Touch something sharp, and that’s our reaction: ouch – and we move our hand away.
Now you might think that building a prosthetic hand would be a chance to put an end to “ouch”. And if you were Tony Stark (Iron Man, if you’ve not looked into the Marvel universe for some time), that might be right.
But the latest news in the world of prosthetics, is that scientists at Johns Hopkins University have developed an “e-skin” that lets a person with a prosthetic hand feel pain. And outside the world of superheroes – that news is good news.
“After many years, I felt my hand, as if a hollow shell got filled with life again.” That’s how one man, an amputee, described it – after using testing a prosthetic hand with the new e-skin.
What most of us take for granted, that we can feel what we touch – has not been true for anyone with a prosthetic hand. What that person often wanted, was a hand as close to a flesh-and-blood hand as possible. A hand that can feel as much as possible, including feeling pain.
A sense of touch is also a practical matter. Pain is a signal. It tells us that something is harmful — too sharp or hot, for instance. And how something feels in our hand also tells us – be gentle, because we are holding something delicate; or squeeze tight, because this is slippery or heavy to hold.
So, how does this e-skin work? Made of fabric and rubber, with layers of sensors (for this experimental e-skin, the sensors were designed to respond to the curvature of an object and its sharpness), it was modelled on human skin. Not the look of our skin, but the function of our skin. And this e-skin, is made to be “pulled over” a prosthetic hand.
It works, because where we “feel” pain is not in our hands, but in our brains. So an electronic skin, with sensors that respond to a physical touch (including the sensation of something sharp, that causes pain) – when the e-skin sends that information to the brain, the brain “feels” pain.
“I can differentiate between pain and not-pain without thinking, instinctively knowing if my arm is in danger,” another volunteer reported to the study’s author.
Turns out there’s another practical benefit to that. Prosthetics are expensive, and unlike flesh-and-blood, if they are damaged, they can’t heal themselves. So being able to feel pain, means knowing when to drop something, or pull away from something that’s dangerous – as opposed to inadvertently wrecking an expensive prosthesis (it happens).
And the scientific advances that make a miracle like this possible – a prosthetic hand which allows the person wearing it to feel, even to feel pain – are made possible in part by another advance, the advanced materials that we keep developing from petrochemicals.
Oh, and speaking of Iron Man, this electronic skin could also be useful in building better robots – because it could give them a more delicate, human-like touch. So you can turn C3PO loose in the kitchen, without worrying that the kitchen will burn him.
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