[gaze]

It's the nozzle. Let's suppose you really wanted to design your own nozzle... you could use something like MUMPS, which is $5,800 for 15 dice, plus 100 for each additional. You have to wrestle together 15 people to pay 400 bucks (or 20 to pay 300, and so forth) for a printhead that probably won't work. Figure it'll take several iterations and everyone needs to be in for thousands and thousands of dollars.

It's doable but only among a group of very wealthy hobbyists.

People with this kinda money typically gravitate towards high vacuum projects and microwave electronics

[gaze]

This is ignoring all the high-speed cameras and lab equipment for characterizing the electrical and rheological properties of the ink you shoot through it...