3D Printing and Tomography

I inserted an extra syllable there, and even in my notes I had it spelled correctly. It's a marasium to forty one. So in other words, I I kind of pulled a classic Homer Simpson goof, like a Saxoma phone uh, several times in one episode. So thanks to Twitter user Ken Waldrop for pointing it out. It is incredibly embarrassing. It is all my mistake. It's totally me. It's kind of an insight into how Jonathan's brain works, which is

not all that great sometimes. I don't know why I inserted an extra syllable multiple times throughout that episode, but thank you Ken for letting me know, so that I could correct that error in this episode. Let's move on to another episode where I'm sure I will mispronounce multiple things. But it's a fascinating topic, or at least I find it fascinating. So I was looking through tech news recently and I saw a really interesting article. It was covered

in a lot of places. The first place I saw it was engadget, but I read about it elsewhere as well, and on engadget it has the title Researchers find a way to three D print whole objects in seconds. Now that immediately got my attention because typically three D printing takes a while, sometimes a long while to create an object, because it typically does it layer by layer. The answer

in this case lies in the technique called tomography. So this episode is going to cover a few different topics so that I can explain as best I can how this methodology works. So let's start talking first about just three D printing in general. It's a type of additive manufacturing, which means you're making something by adding to it rather

than taking unwanted stuff away. So with traditional sculpture, the sculptor might take a block of some material like marble and then carve it and cut away tons of it. There's an undoubtedly apocryphal quote attributed to Michaelangelo who allegedly described his process as you just chip away the stone that doesn't look like David. Now, Mikey probably never said that, but you get the point of the quote. You're removing material and whatever is left after you're done is the

finished piece. Additive manufacturing goes the opposite way. You add material bit by bit until you have the thing you wanted to make. So it's kind of like how potters work, you know, you add clay until you've got enough mass to shape it into whatever final form they have in mind.

And three D printers work in a similar way. They lay down thin layers of material one after another until layer by layer they have completed a print job, and typically the bottom surface would be whichever one is the largest of the finished three D object, So it might not necessarily be the bottom of the three D object, but the bottom of the print job, because a larger surface area means it's going to support the rest of that physical structure much more easily. There are three D printers.

They can work with all sorts of materials. The kind of average person would have access to. Uses plastic, one of two types, and a typical three D printer uses

spools of plastic cable as printing material. So the cable gets pulled into a piece called the extruder, which heats the plastic to make it sort of a semi liquid before depositing layers of this plastic, usually mixed with some sort of binding agent, onto the printing surface, or after the first layer, onto the last layer that was laid down.

This process tends to take a while, and you have to get the temperature and speed just right, or you get problems with layers not adhering to each other properly, or peeling away or sticking to the extruder as it moves through its path. I say this from experience. We have a three D printer in the office. We have successfully printed on it perhaps four times. We have run

it many more times than that. But however, it does me you can actually make whatever the object is relatively quickly compared to more traditional forms of manufacturing, and there are lots of benefits with three D printing. One is that it makes the prototyping process much faster. So let's say you got an idea for the body shape of a car. You could build a three D model of

the shape. Then you could use a three D printer to create a small physical model of what you had in mind, and you could test that and say a wind tunnel, to make sure it would work the way you planned before you moved further into the process. But maybe you discover that your design has some unexpected quality, like increased air resistance, so the extra drag would mean the car would not be as fuel efficient, so you

need to go back to the drawing board. You could go make some quick adjustments to your model and then send that to the printer again and print up a new prototype and would go pretty quickly. You don't have to carve away its stuff over and over, and another big benefit is that you have less waste overall. You're taking material and then only using a small part of

the overall mass and throwing the rest away. So lots of companies that manufacture physical goods use three D printing for the prototyping phase, and several are using three D printing in the actual manufacturing process for finished items, whether it's for a small component that goes into a bigger

product or a complete product from top to bottom. And while we've heard predictions that three D printing would bring about the end two mass manufacturing as we know it, the future in which everyone either has a three D printer or has easy access to a business that owns a three D printer. Thus far, that has not happened.

