Pulling 3D objects out of liquid, simplifying chemical synthesis, and Autodesk open sources its 3D printing feedstock

02 April 2015

3D printing anywhere but in heavy industry comes with a whole host of common complaints that have given it something of a negative reputation. Fabbed objects require additional detailing to get rid of the ridges and imperfetctions (true), you can't really print entirely hollow objects because internal structure has to be in place to support the upper surfaces (also true), a lot of hacks have to be done to the printer to make them more reliable (true... heated beds come to mind)... there are others but I'll spare the electrons. In fact, I think I'll cut to the chase and talk a little about a new fabrication technique from a startup that's just come out of stealth mode called Carbon 3D. Their technique is called CLIP (Continuous Liquid Interface Production) and it involves drawing solid objects upward from a pool of liquid feedstock. They've developed a resin which is sensitive to both atmospheric oxygen and ultraviolet light; UV causes the resin to solidify, oxygen prevents it from doing so. Using a membrane which has many of the properties of contact lenses that forms the bottom of the tank, UV light (probably from a chip laser) is shone upward into the underside of the surface of the resin. The layer of plastic, just a few times the diameter of a red blood cell in thickness, clings to the underside of a metal piston and is carefully pulled upward. The process is repeated thousands upon thousands of times until the finished object has been pulled free of the liquid feedstock tank and is ready to be cleaned off and dried. The technique is significantly faster than other plastic deposition methods - between 10 and 25 times faster in fact, which makes it suitable for industrial applications. Additionally, the CLIP technique can make truly hollow objects, from platonic solids to very complex three dimensional structures like models of the Eiffel Tower. I think Carbon 3D is really on to something here, and they're a company to keep a close eye on.

All but invisible to many today due to its ubiquity is the field of chemistry known as chemical synthesis, or constructing more complex compounds out of simpler ones. Nature does this quite handily - practically every living thing does this day in and day out at the cellular level but in the lab it tends to be a much more difficult process. Buying stockpiles of those simpler compounds is what most labs do but those simpler compounds have to come from someplace, which usually means synthesizing them from scratch. As one might imagine this tends to be significantly more tricky, not just due to the vagaries of synthetic chemistry in general but because it has to be done in industrial quantities and such processes tend to not scale well. So, the question becomes how to make creation of the basic compounds easier, or at least make them more widely available. At the Howard Hughes Medical Institute they've announced that they've figured out a way to rapidly and cheaply synthesize 14 different classes of precursor molecules in a paper in Science Magazine (paywalled). Information is kind of scant so a little digging is required but basically after analyzing the molecular structures of several thousand relatively simple compounds they found exploitable patterns that were automatable and parallelizable. The synthesis machine they constructed can crank out as much of those precursor compounds as they have raw materials for that can then be used for research in the biomedical and pharmaceutical research.

Since 3D printing first made it big a couple of years ago everybody and their backup seems to have gotten into the game, from scrappy open source startups to the big players in industrial manufacturing, including the CAD/CAM company Autodesk. Autodesk recently released a limited number of 3D printers that use liquid resin for feedstock called the Ember Explorer. Pretty straightforward, very polished, very expensive, special feedstock that you can't just jander down to the store and buy.. which, as one might imagine hurts uptake a little. Lock-in is good for profits but on the bleeding edge where rapid experimentation is the norm, if options are limited many will look to other solutions that are more readily available. So, it was with no shortage of interest that Autodesk opened the formula for the PR48, the liquid feedstock for their Ember series of fabbers. That's right, the formula for Polar Resin number 48 now carries a Creative Commons By Attribution/Share Alike v4.0 license, meaning that you can make it yourself (assuming that you have the know-how and access to the chemical precursors to do so), you can share it with whomever you want, however you want, and you can tinker with the formulation, but whatever is derived from or built on top of their work must be published under the same license.

And now, the formula for Polar Resin number 48. All percentages are weight to weight: