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  • It's basically right out of a spy movie: a glider swoops into enemy territory at night,

  • lands with some sort of secret message or item, and then vanishes without a trace in

  • the pink light of dawn.

  • Now where did this come from?”

  • our unwitting villain says, bending down to pick it up

  • Okay, okay, I might be getting overexcited.

  • But as of this week, a disappearing plane could really exist.

  • At a meeting of the American Chemical Society, researchers announced that they have created

  • a material that vaporizes in sunlight.

  • It's all thanks to the incredible power of chemistry.

  • The material is a polymer known as polyphthalaldehyde or PPHA.

  • Polymers are like chains.

  • They're big molecules made up of many repeated smaller units chemically bonded together.

  • Each link in the chain is held together by one or more chemical bonds, and under the

  • right circumstances, those bonds start to come apart and the whole chain can disintegrate.

  • But when that happens is dependent on the particular polymer and what's known as its ceiling temperature.

  • Below that, the polymer wants to stay a polymer.

  • Above it, it will start to break down into its component pieces, called monomers.

  • For instance, good old polystyrenesometimes known as Styrofoamhas a very high ceiling temperature.

  • Which is why the stuff hangs around in landfills basically forever.

  • PPHA has a low ceiling temperature.

  • You break one bond at room temperature and the whole thing breaks down almost instantly.

  • So the challenging part is actually keeping it from vanishing before you want it to.

  • Luckily, the research team found a way to remove more of the catalyst that helps build

  • the polymer in the first place, which gives it a much longer shelf life.

  • They also used a cyclic version of PPHA rather than a linear one, which is more stable because

  • it doesn't have any loose ends where the unraveling process can start.

  • And thenthey just started experimenting.

  • They added a light-sensitive compound to it to get it to start the self-destruction process on cue.

  • It produces a strong acid when it encounters UV light, which then attacks the polymer's bonds.

  • Once one bond breaks, the PPHA has loose ends again and disintegrates in 5 to 7 minutes

  • as long as the ambient temperature is above PPHA's ceiling temperature of -40˚C

  • Then they found photosensitive catalysts that worked at different wavelengths of light,

  • so that indoor light or different colors could be used to trigger the self-destruct.

  • And they added a liquid plasticizer to the material, so that they could have both rigid

  • and bendy structures to build things with, like, planes and parachutes.

  • They even built in a time-delay function.

  • By having the catalyst produce a weaker acid, they found they could have a longer gap between

  • light exposure and when the structure self-destructs.

  • And they're not done yet!

  • While PPHA itself vaporizes completely, the plasticizer does leave behind a liquid residue,

  • so that's something the team is working on solving.

  • The researchers also hope that the materials can be used for all sorts of purposes in the

  • future, like no-waste sensors for environmental monitoring.

  • So they're going to keep tinkering to see what other kinds of special features they

  • can build into their PPHA.

  • Speaking of things that sound made up by Hollywood, scientists can apparently doll out night vision now.

  • Using nanoparticles!

  • Injected into your eyes!

  • Well, not your eyes.

  • Not quite yet.

  • But scientists have given infrared supervision to mice, and according to a talk they gave

  • at the American Chemical Society meeting this week, they are interested in doing it with

  • other mammals and maybe, someday, with people.

  • Without night-vision goggles, mammals can only see light in what's known as the visible

  • spectrumwavelengths of about 400 to 700 nanometers.

  • Near-infrared light is beyond the red end of the spectrum.

  • And it's what night-vision goggles that use thermal imaging look for, because it's

  • emitted by warm objects.

  • That means that if we could see it, it would let us see things that give off heat even in total darkness.

  • So, to make infrared light visible to us, the researchers developed specialized nanoparticles

  • known as upconversion nanoparticles or UCNPs, which had a core made mostly of the rare-earth

  • elements erbium and ytterbium.

  • When these elements absorb infrared light, they emit visible green light, basically converting

  • the invisible light into something mammalian brains can make sense of.

  • The team got these nanoparticles to stick to light-sensing cells by adding a protein

  • that attaches to certain sugars.

  • Then, all they had to do was inject the nanoparticles into the eyes of their mouse test subjects.

  • Ten weeks later, the mice weren't just finethey could see near-infrared light.

  • For example, mice trained to expect a shock when they saw green light would also freeze

  • when they saw infrared light because the nanoparticles were converting it to green light inside of their eyeballs.

  • And in a swimming task, mice with the infrared vision were able to locate a platform they

  • could stand on in the dark.

  • Mice without the UCNPs couldn't find it.

  • Now, exciting as all that is, we're probably still a ways away from injecting this stuff

  • into human retinas.

  • But!

  • The researchers have made steps towards making them more human-friendly, including finding

  • an organic substitution for the rare-earth elements in the UCNPs.

  • These don't only make the nanoparticles a bit more biocompatible, they also improve

  • the tech by making the transformed light brighter.

  • And in addition to basically giving people superpowers, the researchers also imagine

  • the tech being used to deliver infrared-triggered doses of medication directly to the photoreceptors of the eye.

  • But there are a lot of regulatory hurdles that would need to be cleared before we get there.

  • For now, I guess we'll all just have to be jealous of these mice.

  • It's like maybe the one time being our favorite lab animals has really paid off for them,

  • solet's let them have this one.

  • Thanks for watching this episode of SciShow News!

  • And especially thank you to today's President of Space, Matthew Brant.

  • Matthew, we really appreciate your continued support!

  • In fact, here's a special space salute!

  • And thank you to all our other patrons, too.

  • If you're not one of those people, but you think what we do on this channel is pretty

  • great and want to help us keep doing it, you can learn more about becoming one of our patrons at Patreon.com/SciShow.

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