We have not seen a world where we all just print whatever we need on demand, where I sit there and think, oh, I need a new chair, so I'm gonna go down to the three D printers down the block and get one printed out. That has not yet happened. Maybe one day that will change, but for now the process isn't quite as convenient or as reliable as more traditional manufacturing methods. But that's traditional three D printers, and I've done episodes to go further into detail about their

history and how they work. So you can go and listen to those classic episodes if you want to hear more about that. But that's not what we're going to focus on for the rest of this episode. Now it's time to switch over to tomography, which is not the science of how tom works. It's that has nothing to do with tom and my space. Now, this relates to radiography and the use of stuff like X rays. Those we'll learn. It's not exclusively limited to X rays. And I know I've talked a lot about X rays in

recent episodes, but bear with me here. So early on, physicists learned about how X rays could penetrate solid material much more effectively than visible light could, and that if these X rays hit a sheet of photoreactive material, it would cause that material to react, so it reacted as if visible light had hit it. So if you put something like, I don't know your wife's hand between an X ray emitter and a sheet of photographic paper, you would end up with an image of your wife's skeletal

hand on that paper. I say wife because runt Jen Vilham run Jen, who discovered X rays, used his wife as a photographic subject for a lot of early X ray photographs, exposing her two ridiculous amounts of radiation in the process. At the time, he didn't know any better. But that's why I use that specific example. Now, why

do you get the skeleton hand in the finished image. Well, it's because X rays can pass through different materials with different levels of ease, so they can pass through less dense material more easily than the denser stuff, and that follows common logic. That just makes sense, right. So X rays can pass through muscle tissue far more readily than they can pass through bone, and bone is just much more dense. They can pass even less easily through something

like metal. So if you were to take an X ray photo of a typical person's hand, the bone would block more X rays from hitting the paper than the soft tissues would. The soft tissues would allow more X rays to come through. So the result is that the image on the photographic paper would be kind of like

a negative. The skeletal hand would show the spots on the paper where X rays were blocked from hitting it, and that meant that it would be relatively unexposed to light, and the softer tissues would allow it to go through, and thus you would have a greater exposure. So you can see that skeletal hand because the contrast between these two sections where the rays were blocked versus where they passed through. Now, the discovery of X rays came at

the very end of the nineteenth century. The medical establishment quickly saw the potential for this technology. They saw that this could be really valuable. You can see stuff like broken bones very easily. They immediately recognized its usefulness. They also over time recognized some of the dangers of X rays, such as radiation exposure, which was really more of a

problem for doctors than it was for patients. Patients would get small exposures whenever they would get an X ray done on them, but the doctors who were performing the X rays, we're getting exposures time and time again, and they were the ones who were really sorry to develop serious problems because X rays are a form of ionizing radiation, which means they can do cellular damage, and that in turn can manifest in different ways from radiation poisoning to

higher risk of contracting cancer. So uh, they also saw a limitation of this technology, namely that X ray photos have the same problem as any traditional photo has. They produced two dimensional images of three dimensional objects. So in medical schools, it was pretty standard practice for students to

work with or even produce cross sections of organs. Essentially involves cutting organs into thin slices like a loaf of bread, and then examining each of those slices carefully, and it's an effective way to teach medical students about anatomy and organ structures as well as learning what is and isn't typical, so that if one were to encounter an atypical scenario, the doctor would be able to recognize that as such. Now, if you put all the slices together, it looks like

the original organ. Of course, the big problem with this method is that it usually requires the original owner of that organ to be, you know, not alive anymore, making it a little difficult to apply medical knowledge to their case. So it's a useful educational tool, but not great for diagnosing a patient, at least not in a timely manner.

So doctors at the time were hopeful that there would be a new technology that would make it possible to create images of three dimensional objects in an accurate way, specifically organs showing their volume metric property, so that you could do things like look at them in perspective, as opposed to looking at what amounted to a series of silhouettes of organs and bones. If you took an X ray of someone's torso the rib cage would obscure a

lot of your your view. And then your lungs in your heart are located in an area where it's hard to see them individually because they're overlapping each other, so they wanted to find a way to create a three dimensional representation of this. Doctors at the time, we're hopeful that they could come up with a way of doing this in a practical manner, but they weren't really sure

how that would happen now. One person whose work would contribute to achieving this goal, though that was not his particular aim at the time, was a mathematician in the early twentieth century named Johann Raydon. In nineteen seventeen, Raydon produced a mathematical transform, a specifically an integral trans form, which means you add up basic elements until you get the full thing you're looking for. There are a lot of different versions of integral transforms, and he also discovered

its inverse. So this transform described mathematically a process that could be realized in a practical setting, namely that one could take the result of projections of an object and reconstruct an image in real space based on those projections.

It all has to do with geometry, and again into further detail would require someone far more educated in mathematics than i am, but there are some great videos online about the Radon transform that give it a good explanation of it, including one from Rich rad k It's titled d I P Lecture eighteen Reconstruction from Parallel Projections and

the Radon transform. You can find that on YouTube if you want to see a really detailed mathematical explanation of this that is far beyond what I can give you. Radon's work was interesting, but at the time there wasn't really any practical way to put it into actual use. One early step in getting to the goal was the development of linear tomography, or the ability to take radiographic images of a specific plane or cross section in a

solid object like a human being. So, in other words, you could create a cross section of a human being without having to cut the human being open. It was a miracle. So this relates to that mathematical transform I just mentioned, and interestingly, in the early days of tomography they that actually would predate Radon's transformers. Physicists were thinking about how to take X ray images from multiple angles to get a more complete picture of a specific internal

organ as early as nineteen fourteen. For actual implementations, there was a period from around nineteen twenty one to nineteen thirty four in which multiple people all working independently, all not knowing about each other, started to build systems capable of producing what would be called tomographic images. They didn't know about the other's work for a very long time, and when they found out. Can you guess what happened?

If your guess was, I bet they all rushed to be the one to claim credit for it, you'd be right, because that was a very human reaction to say I'm the reason why this works. But that was put on hold because a little thing called World War two happened.

The basic idea was the same from one instance to another instance that all these people were coming up with, but the actual details were different, such as the angles of motion for the X ray emitter and the detectors which would be on the opposite side of the patient, or the speed at which these components should move with

each other. Also, the word tomography itself was coined around nineteen thirty five and comes from the Greek word thomas, meaning section, and the suffix graphy from the Latin word graphia mean study of So it's the study of sections and it combines Greek and Latin. So I have friends who hate this word. They would say, stick with one or the other, um, one of them sitting right across

from me, but never mind that anyway. So imagine you've got a person standing in front of you, and you are somehow able to produce an image of a slice of that person from head to toe, and their shoulders are facing you. So it's like it's like you just are able to look at a slice of them right from the middle of that person, but you're able to do it without, you know, actually physically slicing them. So how does it work. Well, I'm gonna do my best to try and explain this process. So this is gonna

be an example. They don't all have to look this way, but this is a way for me to explain how this could happen. Imagine that we've got a patient laying down on an X ray table, and above this patient there is a track that's in an kind of like a rainbow above the patient, starting from around the head and ending somewhere around let's say the knees. Uh On this arc is mounted an X ray emitter, So this is the tube that will shoot out X rays at the patient. On the opposite side are X ray detectors.

This is underneath the table and the two can move with each other, So you start UH make moving the the emitter along this track. It moves gets in motion once it starts. Shortly after it started to move, it begins to emit X rays, and then it nears the end of its arc, it stops emitting X rays and then it comes to a physical stop. And you're aiming

this at a specific point on the patient. Perhaps you want to image this patient's liver, so you've aimed the emitter at the patient's liver, and as it goes through this entire arc, it still stays focused on a liver, so that point of focus does not change as it goes through this arc. UH. That liver will then become the pivot point for this particular scan. The ends of the seesaw of this pivot point would be the X ray tube on one side and the X ray receptors

