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I'm thrilled to be here tonight to share with you something we've been working on for over two years, and it's in the area of additive manufacturing, also known as 3D printing. You see this object here? It looks fairly simple, but it's quite complex at the same time. It's a set of concentric geodesic structures with linkages between each one. In its context, it is not manufacturable by traditional manufacturing techniques. It has a symmetry such that you can't injection mold it, and you can't even manufacture it through milling. This is a job for a 3D printer, but most 3D printers would take between three and 10 hours to fabricate it, and we're going to take the risk tonight to try to fabricate it on stage during this 10-minute talk. Wish us luck.
Now, 3D printing is actually a misnomer. It's actually 2D printing over and over again, and in fact it uses the technologies associated with 2D printing. Think about inkjet printing, where you lay down ink on a page to make letters, and then do that over and over again to build up a three-dimensional object. In microelectronics, they use something called lithography to do the same sort of thing to make the transistors and integrated circuits, building up a structure several times. These are all 2D printing technologies.
I'm a chemist and a materials scientist too, and my co-inventors are also materials scientists, one a chemist and one a physicist. We began to be interested in 3D printing, and very often, as you know, new ideas are simple connections between people with different experiences in different communities. That's our story.
We were inspired by the Terminator 2 scene with the T-1000, and we thought, why couldn't a 3D printer operate in this fashion, where an object arises out of a puddle in essentially real time, with essentially no waste, to make a great object? Okay, just like the movies. Could we be inspired by Hollywood and come up with ways to actually try to get this to work? That was our challenge, and our approach would be this: if we could do this, we could fundamentally address the three issues holding back 3D printing from being a manufacturing process. One, 3D printing takes forever. There are mushrooms that grow faster than 3D-printed parts. Two, the layer-by-layer process leads to defects in mechanical properties. Three, if we could grow continuously, we could eliminate those defects. In fact, if we could go really fast, we could also start using materials that are self-curing, and we could have amazing properties. So if we could pull this off and imitate Hollywood, we could in fact address 3D manufacturing.
Our approach is to use some standard knowledge of polymer chemistry to harness light and oxygen to grow parts continuously. Light and oxygen work in different ways. Light can take a resin and convert it to a solid, converting a liquid to a solid. Oxygen inhibits that process. So light and oxygen are polar opposites from one another from a chemical point of view, and if we can control light and oxygen spatially, we could control this process. We refer to this as CLIP. It has three functional components. One, it has a reservoir that holds the puddle, just like the T-1000. At the bottom of the reservoir is a special window, which I'll come back to. In addition, it has a stage that will lower into the puddle and pull the object out of the liquid. The third component is a digital light projection system underneath the reservoir, illuminating with light in the ultraviolet region.
The key is that this window in the bottom of the reservoir is a composite. It's a very special window. It's not only transparent to light but permeable to oxygen. It has characteristics like a contact lens. So we can see how the process works. In a traditional process with an oxygen-impermeable window, you make a two-dimensional pattern and end up gluing it onto the window. In order to introduce the next layer, you have to separate it, introduce new resin, reposition it, and do this process over and over again. But with our very special window, oxygen comes through the bottom, and as light hits it, that oxygen inhibits the reaction and forms a dead zone. This dead zone is on the order of tens of microns thick, so that's two or three diameters of a red blood cell, right at the window interface. That remains a liquid, and we pull this object up. As we discussed in the science paper, as we change the oxygen content, we can change the dead zone thickness. So we have a number of key variables that we control: oxygen content, the light, the light intensity, the dose to cure, the viscosity, and the geometry. We use very sophisticated software to control this process.
The result is pretty staggering. It's 25 to 100 times faster than traditional 3D printers, which is game-changing. In addition, as our ability to deliver liquid to that interface improves, we can go a thousand times faster, I believe. That in fact opens up the opportunity for generating a lot of heat, and as a chemical engineer I get very excited about heat transfer and the idea that we might one day have water-cooled 3D printers because they're going so fast. In addition, because we're growing things, we eliminate the layers, and the parts are monolithic. You don't see the surface structure. You have molecularly smooth surfaces. The mechanical properties of most parts made in a 3D printer are notorious for depending on the orientation in which you printed them, because of the layer-like structure. But when you grow objects like this, the properties are invariant with the print direction. These look like injection-molded parts, which is very different from traditional 3D manufacturing.
In addition, we're able to throw the entire polymer chemistry textbook at this, and we're able to design chemistries that give rise to the properties you really want in a 3D-printed object. There it is. That's great. You always take the risk that something like this won't work on stage. But we can have materials with great mechanical properties for the first time. We can have elastomers with high elasticity or high damping. Think about vibration control or great sneakers, for example. We can make materials with incredible strength, a high strength-to-weight ratio, really strong materials, and really great elastomers. So throw that in the audience there. Great material properties.
The opportunity now is that if you make a part that has the properties to be a final part, and you do it at game-changing speeds, you can actually transform manufacturing. Right now in manufacturing, there is a so-called digital thread. In digital manufacturing, we go from a CAD drawing, a design, to a prototype to manufacturing. Often the digital thread is broken right at prototyping, because you can't go all the way to manufacturing when most parts don't have the properties to be a final part. We can now connect the digital thread all the way from design to prototyping to manufacturing. That opportunity opens up all sorts of things, from more fuel-efficient cars, to great lattice properties with high strength-to-weight ratios, to new turbine blades, all sorts of wonderful things. Think about needing a stent in an emergency situation. Instead of the doctor pulling a stent off the shelf, a standard size, you'd have a stent designed for you, for your own anatomy, with your own tributaries, printed in real time in an emergency situation, with properties such that it could dissolve away after 18 months. Really game-changing. Or digital dentistry, making these kinds of structures even while you're in the dentist's chair.
Look at the structures my students are making at the University of North Carolina. These are amazing microscale structures. The world is really good at nanofabrication. Moore's law has driven things from 10 microns and below, and we're really good at that. But it's actually very hard to make things from 10 microns to a thousand microns, the mesoscale. Subtractive techniques from the silicon industry can't do that very well. You can't etch wafers that well. But this process is so gentle that we can grow these objects up from the bottom using additive manufacturing and make amazing things in tens of seconds, opening up new sensor technologies, new drug delivery techniques, new lab-on-a-chip applications. Really game-changing stuff.
So the opportunity of making a part in real time that has the properties to be a final part really opens up 3D manufacturing. For us this is very exciting, because this really is owning the intersection between hardware, software, and molecular science. I can't wait to see what designers and engineers around the world are going to be able to do with this great tool. Thanks for listening.