What if, instead of going to the store to buy a new toilet brush, all you had to do was walk into your office nook and print out a new one? Not a picture of a toilet brush, cause why would you want that, but an actual toilet brush, that you can use to clean those hard to clean stubborn stains in your toilet. I know, your toilet is very dirty.

"Nah," you'd probably say, "by the time that's possible we'll have robots to clean our toilets for us. And it'll be freeeee."

Well, printing 3-dimensional stuff in the comfort of your own home might be a reality sooner than you think. 3D printing, the process of creating solid 3-dimensional objects just by hitting print on a computer is already happening. Actually it's been happening for like thirty years. But recently, it's become inexpensive enough to take seriously as a technology that could change the future of stuff. Like right now you could go online and for a couple thousand dollars or less buy a machine that will make you a pretty sweet Pez dispenser with your face on it. Who wouldn't want that?

And 3D printing may not only change the way we make stuff to clean our toilets and pop candy in our faces, it also has big implications for the manufacture of drugs, food, prosthetics, and even human tissues by which I mean: in the future you might even be able to print yourself out a new kidney. Kinda puts the robot with the toilet brush to shame, doesn't it?

[intro music]

People have been making stuff for a long time. Tools, jewelry, kitchen wares, clothing, religious icons, ... Here is the thing: historically, if you were going to craft an object, say, a spear for hunting woolly mammoths, most of the time you just take a stick and a rock and then whittle away at both of them until you have a straight stick and a spear point that's sharp enough to put the herd on a big hairy elephant. Then you tie them together with rabbit guts or something. This process of manufacturing objects by removing pieces from a chuck of material is called a subtractive process and it's how we've always made stuff because that's the technology we had.

3D printing, instead of taking material away, builds an object from the bottom up in an additive process. It's like making the spear to kill the woolly mammoth by laying down one layer of wood and stone and rabbit guts at a time. Basically a 3D printer turns data into an object. It uses software like you'd find in a normal paper printer, only instead of creating a two-dimensional image, it's three, and instead of laying down layers of ink, it squirts out whatever material you want: plastic, metal, synthetic resin, concrete, ... even sugar. Once the first layer is dry or primed with a laser, another layer is squeezed out on top of it, and then another and another, until a whole object is made. A doorknob, a lamp, a handbag, a dental crown, ...

3D printing has been around almost as long as ink-jet printing, which was invented in the mid 1970s, but it was in 1986 that the first 3D printer was sold. The 'stereolithography apparatus' or SLA was used to make models of machine parts and such from layers of liquid plastic that were cured with the UV-laser. By the mid 1990s other materials and methods were used: powders of different kinds of plastics, various lasers, ... And while people saw a lot of potential in the technology, for a long time the only real use anybody could find for it was like making models, like architects' models of buildings. But technology has made it possible to print increasingly sophisticated objects all in a single go, which is why 3D printing could change manufacturing, engineering, and the ways in which we practice science, especially medicine.

For starters 3D printing allows us to customize things that used to be only manufactured in bulk. For example, prosthetic limbs used to be made en masse, and they were basically all the same. There was like small, medium, and large, and left and right limbs, but each one had to be customized to a patient after they were made. With 3D printing, prosthetics are being built to order, with each individual patient's specifications.

Another new innovation is that objects can now be printed with moving parts. This is made possible by laying down a dissolvable support material between the moving pieces that can be rinsed off once the object is made. So if you're making a series of gears that move together, the 3D printer might lay down a gel or powder between them so the individual pieces don't fuse together. But once it's done you can dissolve away the support material and your printed moving parts are ready to go. That means a prosthetic leg can now be made with flexible features to make it more closely resemble a human leg: locking knees, jointed toes, flexible ankles, ...

