When someone has lost a limb to amputation a common problem is "phantom pain." The limb is gone, but the brain is still signaling the missing part and the short-circuit can create a sensation of pain in a body part that doesn't exist.
Researchers at Johns Hopkins University have used that illusion to engineer an electronic skin that can be layered on top of prosthetic limbs. The benefit of what the team is calling, "e-dermis" is that patients can have the sense of touch returned, even though their hand or arm is gone.
While a limb that has been amputated is gone, pain signals, like those of touch, are sent along peripheral nerves. The e-dermis created by JHU engineers is made from rubber and fabric and equipped with sensors that are made to replace the function of nerve endings from the missing limb. The e-dermis is stretched over a prosthetic hand and sends the signals picked up by the sensors to the peripheral nerves and on to the brain.
Luke Osborn, a graduate student in biomedical engineering at JHU who worked on the study explained, "We've made a sensor that goes over the fingertips of a prosthetic hand and acts like your own skin would. It's inspired by what is happening in human biology, with receptors for both touch and pain. 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."
The study showed that while the affected limb might be gone, it is possible to return a sense of touch, almost exactly like a human limb, to patients who have suffered the devastating experience of losing an arm or hand. The team hopes to expand the work for use in lower limb prosthetics as well. Being able to sense a feeling similar to pain could alert patients to damage to their prosthesis. The paper's senior author, Nitish Thakor, a professor of biomedical engineering and director of the Neuroengineering and Biomedical Instrumentation Laboratory at Johns Hopkins is the senior author of the work. He is also the co-founder of Infinite Biomedical Technologies. It's a Baltimore-based company that provided the prosthetic hardware used in the study and could possibly market the technology in the future. Thakor stated, "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."
The work is published in the June 20, 2018 issue of the journal Science Robotics. Several departments at JHU, including Biomedical Engineering, Electrical and Computer Engineering, and Neurology were involved with the work as well as researchers at the Singapore Institute of Neurotechnology. Take a look at the video to learn more about this high-tech neurological advance for amputees.