The MiniTouch device includes a thermal sensor on the fingertip and a thermal stimulator attached to the residual limb. Credit: EPFL/Caillet.
A man whose right hand was amputated at the age of 20 is now able to feel the temperature of the objects he touches with his prosthetic hand, thanks to a new device integrated in it1.
The device, called MiniTouch, was developed last year2 by researchers at the Swiss Federal Institute of Technology Lausanne and the School of Advanced Studies Sant'Anna in Pisa. It is made by two components, an active thermal sensor which measures temperature and generates realistic signals which are then sent to the second component, a thermal stimulator.
MiniTouch was first tested as a standalone device in nearly 20 people at the prosthetic centre of the Italian Institute for Insurance against Accidents at Work (INAIL) near Bologna.
INAIL’s engineers integrated the thermal sensor on the index finger of the prosthetic hand of one patient, and the thermal stimulator into the socket that secures the robotic hand to the forearm, in such a way that it touched a point on the residual limb that aroused thermal sensations in the person's ‘phantom’ index finger — the typical sensation of still having the finger that many amputees have. This point was identified thanks to a neural mapping developed in the previous study.
During eight experimental sessions over six months, the participant could discriminate objects with three different temperatures or made of different materials. He could also discern whether he was touching a silicon arm or a real arm while blindfolded, and grasp and move blocks of different temperature in order to classify them from the hottest to the coldest.
"The richness and realism of the sensations provided to wearers is key to the effectiveness of a prosthesis in replacing a natural limb in daily activities,” says Emanuele Gruppioni, biomedical engineer at INAIL who led the clinical tests.
“As a next step we will work with a new prosthetic hand, developed in collaboration with the Italian Institute of Technology, to improve the MiniTouch integration and have a light and wearable thermal prosthetic hand,” Gruppioni concludes.
