Interesting comment from last time this was posted https://news.ycombinator.com/item?id=48093670 Inkjet printing requires orders of magnitude more engineering expertise, materials science, industry experience and financial resources than most people imagine. That is the reason, open inkjet printers don't exist despite having been consumer products with the same drawbacks for more than forty years. That is why this is…
On the technology side, I'm somewhat hopeful because it looks like they're using off-the-shelf HP ink cartridges for this. HP cartridges embed the printhead into the cartridge itself, and that printhead is arguably the most complicated part of the entire device. Outsource the printhead, and you're just designing a plotter with a PCL interface. I agree that the bigger challenge is going to be patents. It also wouldn't…
Instead they use the fact mosfet gates have capacitance, and can therefore store 1 'bit' of information. Through a network of hundreds of MOSFETs, the right bits can be put on all the nozzle gates as needed, and then a 'fire' pulse is sent which for around a microsecond turns on a tiny heater (or not, depending on mosfet gate state). The heater boils some ink, making a pressure wave which travels down a pipe and makes a drop of ink fly out towards the paper. That heating and cooling again can happen around 10,000 times per second per nozzle (and there are ~300 nozzles).
I suspect this decision is because the custom silicon process needed to manufacture these nozzles is cheaper if they only have n type MOSFETs - and without p type MOSFETs you can't make a typical push pull logic gate.
The nozzles themselves are quite a lot of silicon - perhaps 100mm^2, with deep etched holes, and are effectively disposable, so I assume huge efforts have been taken to reduce costs - including this curious electrical design.
The protocol also is hugely irregular, which I suspect might be to avoid any wires on the chip needing to cross eachother.