Fabrizio wasn't sure what to expect of his newly outfitted prosthetic hand, until he touched one of the researchers who'd given it to him.
"When one of the researchers placed the sensor on his own body, I could feel the warmth of another person with my phantom hand,"said Fabrizio, a 57-year-old man from Pistoia, Italy. "It was a very strong emotion for me, it was like reactivating a connection with someone."
Fabrizio -- who lost his hand 37 years ago -- experienced that sensation thanks to cutting-edge sensors installed in the prosthetic hand, according to a report published Feb. 9 in the journal Med.
Those sensors provide realistic and real-time thermal feedback to the wearer.
With the hand, Fabrizio was able to discriminate between and manually sort objects of different temperatures. Researchers did not provide Fabrizio's last name.
This is the first time that natural temperature sensation has been incorporated into a functional artificial limb, the researchers said.
"Temperature is one of the last frontiers to restoring sensation to robotic hands. For the first time, we're really close to restoring the full palette of sensations to amputees,"said co-senior study author Silvestro Micera, a professor of biorobotics research at the Sant'Anna School of Advanced Studies in Pisa, Italy.
The "MiniTouch"device uses off-the-shelf electronics and doesn't require any surgery to restore temperature sensation to patients, the researchers noted.
"This is a very simple idea that can be easily integrated into commercial prostheses,"Micera said in a university news release.
For the study, researchers linked the device to a point on Fabrizio's remaining forearm that caused him to experience thermal sensations from a phantom index finger.
Using the MiniTouch, Fabrizio was able to discriminate with perfect accuracy between bottles containing water that was 53 degrees (cold), 75 degrees (cool) and 104 degrees Fahrenheit (hot), results show. Without the device, Fabrizio's accuracy fell to just 33%.
Fabrizio also was able to differentiate while blindfolded between human and prosthetic arms with 80% accuracy, thanks to the sensation of warmth provided by the MiniTouch. Without the device, his accuracy fell to 60%.
"Adding temperature information makes the touch more human-like,"said co-senior researcher Solaiman Shokur, chair of translational neuroengineering with École Polytechnique Fédérale de Lausanne in Switzerland. "We think having the ability to sense temperature will improve amputees' embodiment -- the feeling that 'this hand is mine.'"
This sort of feedback is critical to creating a prosthetic hand that can perform as well as a real one, Shokur said.
"When you reach a certain level of dexterity with robotic hands, you really need to have sensory feedback to really be able to use the robotic hand to its full potential,"Shokur explained.
"Our goal now is to develop a multimodal system that integrates touch, proprioception [sense of self-movement] and temperature sensations,"Shokur added. "With that type of system, people will be able to tell you 'this is soft and hot,' or 'this is hard and cold.'"
More information
The National Institutes of Health has more about artificial limbs.
SOURCE: Sant'Anna School of Advanced Studies, news release, Feb. 9, 2024; Cell Press, news release, Feb. 9, 2024