on the other side. So if you think of a seesaw going up and down, in this case, it's not really going up and down, it's just going through an arc. Then one end of the seesaw is the emitter, the other end of the seesaw is the receiver, and the middle is the liver. The pivot point the The angle from the top of the arc to the bottom of the arc is called the tomographic angle. The angle at which the X ray emitter starts to admit X rays, and the angle at which are and when it stops

is called the exposure angles. There are two different angles in here. The exposure angle is always going to be smaller than the tomographic angle because of that. So how why why would you go through all this? What? What's the end result? I'll explain after we take a quick break. Okay, I just described this weird process of an X ray emitter going across an arc aimed at a patient. Why

would you do that? Well, it's because the image produced at the end of this process creates a very sharp picture of everything within the exposure angle along the focal plane of the pivot point. So let's say you're looking at this patient from the side the patient's laying on the table, you're off to an observation area off to the side. The focal plane is the horizontal slice of

that patient that runs through the pivot point. So let's say that you've determined that you wanted to aim at a point that's about eight centim ter's up from the surface of the table. That means that at that eight centimeters height along that entire horizontal slice of the patient, you're gonna get a very clear X ray image. The further out you are from the focal plane, so the further towards the patient's front or anterior and back or posterior,

then the fuzzier the image is going to be. Now, in this way, a radiologist could produce a sharp image of a specific slice inside a person. You would get that cross section, but you still have to deal with other issues, such as the fact that bone is more effective in blocking X rays than soft tissues or water.

So if the area you wanted to look at was below bone, such as within the rib cage, the bones would still present something of a problem, but you would still get a better look within a specific depth of a person, if that makes sense. So it was definitely an evolution of the science of radiology. Now you can repeat this process, and you could adjust the pivot location further up or further down to get sharp images along

different depths. But that also means you're also exposing the patient to multiple, you know, exposures of X ray radiation. A little exposure presents relatively low risk, but the more you're exposed to X rays, the greater the risk of adverse effects like damage to yourselves, right, so you want to be careful with this. Over time, advances in technology created the possibility of axial tomography, which was introduced in

the nineteen seventies. So in this version, instead of having an arc above the patient, the X ray emitter and receivers are mounted on a ring that goes around a table. So think of a table that passes through a ring and the patient lays on the table. The emitter and the receivers are mounted on opposite sides of this ring, and the patient and table are at the center of it.

And with axial tomography, you take a series of images with the X ray tube along different points of the ring, moving in a full circle around the patient it on the table, So you get above, below, and on either side and every angle you can really imagine, and the machines typically take a ton of quick images as the machine rotates around the table very very fast. You can actually find videos of a cat scan because this is

what this is a computer axial tomography scan. You can find videos of this equipment rotating where the cover is off so you can see how the internal structure rotates within this this machine. It's amazing how fast it goes. Uh I found it almost alarming how fast it goes, because these machines also are very big, and to think that something is spinning that fast around you is a

little unsettling. But the result of all this fuss is you get a cross section image of the subject, and the table can be moved further in or out of the ring, and another series of images can be taken, and that gives you another cross section, and you could do it again and take another cross section. You do this no off and you eventually end up with images, three dimensional images of the stuff you want to take pictures of, and you're able to put that together through

the help of computers. Engineers would call these CATS scans, and later just CT scans. A bit later, in the nineteen seventies, you had Dr Raymond Damedian who created a device capable of imaging internal body scans using magnetic resonance rather than X rays. The major benefit of this technology is that, unlike X rays, m r I machines do not emit ionizing radiation, so you don't get that radiation

damage to yourselves with an MRI machine. There are other damages if you are other dangers I should say, if you happen to have, you know, magnetic material on you, that's bad to be anywhere close to an m r I when it goes off, because you could stand to injure yourself or somebody else seriously, if they are in between the m r I machine and whatever it is you have on your body that is my metic or

you know, is ferromagnetic. Today, though, hospitals typically have both mr I machines and CT scanners because they're actually different reasons to use either one, like they're each good for different things. Uh. Over time, scientists and doctors have really refined the tech of CT scanners to really minimize the amount of ionizing radiation that patients will absorb, so they're they're pretty darn safe. So what does all this have

to do with three D printing? Well, in this case, tomography is all about creating a three dimensional object in real space using light and special photoreactive resins. It's super fascinating stuff which you probably can't tell just based on the words I'm using. So this reson I'm talking about is a type of photo polymer polymers are long chain molecules.

