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One of the most exquisite¹ heat sensors³ in the world—it’s not in some government lab. It's in the head of a snake. The pit viper⁴, to be specific.

"They're incredibly sensitive. They beat any of the synthetic⁵ counterparts, even the most expensive semiconducting systems used in infrared⁷ or thermal⁸ cameras today." Chiara Daraio, a materials scientist at Caltech. "They can effectively resolve a few millikelvin of temperature changes at a distance of up to a meter." 

Now Daraio and her colleagues have designed a heat-sensing material that competes with the sensitivity of the snake. Using pectin. Same stuff you used to thicken jam. “Pectin, a double-stranded molecule⁹ ubiquitously present in the outer cell wall of plant cells, acts effectively as a tiny molecular¹⁰ temperature sensor²." When temperatures go up, she says, the double-stranded molecule unzips, "like the zipper¹¹ of a jacket."

So they did what you usually do with pectin—they made jelly, using pectin, water and calcium¹² ions. They dried that out, and got a thin, transparent¹³ film. Then, they had to test it. Which they realized they could do using a microwave and her son’s teddy bear. "Which can be heated up to a temperature of 37 degrees, roughly the temperature of a mouse or a running prey¹⁴ for a snake." 

And the pectin film was exquisitely¹⁵ sensitive to the warmed-up teddy bear—on par⁶ with the snake. The film could detect temperature changes as small as 10-thousandths of a degree celsius¹⁶. The study is in the journal Science Robotics. [Raffaele Di Giacomo et al., Biomimetic temperature-sensing layer for artificial skins]

Daraio says the skin could give robots superior sensing abilities. "Allowing for example robots to determine whether they're moving around inanimate objects, other robots, or even humans or animals, which are evidently warmer bodies." Or, she says, it could be used in sensitive skin on prosthetic limbs for humans. If we can figure out how to connect this artificial skin up to something far more complicated. The brain.

—Christopher Intagliata