Hairy Plotter: Christmas tree machines

This is a story about how inventing something in one area leads to completely new inventions in places you weren't thinking about. Like when dot matrix printing technology was getting old, people started looking to bubble-jet printers as the next best thing. Where dot-matrix printers were based on impact, bubble-jet printers work by having the print head move back and forth over the paper, depositing tiny droplets of different kinds of ink at precise locations. What a beautiful technology it is! Now you can push a button on your computer and seconds later out pops a nice color picture.
As competition heated up in this sector, the size of the bubbles got smaller and the precision of the print head got finer. Soon pictures from these devices were rivaling traditionally developed photographs.
Then somebody had an idea. It was a really simple idea, like most profound ones are: what if, instead of paper and ink, we use this technology to construct things? Picture a 3-Dimensional box. The print "head" moves all across one layer of the box, depositing various chemicals. Then the next layer is done, and the next. Fairly soon your box is filled with an accurate 3-dimensional object created by your printer. Does anybody remember the "replicator" on Star Trek? Push a button and it makes anything? This would be like the "Model-T" version of that.
For the last several years, these devices have been used in industrial prototyping situations. Designers of new cars, for instance, can create an accurate model of the car in a few hours. Change the design, push a button, and you can build another one. This is much easier and cheaper than molding models by hand.
But now, more and more research is being done into these devices. Can they be used to create replacement organs, for instance? If so, you could foresee a future where the doctor "prints out" whatever part you may need. Can one of these machines make another one? If so, that opens the door to "Von Neumann probes", something the science fiction community has talked about for years.
The technology has a long way to go, sure. But the purpose of this article wasn't to provide more hype than hope. I think this technology will blossom -- and what a cool day it's going to be when that happens.