A typical polymer is a chain of similar building blocks linked together, and by building blocks, I mean monomers, and a monomer can either be a single atom or more frequently, it's a small group of atoms that form a molecule, so that's a monomer. A polymer is a chain of these monomers that are all chemically bound together in some way. So you can think of the chemical bindings as the link holding two elements together, and you get long, long,

long chains of these monomers to create polymers. A lot of polymers are artificial, including plastics. It's a common polymer we encounter in our day to day lines. But you can also find some natural polymers cotton, silk, cellulose, which is the stuff that woody plants are made out of, starches. These are all polymers, and proteins are polymers, right. Proteins are polymers that are created by chaining together amino acids.

Larger polymers are naturally heavier than smaller polymers. Makes sense. You've got more stuff, it's gonna have more weight. They also have higher viscosity, which means they resist flow as a liquid, So think of something like ketchup how it will resist flow. That's a high viscosty. Not that I'm saying that ketchups a polymer, but rather that it demonstrates high viscosity. Larger polymers also tend to have higher melting points and higher boiling points than shorter polymers they tend to.

Polymers can have all sorts of different manifestations and traits. So, for example, take starch and cellulose. Both of these natural polymers are made up of chains of glucose monomers, so at their core they're made of the same stuff. However, those chemical bonds between monitors are different between starches and cellulose, and that means that they have different h traits. Those differences are significant. So, for example, cellulose does not dissolve

in water. It's not digestible by human beings. Starch is dissolvable in water, and it is digestible by human beings. So even though they're both made of the same basic building blocks, the way those building blocks connect to each other changes there the way they manifest, the way they behave if you prefer so. All polymers have a chain of chemically bonded links, but some polymers have additional structures

attached to the links between those chain units. If those structures are complex, they're called pendant groups, kind of like a charm bracelet. Those pendant groups can affect how the polymer interacts with other stuff, and one of the things some pendent groups can do is link to pendent groups and other chains, so it can connect chains to each other. This is called cross linking, and cross linking makes polymers harder or more solid. Longer cross links are flexible, and

shorter cross links create a more stiff material. So they're all different types of polymers, and humans have made tons of different kinds and labs by changing different monomers together in different ways. And photopolymers are material that, as the name implies, react with light. The light changes the polymer's properties in some way, typically by causing it to go from liquid to solid, and sometimes it requires a specific frequency of light, like ultra violet light in order to

create this change. Sometimes it's not a frequency of light, it's a proper light intensity or absorption, but in any case, exposure to light causes the polymers to cross link, locking them together, solidifying them so you quickly go from a liquid material to a solid one. How quickly. Well, in the case of photopolymers developed by researchers at the Ecole Polytechnique Federal de Lausanne, and I know I butchered the pronunciation, it only takes a few seconds, and that's really darn fast.

And once the polymer's cross link they're locked in. They are not going to spontaneously let loose those links, so there's no danger of a solid object suddenly going curse bluche and turning into a liquid that's a technical term, curse bluche. Now, three D printing with photopolymers isn't a brand new thing. Some groups have been using processes involving light and photopolymers for a while, but most of those

have had limited resolution. Now, when we're talking about three D printing with resolution, we're talking about how fine you can get the details on a finished three D piece. A low resolution means you're not gonna have really any smooth edges or curved surfaces. It's kind of like building stuff out of standard lego bricks, so you can't make a smooth curve surface with those. You get this sort

of stair step effect instead. Earlier work, such as a project from the Lawrence Livermore National Laboratory, in collaboration with researchers from m I T, the University of Rochester, and UC Berkeley, would use multiple overlapping lasers projecting a holographic image into a vat of photopolymer us in. The three

lasers would each project into the vat from different angles. Collectively, they would create a three dimensional representation of the object, which would then take shape within the resin as it would start to harden into a solid. Now, the version I want to talk about is a little more advanced than that. I'll explain more in just a moment, but

