is capable of restoring touch-based feelings to amputees who wear prosthetic hands.
 
The electronic skin is made from fabric and rubber, filled with an array of sensors to mimic nerve endings, and can be layered over a prosthetic hand.
 
“We’ve made a sensor that goes over the fingertips of a prosthetic hand and acts like your own skin would,” said Luke Osborn, a graduate student researcher at John Hopkins. “It’s inspired by what is happening in human biology, with receptors for both touch and pain.”
 
“Pain is, of course, unpleasant, but it’s also an essential, protective sense of touch that is lacking in the prostheses that are currently available to amputees. Advances in prosthesis designs and control mechanisms can aid an amputee’s ability to regain lost function, but they often lack meaningful, tactile feedback or perception.”
 
E-dermis is inspired by real human skin, which contains an elaborate network of many receptors, which rapidly delay a range of sensations to the brain. When the electronic skin picks up stimuli, it relays impulses back to the peripheral nerves in the arm by gently stimulating the nerves through the skin.
 
The researchers created a neuromorphic model inspired by the receptors in the human nervous system, allowing their electronic skin to send small electric signals which mimicked natural biological signals. This allows the wearer to experience a range of familiar sensations, from a soft touch to sharp pain.
 
The researchers found that their main test subject – who was an amputee – was capable of perceiving artificial sensations in their phantom hand, so they connected the electronic skin to the subject using a method called transcutaneous electrical nerve stimulation. The subject was able to detect painful and non-painful touch sensations when the e-dermis was in contact with different objects and was able to perceive the shape of rounded objects.
 
“For the first time, a prosthesis can provide a range of perceptions – from fine touch to noxious – to an amputee, making it more like a human hand,” said senior author Professor Nitish Thakor, who is also director of John Hopkins’ Biomedical Instrumentation and Neuroengineering Laboratory.
 
The e-dermis can be fitted over an existing prosthetic hand and could easily be adapted for use with a leg or foot prosthesis. The researchers suggest that it could also be used to give robotic systems a better sense of touch, or could be added to the gloves worn by astronauts during missions.

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