3D printing has revolutionized the way we make stuff. And the technology is evolving - fast! Advances in 3D printing have made it possible to print things we never could before - like tiny batteries and super effective water filters. And we might even be able to use 3D printing to colonize other worlds, starting with the Moon. 

3D printing is sometimes known as additive manufacturing, which should give you some idea of how it works: You program a 3D printer with a design, and it builds a thing according to that design, generally by stacking layers of material on top of each other. But one problem that's come up is that it's hard to 3D print on a small scale. If you're printing something that's, say 5 hundredths of a millimeter wide, every fraction of a millimeter counts.

But 3D printers are getting more precise all the time. In 2013, a team of American researchers managed to 3D print extra-efficient batteries the size of a grain of sand. To make their miniature batteries, the team created a special kind of ink with lithium-ion nanoparticles in it. If that sounds familiar to you, it's because lithium-ion batteries are in almost everything you use, from your smartphone to your hybrid car. And like all batteries, they work using electrodes and an electrolyte. A current passes between the electrodes by flowing through the electrolyte, providing electrical power. 

So engineers used that special ink in a custom-made 3D printer, which printed stacks of electrodes, each thinner than a human hair. Then they put the stacks in an electrolyte solution, to provide a medium for the current to pass through. And that was it! They had a very tiny battery, that turned out to be just as efficient as the kind you can but at the store. These new nano-printed batteries may soon wind up in microscopic technologies, like miniature cameras, tiny medical implants, and adorable little nanobots. 

Another new invention that only exists because of 3D printing? Better water filters. Water filters use membranes that trap particles you don't want, along with potentially dangerous microbes. The problem is, most membranes get clogged up pretty easily. But in 2014, a company in Singapore developed a 3D printed membrane using an ink made out of titanium dioxide, which develops the ability to kill microbes when it's exposed to UV light, like from the Sun. So when the water passes through the UV-exposed membrane, any dangerous microbes die. And the membrane also breaks down organic compounds, so they don't stick around and clog it up. 

So scientists are using 3D printing to develop all kinds of new ideas here on Earth. But it's also helping us explore space. In fact, there's a 3D printer on the International Space Station right now! And in 2014, astronauts used it to 3D print objects in space for the first time ever. Most common objects are printed out of a kind of plastic, often referred to as resin. And NASA engineers wanted to see if things like tools could be printed in space - if so, crew members could print whatever they needed on the fly.

But researchers weren't sure if weightlessness would affect the strength of resin. So the ISS crew conducted a test, and printed an ordinary ratchet wrench and 19 other objects, like containers and spare parts, on board the station. When the stuff they printed was sent back to Earth for testing, researchers found that the plastic was as strong as plastic 3D printed here on the ground. Which means 3D printing can be used on the space station and on future long-term missions, allowing crew members to print any replacement parts they needed.

And speaking of long-term missions: the European Space Agency is planning to use 3D printing to help build a colony on the Moon. Their plan - which is still in the very earliest stages - is to first send robots to the Moon to collect raw material: the lunar regolith, aka the Moon rocks. Then, giant 3D printers would be sent to use the regolith to make things like tools and even entire buildings. It might sound like something out of a science fiction novel, but researchers are already developing designs for printable structures that would protect against radiation and small meteoroids. To prove that it's possible, they've already printed a 1.5 metric ton building block made synthetic regolith. So the first Moon colonists might live and work... in a 3D printed town! 

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