In addition to making bigger, more complicated things, we're also discovering how to print the very small. Like, very small. Like chemicals. Chemists have figured out how to print objects as small as two hundred and eighty five micrometers: smaller than a grain of sand. Since most drugs are made up of carbon, oxygen, and hydrogen, we may soon be able to build drugs using organic molecules as ink. Trillions of these printed molecules can fit together to create a drug that would do exactly what it's intended to do in the body because all the atoms are arranged just so. Already a team at the University of Glasgow has figured out how to print Ibuprofen, the pain killer, from scratch.

But it gets weirder!

The next step is bio-printing animal tissue. Let's start out with raw meat. You know, for eating. The idea here is the same as any other form of additive manufacturing: you got a printer, some data, and the material, but in this case the material is living cells. Stem cells are able to replicate themselves in culture over and over, so once you've extracted enough of them from a donor animal they can form a 'bio-ink', they call it ink, that can be put in a 3D printer cartridge and layered in the form of a piece of meat. Those cells then fuse together and form tissue. Yummy! A piece of steak! That never mooed!

I know what you're thinking, because of course you're thinking it because you're not stupid: if they can make a piece of meat, they can make a person. Because what is a person but a very complicated piece of meat? Well... it's a very complicated piece of meat. Very complicated. Whole networks of organ systems and nerves and veins and what-not. Plus, meat is post-mortem tissue, and something that's dead is a lot easier to create than something that's ALIVE, as doctor Frankenstein learned. All we require of meat is that it looks and tastes like it once was alive.

But even though we're not at the point where we can print a living organism, bio-engineering live animal tissue using 3D printing technology is definitely happening. Human stem cells have already been used to produce bits of relatively simple tissue, like cartilage and bone. Meanwhile, researchers at Cornell University are working tirelessly to give us bio-printed human ears, and others at Wake Forest University are developing skin that can be printed directly onto burned flesh.

Because of research like this some scientists say bio-printing is the future of organ transplants. Today, if you need a kidney or a heart, you have to wait till somebody else's becomes available, and then once you get one there is a lot that could go wrong. Your body, for instance, could reject the new organ altogether. But 3D printers might soon be able to manufacture made-to-order replacement organs, customized for each person from a mixture of embryonic stem cells, and the patient's own adult stem cells. The difference, by the way, between adult stem cells and embryonic stem cells is that, while adult stem cells can replicate themselves in the body to replace dying cells and regenerate damaged tissue, embryonic stem cells are pluripotent, meaning that they can become almost any type of cell in the body. Adult stem cells are also more difficult to track down in the body, while embryonic stem cells can be cultured in a lab from an existing line or group of cells. They're not actually taken from embryos each time they're needed.

But while building bio-printed body parts may be possible in the near-ish future, researchers have encountered a few stubborn obstacles. Like for example that printing with embryonic stem cells is difficult because they're very delicate. While adult stem cells might make sturdy enough ink to print hamburgers with, it's proved tougher to squeeze embryonic stem cells out of a toner cartridge and expect them to survive. Though it has been done. Also some animal tissue is much more complicated than others, for instance we'll probably see printed cartilage used in medical procedures before anything else because it doesn't have a lot of internal structure vascularization. Once they've got the cartilage down they might move on to bone or even liver.

And finally, obviously there's a big problem with connecting the bio-printed tissue to the real tissue. Like how do you hitch that stuff up to blood vessels to get oxygen? That's the biggest problem facing bio-printing at the moment. However, researchers envision a time when any healthy person could go into a doctor's office and get a full MRI scan that would record the geometry of their whole body, and then that information could be kept on file. If you hurt your knee and needed new cartilage, or if you needed a whole new heart, they can harvest some stem cells from your body, incubate them, and then use those cells mixed with embryonic stem cells as filler to re-fabricate whatever part of your body needed to be replaced.

3D printed stem cells could even be used to make human tissue models for drug testing, effectively eliminating the need for animal testing. So 3D is the future. Creepy future? Maybe, but the future nonetheless. Either way you're getting a new toilet brush.

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