by Whether it’s a simple handshake or a full-body hug, the warmth of another person adds a human touch to social interactions. Now researchers have created a device that allows amputees to experience such natural temperature sensations using their prostheses.
The team says the innovation is a first and paves the way for many sensors to be integrated into artificial limbs.
Professor Solaiman Shokur, senior author of the research at the Swiss Federal Institute of Technology Lausanne, said it was known that boosting sensory feedback from a prosthesis could help people feel that an artificial limb was part of their body.
“To give a natural feel, you can’t do it without temperature,” he said.
Shokur added that this approach could enable people with artificial limbs to detect if something was dangerously hot and help them distinguish between different materials.
“Plus it opens a window to the more social aspect of the encounter,” he said.
Writing in the journal Med, Shokur and his colleagues report that they had previously shown that it was possible to create a person’s sense of heat or cold in an amputated hand by heating or cooling specific points on the rest of their hand.
Building on this phenomenon, the team created the MiniTouch in which a temperature sensor was placed on someone’s prosthetic arm at the location where the phantom thermal sensations appeared to originate.
When the sensor detected a temperature change away from the 32C baseline, it sent a signal to a temperature controller. This relayed the information to another component that was located on the upper part of the prosthesis and contacted the skin of the arm.
The temperature detected by the sensor was then reproduced on the arm at the trigger point for the fault detection. In the current study, the device reproduced temperatures from 20C to 40C.
The result is that the person felt a thermal sensation in his hand was missing, at the location of the temperature sensor.
To test the MiniTouch, the researchers fitted the prosthesis of Fabrizio, a 57-year-old man whose right arm had been amputated below the elbow.
The team found that using the device, Fabrizio could distinguish between identical bottles containing cold, hot, or room temperature water, with 100% accuracy. When the device was switched off, its accuracy was 33%.
Fabrizio was also able to distinguish between copper, glass, and plastic slabs using the MiniTouch when folded, with the same accuracy as when using his other intact hand. Once the device was off, however, his options came down to chance.
In addition, the MiniTouch increased Fabrizio’s ability to distinguish between real and prosthetic arms when he was wearing blindfolds — though his accuracy was higher with his intact arm, Shokur said, possibly because it detected information such as texture too.
The device also improved Fabrizio’s accuracy, though not speed, when sorting a box of hot and cold steel cubes in the space of one minute.
Fabrizio said that the phantom sensation in his missing hand was more intense than in his intact hand when he saw hot or cold cubes.
“When I had my accident at the age of 20, I tried a prosthetic arm that gave me simple movement; instead, with these new technologies, I can better understand what I’m getting into,” he said.
Although the authors say the device should be tested in a larger group of patients, they note that the MiniTouch does not require surgery and is based on readily available electronics – meaning it can be attached on current prosthetics, that it can be easily personalized, and that it is relatively cheap.
Professor Silvestro Micera, another senior author on the paper from the Swiss Federal Institute of Technology Lausanne and the Sant’Anna School of Advanced Studies in Italy, said the team were now planning to create a single wearable system that would enable people with amputate them. experience different sensations using their prostheses – including pressure, texture, position, temperature and wetness.
“This would be for us the [really] the next step,” Micera said.
Dr Sigrid Dupan, an expert in sensory feedback for prostheses at University College Dublin, who was not involved in the study, said the fully integrated system is a major step forward in research into thermal feedback for artificial limbs, and that it could help people feel. prostheses were part of their bodies.
But she cautioned that the team had previously shown that it was not possible to induce thermal sensations in everyone with amputation, although they were inconsistent in some people.
“I’m excited about the research and it shows promising developments, but … people can’t expect to implement these new devices in our health care system in a short period of time,” she said.
