“When one of the researchers placed the sensor on his own body, I could feel the warmth of another person with my phantom hand. it was a very strong emotion for me, it was like reactivating a connection with someone”. Thanks to a sensorised prosthetic hand that provides realistic and real-time thermal feedback, Fabrizio, a 57-year-old man from Pistoia with a transradial (wrist) amputation, was able to discriminate between and manually sort objects of different temperatures or materials and sense bodily contact with other humans. The new technology is presented in a study published today in the journal Med (Cell Press); the work is the result of a scientific collaboration between the Sant’Anna School of Advanced Studies in Pisa (Italy) and École Polytechnique Fédérale de Lausanne (Switzerland). This is the first time that natural temperature sensations are incorporated in a functional artificial limb. “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” says Professor Silvestro Micera (Sant’Anna School of Advanced Studies and EPFL), joint senior author of the study.
Sensory feedback is one of the most important steps to allowing people with an amputation to interact with their environment. Building on previous findings on phantom thermal sensations (stimulation of specific points on the residual arm to evoke perceptions in the missing hand), researchers have developed a device, the 'MiniTouch', which allows amputees to perceive and respond to temperature by transmitting thermal information from the fingertip of the prosthetic hand to the amputee's residual arm. The device uses off-the-shelf electronics, can be integrated into commercially available prosthetic limbs, and does not require surgery. “This is a very simple idea that can be easily integrated into commercial prostheses” adds Micera. “Adding temperature information makes the touch more human-like,” says dr. Solaiman Shokur, joint senior author, of École Polytechnique Fédérale de Lausanne. “We think having the ability to sense temperature will improve amputees’ embodiment—the feeling that ‘this hand is mine’.” “Up to now, thermal sensations have been very much neglected in neuroprosthetics research even if there is increasing evidence of their importance in our everyday life. We think that amputee individuals could benefit from regaining temperature sensations well beyond the detection of cold or warm objects” says Jonathan Muheim, PhD student at EPFL and co-first author of the paper.