first let's take another quick break. So, with a new approach out of Switzerland, the team wanted to create a virtual three D model of a small object and then turn that into a physical one. The system they built is capable of printing objects that are just a couple of centimeters in size, So they project an image of this object using a laser projector. The container that's holding the resin rotates at a pretty fast rate. Synchronized with

that rotation is the perspective of the three to mentional projection. So, in other words, imagine a rotating virtual representation of an object. Like a chess piece. So imagine like a night on a chessboard, and the night is rotating. It's it's a laser projection of it. That laser projection is rotating pretty quickly. It's rotating at the same rotational speed as a vat of liquid photo polymers, so that they're synchronized up with

each other. Now, all of this is supremely cool and awesome on its own, but here's the part that I think is truly astounding. The team has designed this process so that the resin doesn't receive enough light to solidify until the entire sequence of images and rotations is complete. So you can think of it as kind of like a slide show. Each slide represents a slightly different angle of this three dimensional object, and the resin only solidifies after the slide show has gone all the way through.

Because the resident requires a certain accumulation of light before those polymers cross link. The system actually is parceling out light. It's only giving enough light to start the process, but not complete it until every angle has been covered. At that point, there has been enough light intensity to cause the resin to solidify, which is genius. In addition, this

approach allows for much higher resolution print jobs. The process I described earlier with the multiple lasers, the one that was done by researchers from m I T and you see Berkeley and such that could print objects with a resolution of around three d microns. In articles I read about this new process, researchers were able to print a tiny replica two centimeter replica of Notre Dame cathedral with

a resolution of eighty microns. And just a reminder, you want a lower number here as it describes how small the edges are in curved surfaces. Technically it's a little bit more complicated than that, but you that's the easiest way to understand it. The team has created systems that allow printing in either hard or soft plastics, and they envisioned the process being used to print stuff for medical applications like three D printing artificial arteries, which is super cool.

The resident can be sealed in a sterilized container, so the finished printed product is safety use for medical applications because it hasn't been contaminated at all. It was created in a sterile environment. It was actually built that way. One drawback of this approach, at least for the near future, is the scale, because at the moment they're really limited to printing these objects that are just a couple of

centimeters in size. The team feels confident they can create a larger version of the system capable of printing stuff closer to fifteen centimeters in scale, but that's still fairly small. So you wouldn't be printing any fully formed furniture with this stuff, unless, of course it's for a really tiny playhouse or something. But it's still a really awesome some invention. And while it may not be possible to build something capable of constructing larger three dimensional objects right now, maybe

that will change down the line. If so, it would be an incredible advance and additive manufacturing. It would be cutting way back on the amount of time needed to produce an object. Uh. And the resin that isn't solidified can totally be used in future print jobs, so you don't have it go to waste, Like if you are making a small object and there's a lot of resin leftover, no worries, you can still use that in future jobs. That's pretty powerful. Now, As I said, this methodology owes

a lot tomography. It's essentially the reverse process in some ways. So rather than using these moving elements to image a physical object, it's using a reverse process to project a virtual image into a three dimensional volumetric space to create a physical object. Another area of research that relates to this and that it's an alternate take on three D printing is spearheaded by a guy named Adrian Bowyer, who

is the founder of a company called rep rap. Rap Rap refers to Bowuer's work in creating what he calls a replicating rapid prototyper, which is, in other words, a three D printer. He's now working on a really interesting application of science to create a new type of three D printer, one different from the tomographic approach I just described. So tomography is one way to scan a three dimensional object,

but Bowyer's research is looking into a different approach. He describes a scanning technology called spectra, which already exists, and it relies not on light or X rays as a scanning mechanism, but electric current. And here's how it works. Okay, you've got a three dimensional object you want to scan. So let's say it's a little clay garden gnome, and you put that inside a container that's already filled with an electrically conductive fluid, so current can flow through this liquid.

