Prosthetic Hand Empowers Man to Feel Temperature Using Innovative Device

A groundbreaking device has been developed, allowing a person who has undergone amputation to feel temperature with a prosthetic hand. This technological advancement brings us one step closer to developing prosthetic limbs capable of restoring a full spectrum of sensations, thus improving their usefulness and the wearer's acceptance.

In a joint endeavour by a team of researchers from Italy and Switzerland, a device named "MiniTouch" was fitted onto the prosthetic hand of Fabrizio, a 57-year-old amputee from above the wrist. Through a series of tests, Fabrizio identified cold, cool, and hot bottles of liquid with complete accuracy. He could differentiate between plastic, glass and copper better than by chance and could sort out steel blocks by temperature with an approximate accuracy of seventy-five percent as reported by the researchers on February 9 in Med.

“Incorporating these technologies in ways that can be practically used by prosthesis wearers to perform functional tasks is crucial.” commented neuroengineer Luke Osborn from the Johns Hopkins University Applied Physics Laboratory in Laurel, Md., although he was not part of the research. He further added, “Introducing new sensory feedback systems could grant users greater functionality which they previously could not achieve.”

Furthermore, Fabrizio's ability to distinguish whether he was touching a robotic or human arm was enhanced by the device. His accuracy improved to 80 percent when the device was active, compared to the 60 percent when inactive. This development was marked as notable by neuroengineer Solaiman Shokur of EPFL, the Swiss Federal Institute of Technology in Lausanne, although he admitted it still lagged behind the intact hand due to the inability to provide feedback on skin textures.

Whilst efforts to restore tactile sensation in prosthetic limbs have seen significant progress in the past decade, the faculty to perceive temperature has been slower. “Temperature perception is among the last remaining hurdles to overcome for the comprehensive development of prosthesis that can genuinely mimic the sensations a biological limb offers” claims EPFL engineer Jonathan Muheim.

The research capitalised on past findings of the research group which stated that amputees often experienced temperature sensations in their missing hand corresponding to changes in temperature at certain spots on their remaining limbs. This happens due to the nerve stimulation originally meant for the missing hand. The team found that they could consistently induce these phantom temperature sensations over time in sixty-three percent of amputees.

For this new experiment, the team first mapped Fabrizio’s phantom temperature sensations to allow a spot on his arm to correspond with the equivalent sensation in the index finger of his missing hand. A temperature sensor was then attached to the end of his prosthetic hand's fingertip, which was connected through a controller to a device on Fabrizio’s arm, sending relevant temperature signals.

Despite the device currently using only one sensor at the index finger tip, the research team plans on incorporating more sensor-stimulator pairs to increase temperature sensitive spots on the hand. Parallelly, they are also planning to develop a prosthesis capable of sensing both touch and temperature. Shokur optimistically added, “Hopefully, we’ll reach that level in about a year.”

However, when multiple senses are combined, the speed at which the device communicates temperature may pose a challenge. In a paper revealed in Nature Biomedical Engineering last July, Osborn and colleagues developed a device as slender as a Band-Aid that conveyed cooling sensations nearly as quickly as natural reflexes.

Immediately, it is necessary for this novel device to be tested in larger groups and real-world situations to ensure it is unaffected by high temperatures or humidity. “We still need to perform those crash tests outside the lab” added Shokur.

When the device does leave the lab, Fabrizio already has a plan. “With these new technologies, I can better understand what I am touching” he stated in a pre-recorded video interview, “Without a doubt, my first priority would be to use it to cook in the kitchen.”