Sensory feedback is important for amputees to be able to explore and interact with their environment. Now, researchers have developed a device that allows amputees to sense and respond to temperature by delivering thermal information from the prosthetic fingertip to the amputee’s remaining limb. The device “MiniTouch”, presented on February 9 in the magazine with, uses off-the-shelf electronics, can be integrated into commercially available prosthetic limbs, and does not require surgery. Using the thermally sensitive prosthetic hand, a 57-year-old transradial amputee was able to manually distinguish and sort objects of different temperatures and sense bodily contact with other people.
This is a very simple idea that can be easily integrated into commercial prostheses. Temperature is one of the final frontiers in restoring sensation to robotic hands. For the first time, we are really close to restoring the full range of sensations to amputees.”
Silvestro Micera, senior author of École Polytechnique Fédérale de Lausanne and Scuola Superiore Sant’Anna
The team previously showed that their thermosensitive technology could restore passive thermosensing in 17/27 amputees. In the new study, they show that MiniTouch can be easily integrated into commercial prosthetic limbs and that it enables active thermogravity during tasks that require feedback between sensory and motor neurons.
Beyond the functional importance of the ability to sense heat and cold, thermal information can also enhance amputees’ sense of embodiment and their ability to experience affective touch. “Adding temperature information makes the touch more human,” says senior author Solaiman Shokur (@SolaimanShokur) of École Polytechnique Fédérale de Lausanne. “We think the ability to sense temperature will improve amputees’ embodiment — the feeling that ‘this hand is mine’.”
To do this, they integrated the MiniTouch into the personal prosthesis of a 57-year-old man who had undergone a transradial amputation 37 years earlier by attaching the device to a point on the participant’s remaining limb that elicited thermal sensation in the index finger. his ghost. . Next, they tested his ability to distinguish between objects of different temperatures and objects made of different materials.
Using the MiniTouch, the participant was able to discriminate between three visually indistinguishable bottles containing cold (12°C), cold (24°C), or hot (40°C) water with 100% accuracy, while his device. accuracy was only 33%. The MiniTouch device also improved its ability to quickly and accurately sort metal cubes of different temperatures.
“When you reach a certain level of dexterity with robotic hands, you really need to have sensory feedback to be able to use the robotic hand to its full potential,” says Shokur.
Finally, the MiniTouch device improved the participant’s ability to distinguish between human and prosthetic arms while blindfolded—from 60% accuracy without the device to 80% with the device. However, his ability to sense human touch through his prosthesis was still limited compared to his uninjured arm, and the researchers speculate that this was due to limitations in other non-thermal sensory inputs, such as the softness and texture of the skin. Other technologies are available to enable these other sensory inputs, and the next step is to begin integrating these technologies into a single prosthetic limb.
“Our goal now is to develop a multimodal system that integrates touch, proprioception and temperature sensations,” says Shokur. “With that kind of system, people will be able to tell you ‘this is soft and hot’ or ‘this is hard and cold’.”
The researchers say their technology is technically ready for use, but more safety tests are needed before it reaches the clinic, and they have plans to further improve the device so it can be deployed more easily. Future models could also build on Minitouch to integrate thermal information from multiple points on an amputee’s phantom limb—for example, by allowing people to distinguish between thermal and tactile sensations in the finger and thumb, it could help them understand a hot drink while enabling sensation on the back of the hand can improve the sense of human connection by allowing amputees to feel when another person touches their hand.
This research was supported by the Bertarelli Foundation, the Swiss National Science Foundation, the European Union’s Horizon 2020 research and innovation program, the Horizon Europe Research and Innovation Program and the Ministry of University and Research.
Muheim, J., et al. (2024) A sensory-motor hand prosthesis with integrated thermal feedback. With. doi.org/10.1016/j.medj.2023.12.006.