A common experience by amputees is phantom limb syndrome, where they can still feel sensations, including pain, in limbs that are no longer there. While these sensations are only perceived, they may soon become a reality thanks to researchers at Johns Hopkins University.
A team of engineers has created an electronic skin for prosthetic hands. This new e-dermis gives amputees a sense of touch through the fingertips. The e-dermis consists of fabric and rubber laced with sensors that mimic nerve endings, which recreates the sensation of touch and pain by sensing stimuli and relaying that information to the person’s peripheral nerves.
“It’s inspired by what is happening in human biology, with receptors for both touch and pain,” said Luke Osborn, a graduate student in biomedical engineering. “This is interesting and new because now we can have a prosthetic hand that is already on the market and fit it with an e-dermis that can tell the wearer whether he or she is picking up something that is round or whether it has sharp points.”
Mimicking the complex network that gives skin the ability to feel was no easy task. The researchers developed a neuromorphic model that recreates the touch and pain receptors of the human nervous system. This allowed the e-dermis to work like real skin and electronically encode sensations. Using an electroencephalography (EEG), the researchers then monitored the brain activity of a test subject, who could perceive these sensations in his phantom hand.
The e-dermis output was then connected to the volunteer through transcutaneous electrical nerve stimulation (TENS). This demonstrated that the “test subject and prosthesis experienced a natural, reflexive reaction to both pain while touching a pointed object and non-pain when touching a round object.”
As the amputee who served as the principal volunteer put it: “After many years, I felt my hand, as if a hollow shell got filled with life again.”
The team plans to continue developing the technology with the goal to eventually make the technology available for widespread use. Besides offering a meaningful sensory experience for amputees, their work can also help to alert amputees to danger.
“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,” Osborn said. “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.”
Interested in more ways technology is innovating the field of medicine? Check out Researchers Create Artificial Nerve System and Six-Legged “Horse” Provides Hippotherapy Alternative.