We just got a huge step closer. It's called CLIP (Continuous Liquid Interface Production), and it doesn't work like any other 3D printer created so far.
You use a liquid resin and an oxygen-permeable window. And then you fire light through the window to solidify the resin in only the places you want - and drain the rest. It's called tunable
This has three key advantages:
1. It's much faster than traditional 3D printing (Did I ever think I'd use that phrase?). Objects that would take hours or even days to create using normal additive printing can be done in minutes. This is particularly useful for medical applications such as dental implants or prosthetics - the object can actually be made while the patient is in the office, saving everyone time and money.
2. It's much finer than traditional methods. They've created objects with "feature sizes" below 20 microns. That's less than a quarter of the width of paper, people. This is not quite in the true nanotech realm, but it's close, close, close. They can, thus, make objects that couldn't be made using additive methods. It eliminates the limitation of not being able to have a higher part of the object more than X larger than the base.
3. It may, and I stress may, allow new materials to be used that haven't been printed with before, including nylon and ceramics.
No word on how much these 3D printers will cost - they will probably not be something you can have in your home any time soon. But...well...