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Regaining One’s Sense of Touch: Advancements in Prosthetic

Author: Joanna Xu

Editors: Rachel Chen, Viola Chen

Artist: Kevin Lin

Car collisions falls, and transportation injuries leave millions worldwide in need of amputated limbs each year. According to a survey that assessed the prevalence of amputations due to trauma, 57.7 million people were living with a limb amputation globally. Amongst these amputees, a significant number of them were aged 18-64, suggesting that most of them were young enough to have needed to resume working after sustaining these injuries. This can be extremely frustrating for amputees with a prosthetic arm or leg. Even though they eventually learn to use these replacements, they will always be metal attachments instead of their natural limbs. Although the typical amputee can move their arm whichever way they want, quite similar to the human arm, the prosthetic does contribute to their sense of touch. They can no longer feel temperature or texture through that limb. This can put the lives of amputees in danger when they are unable to feel danger approaching. Even if there is no danger, being unable to feel the outside temperature or the warmth of a loved one is undesirable to all. 

Researchers and engineers have been working for years to find a possible solution to this issue. Recently, a brand has come out with the MiniTouch, a two-piece attachment that allows amputees to feel the temperature of objects. Designed by researchers at the Swiss Federal Institute of Technology Lausanne and the School of Advanced Studies Sant'Anna in Pisa, the gadget results from years of hard work. In previous studies by the team, they found that by putting thermal electrodes on the residual limbs of the amputees and then stimulating them by touching objects of varying temperatures with a sensor, the subjects felt that they were experiencing the temperature through their prosthetics. This was the introduction to phantom thermal sensation. When a patch of skin on the amputee's remaining limb is stimulated, it sends signals through a pathway to the brain. Although these signals would ordinarily be sent from the hand or fingertips, it was surprisingly discovered that they could be produced even without the missing limb. After more research, the team found that these phantom thermal sensations were produced in different areas of the missing limbs, depending on the subject. This confirmed that the nerves cut off during amputation were still present in the arm’s skin. These discoveries set the stage for the development of the Mini-Touch device.

The finished product consists of a thermal sensor and a thermal stimulator. The thermal sensor is located on the index finger of the prosthetic arm, actively measuring the temperature of any object that may come into contact with the user’s hand. Once in contact, the sensor generates the signal and sends it to the thermal stimulator. The thermal stimulator is installed into the socket that secures the prosthetic to the remaining limb, ensuring that it touches the point of stimulation. The point of stimulation is the area on the residual limb that, when stimulated, allows the amputee to feel as if they are truly feeling the object's temperature through their prosthetic arm. 

The Mini-Touch has already helped many individuals regain their sense of connectivity with the world around them. Now that they can feel temperature with their prosthetics, there is a greater sense that the artificial limb is truly a part of their body. Amputees can safely pick up everyday chores, such as cooking, without fear of touching anything too hot or cold. They can feel the cold metal bars or the chill of holding an iced latte—all the feelings the typical person doesn’t think about. These feelings, despite how common or negligent non-amputees find them to be, could not be felt by those who had lost an arm. Now, with the Mini-Touch, they can be more in touch with the world surrounding them. Another important benefit is the bond between loved ones. Many amputees have not felt the warmth of their loved one’s hand in theirs, a cherished feeling for many. The Mini-Touch allows them to experience such sensations.

This device has paved the way for all future prosthetics, allowing amputees to regain their sense of touch. There is the possibility of this technology being applied to several different parts of the body, whether it be the legs or other body parts. Researchers could even go on to find some way to help amputees feel the texture or at least make them feel like they can distinguish textures from one another. Ultimately, this invention will go on to help millions of amputees worldwide and even help future amputees feel more confident about their ability to live their lives normally after amputation. 

 

Citations:

McDonald, Cody L, et al. “Global prevalence of traumatic non-fatal limb amputation.”

Prosthetics & Orthotics International, vol. 45, no. 2, 4 Dec. 2020, pp. 105–114,

 Administration, Web. “Limb Loss Statistics.” Amputee Coalition, 1 Aug. 2017, www.amputee-

coalition.org/resources/limb-loss-statistics/.   

Sabelli, Chiara. “A Prosthetic Hand That Feels the Heat.” Nature News, Nature Publishing

Magazine, Smithsonian. “In a First, a Prosthetic Limb Can Sense Temperature like a Living

Hand.” Smithsonian.Com, Smithsonian Institution, 9 Feb. 2024,

www.smithsonianmag.com/science-nature/in-a-first-a-prosthetic-limb-can-sense-

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