Advances in prosthetics have come a long way, with sophisticated mechanical arms that can grip better or legs that can run faster than previous generations. Yet, they still can’t emulate the real thing in terms of feeling or sense of touch.
But that might be changing with an advancement in technology from Johns Hopkins University in the form of an electronic skin that recreates a sense of touch as well as pain by sensing stimuli and relaying the impulses back to the peripheral nerves.
The sensory device is made of fabric and rubber laced with sensors to mimic nerve endings and goes over the fingertips of a prosthetic hand, acting like skin would normally.
"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,” said Luke Osborn, a graduate student in biomedical engineering at JHU.
The technology could possibly restore a range of natural, touch-based feelings to amputees who use prosthetic limbs. The ability to detect pain could be useful for prosthetic hands and lower limbs as it would alert users to potential damage to the prosthetics.
Incorporating pain into the electronic skin was important because it is an essential, protective sense of touch. Current prostheses help amputees' ability to regain lost function but often lack meaningful tactile feedback or perception, Osborn said.
Stimulating peripheral nerves in the arm to convey a sense of touch makes a so-called phantom limb come to life and enables its user to sense a continuous spectrum of tactile perceptions — from light touch to noxious or painful stimulus, JHU said.
"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 Nitish Thakor, professor of biomedical engineering at John Hopkins and co-founder of Infinite Biomedical Technologies, a prosthetic hardware vendor.
How They Did It
The team created a “neuromorphic model” that mimics the touch and pain receptors of the human nervous system, allowing the e-dermis to electrically encode sensations similar to human skin. Using electroencephalography (EEG), John Hopkins was able to see that test subjects could perceive sensations in a phantom hand.
The e-dermis was connected by using a noninvasive method known as transcutaneous electrical nerve stimulation (TENS) and test subjects were able to experience a natural, reflexive reaction to both pain while touching a pointed object and non-pain when touching a round object.
Researchers said this technology could also be used to make robotic systems more human or even extend to astronaut gloves and space suits.
The next steps are to develop the technology further and work to better understand how to provide sensory information to amputees in the hopes of making the system ready for widespread use.
The full research can be found in Science Robotics.