Engineers at Ecole Polytechnique Fédérale de Lausanne (EPFL) in Switzerland have developed a new technology that can provide temperature feedback for amputees using a prosthetic limb. Excitingly, the device makes it feel as if the temperature sensation is experienced in the phantom limb, providing a realistic experience of touching something cold or hot with the missing limb. The system consists of a temperature sensor that is placed on the finger of a prosthetic hand, for example, and then thermal electrodes that can generate cold or heat are placed on the skin of the residual arm. When the finger sensor encounters something hot or cold, the thermal electrodes convey this to the residual limb, but the user experiences it as if the feeling is directly in their missing finger.
Prosthetics are undergoing many exciting developments, from robotic mechanisms to technologies that are designed to restore a sense of touch. This latest technology provides temperature sensation for prosthetic wearers, but this is not just a simple indication if a surface is hot or cold, but a feeling that is experienced within the phantom limb itself, helping amputees to reconnect with their missing limb.
“Temperature feedback is a nice sensation because you feel the limb, the phantom limb, entirely,” said Francesca Rossi, an amputee from Italy who has been trialing the new system. “It does not feel phantom anymore because your limb is back.”
The researchers discovered that applying heat or cold to areas of the residual limb can lead to the feeling being experienced within the phantom limb. Not only that, but stimulating different regions of the residual limb can lead to the feeling being experienced in different parts of the phantom limb, such as different fingers. This varied for each user, but suggests that with a little tailoring, technology could provide a proxy for such phantom limbs, with different areas of the limb being amenable to separate stimuli.
“Temperature feedback is essential for relaying information that goes beyond touch, it leads to feelings of affection. We are social beings and warmth is an important part of that,” said Silvestro Micera, a researcher involved in the study. “For the first time, after many years of research in my laboratory showing that touch and position information can be successfully delivered, we envisage the possibility of restoring all of the rich sensations that one’s natural hand can provide.”
See a video about the technology below.
Study in journal Science: Restoration of natural thermal sensation in upper-limb amputees