Field Enhanced 3D Composite Printer

3D printers are now surprisingly cheap. I 3D printed a pencil holder while doing work experience at a nuclear engineering company back in the late 90's and was told it probably cost $30,000, if it weren't a "training/calibration exercise". Now, 3D printers cost about as much as 2D printers, and are hilariously cheaper to run.

I got one myself, it works like this: At the bottom there is an LCD screen, similar to the one you're looking at, only monochrome - black and white if you will. Instead of white however, the screen allows UV* light to pass through forming any image you like. Above the screen is a bath of goo. When exposed to the UV image, the goo stops being goo and starts being plastic. So far, you can make a 2D plastic shape.

The 3D part is where the build platform** comes in. The platform is a solid lump of flat aluminum that begins ~0.1mm from the screen with ~0.1mm of goo between it and the screen surface, then when the first UV image is formed, the goo polymerizes on the surface of the platform. The platform moves up 0.1mm and the process repeats until your shape emerges from the goo, upside down attached to the platform. Lovely. What more can we need? Well, the plastic formed is just plastic, it has great properties, like corrosion resistance, flexibility etc. but add in reinforcement like glass or carbon fiber and you create a composite material. These can be made with extraordinary properties, huge strength-to-weight ratios, complex shapes and the reinforcement material can be selectively arranged to provide rigidity/flexibility in specific directions & areas.

A common composite you might find in a typical power tool, usually nylon with ~30% glass fiber reinforcement. These parts are injection molded with short glass fibers randomly distributed in the molten plastic. There's no control of the fiber orientation, because the part is molded all in one go. More sophisticated components, like in F1 cars or aircraft, lay sheets of woven fiber, usually by hand, and carefully control orientation in that manner. But what can we do with the 3D printer?

So, take glass/carbon fibers and modify them to have a +ve end and a -ve end. In something like artificial spider's silk, this already an inherent property, one end is a carboxylic acid that loses a proton to become -ve, the other end is an amine that gains a proton to become +ve and the whole molecule is net 0 charge, but will happily align itself with an electric field.

Now, in our 3D printer we have goo, containing randomly arranged fibers with +ve/-ve ends. Now, just before we turn on the UV light to polymerize the plastic, we apply an electric field across say, the x axis. All the fibers line up and then you turn on the light. Now the reinforcement is aligned, and better yet, you get control of the orientation in 0.1mm steps. If you only align in the x axis, your part will be stiff in that direction, and as flexible as the base plastic in the y&z axes. Now you have complete control, you may even be able to "knit" the fibers, making a continuous x,y,z mesh.

Possible problems: I don't know how hard it is to make glass/carbon fibers with +ve/-ve ends with net 0 charge. It would be easy to purify them however, apply an electric field and the net -ve will migrate to one electrode and net +ve to the other. I'm not sure how electric fields work in relatively non-conductive hydrophobic resins, or if that could be modified.

*I say UV. 405nm, which is like diet UV.I mean, you can see it quite easily, so it isn't UV is it? No, we have a word for that. It's V. Ultimately, 405nm LEDs are cheap as chips and do the job just fine, so who cares.

**platform implies support, but with a feeling of "from below". This platform is at the top, the English language doesn't really have a word for something you build upon from below, and extend downward. Maybe it's just silly human bias, should we build houses from the roof down? It makes a lot of sense, it would keep the builders dry and you could crack on with the electrics practically from the start.