The gnome is now submerged in that liquid. The container also has little spot electrodes mounted on opposite sides of one another on the inside of the container, so they're pointed at each other. Uh the gnome is smack dab in between those two electrodes. These two electrodes can apply a difference of voltage, causing current to flow through the fluid. The solid object inside the fluid causes the current to move in different ways, and those fluctuations and current can

be monitored. Then you can rotate the electrodes slightly and repeat the process again, and then you rotate it and repeat it again. You do this many, many, many times, and the difference in how the electric current moves through the fluid can then be calculated and added up in an integral function that gives you a cross section of whatever it is you're skinning. So, in our case, the little clay garden gnome, and it's right along the plane

of those electrodes. So however high those electrodes are within the container, then you can move the electrodes up slightly. Let's say that you started at the very bottom of the container. You can move them up a smidge. Repeat this process and you build the next cross section layer of this little gnome this. Now you've got a virtual representation, and you do it again and again and again until

you had scanned the entire thing. Now, in practice, you would likely use a container that has lots of electrodes. You wouldn't just have to the whole thing would be have an insight coated with a grid of fine electrodes. You would only activate pairs of these at a time in order to get the scan. But by having them located around the inside of the container, you wouldn't have to rotate anything. You wouldn't have to have any moving parts. You would just activate pairs of electrodes to get those

measurements until you've got a full three dimensional scan. As I said, this technology already exists. That's a scanning technology. What Valuer wants to do is to take that model and reverse it much in the same way that the photopolymer resin approach I described earlier is like a reverse tomographic scan. So Buyer's method would use a monomer solution that polymerizes upon exposure to electric current. This is a

process called electro polymerization. It happens like there's some monomers that if you subject them to an electric current, they will form polymers and they'll solidify. So his ideas you take a virtual object. You've got a model, let's say it's a model of our little garden gnome, and you would apply current to a container holding monomer solution, and you would control the current in such a way so that it would activate only the bits of resin that

would represent that garden gnome in that volumetric space. So it's taking that scanning process completely in reverse. Now he hasn't managed to do it yet, but he's working on the problem. And Buyer's hope is to create a printer based on this methodology. And not only that, he's doing it in an open source approach. He's published all of his work on on his research in this method and

anyone interested in contributing can do so. And moreover, he has a goal to make sure that this process cannot be patented, so no person, no company, no other entity would be able to take this process and lock it away under intellectual property rights. So, in other words, if it works, it will work for everybody. And I think

that's pretty darn cool. Now, it may turn out that volumetric printing has inherent limitations that we cannot overcome, and in case that happens, it's still not a total loss because it's going to be incredibly useful for at least a certain number of applications, and we can still rely on other methods to produce things that are outside of that spectrum. That's pretty much the case with every single

process we can think of. Even with traditional three D printing, you're limited in the size of the thing you can print, at least in a single printing session, because you have to keep stuff at the right temperature. Uh. If it gets too heavy, then it can collapse in on itself.

So if you want to print a really big print job, you typically have to do it in sections and then glue the pieces together at the end or otherwise have them adhere to each other at the end, because uh, you just can't keep it structurally sound through the whole printing process if it's a really big print job. In the future, we could see three D volumetric printers making all sorts of stuff, including the basic scaffolding for things

like artificial and three D printed organs. In the meantime, I just think it's a super nifty technology to learn more about. As for other types of three D printing,

they are still really awesome. It has not proliferated quite to the level that people were predicting about five years ago, but the work continues and we've seen some really cool uses of the text so far, including enormous three D printers that can use stuff like a concrete based resin to build entire houses out of layer by layer, all the way down to students using commercial three D printers or even consumer three D printers to build stuff like

artificial limbs for people who otherwise would never be able to afford one. So it's truly a revolutionary technology. I can't wait to see where it goes next. And that wraps up this episode about three D printers and tomography. If you guys have suggestions for future topics of tech stuff, reach out to me. You can get in touch with me on social media on Facebook or Twitter. We use the handle text stuff hsw at both. Look forward to hearing from you, and I'll talk to you again really soon.

Text Stuff is a production of I Heart Radio's How Stuff Works. For more podcasts from my heart Radio, visit the i heart Radio app, Apple podcasts, or wherever you listen to your favorite shows.