A new artificial skin fitted with sensors can give prosthesis wearers feeling in their fingertips. The development brings prosthetics another step closer to their biological counterpart.
Prosthetics are becoming increasingly sophisticated and offer users more and more possibilities. Despite this, prosthetics still have significant limitations. For instance, wearers have no feeling in their prosthesis. Not only does this make picking up small objects difficult, users cannot feel the structure of an object and cannot experience temperatures. A new artificial skin developed by John Hopkins University does offer these capabilities.
Inspired by human biology
The artificial skin is called 'e-dermis'. "We have developed a sensor that is placed on the fingertips of a prosthetic hand and functions like your own skin would," explains Luke Osborn, a PhD student in biomedical sciences at the university. "It is inspired by human biology, with receptors for touch as well as pain."
"This is interesting and novel as we can now provide a prosthetic hand that is already available with an e-dermis that can tell the wearer whether he or she is picking up something that is round or has sharp edges," Osborn said.
Sensors
The artificial skin consists of a combination of fabric and rubber, which incorporates sensors. These sensors are able to pick up signals normally picked up by receptors in human skin, and translate them into impulses that send to peripheral nerves. The e-dermis is based on human skin, which contains a complex network of receptors. These receptors capture all kinds of stimuli and transmit these stimuli to the brain. The e-dermis artificially mimics this process.
The development allows users to pick up all kinds of stimuli, ranging from a light touch to pain stimuli. "Pain is obviously unpleasant, but it is also an essential and protective sensation that is lacking in prosthetics currently available to amputees," Osborn said. "Developments in prosthetic design and control mechanisms can help amputees regain a function they have lost, but meaningful, tactile feedback or perceptions are often lacking."
Neuromorphic model
The team has therefore developed a 'neuromorphic model' that mimics the touch and pain receptors of the human nervous system, enabling the e-dermis to give users the same impulses as the receptors in human skin would.
During a test, the output of this system was connected to a volunteer using a non-invasive method called 'transcutaneous electrical nerve stimulation' (TENS). In TENS, nerves and muscles are stimulated with an electric current. During tests, the volunteer was found to experience a painful sensation if a pointed object was touched with the prosthesis, while touching a round object did not produce pain sensations. "After many years, I felt my hand again, like an empty shell was filled with life again," said an anonymous amputee who tested the artificial skin in a comment.
The researchers want to further develop their artificial skin and better understand how to deliver useful sensor information to amputees. In time, the researchers hope to make the system widely available.
Author: Wouter Hoeffnagel
Source: John Hopkins University
Source photo: Pixabay / pedrofigueras
