and why the hell do they not mind that their picture is being shown all over the internet?

It’s a great idea, actually. Most people don’t know how the printers work. HP cartridges are the only ones this will work with (most others have a separate print head, which means more cost if you damage something). Now, the link to parallax posted farther up I’ve known about. I like this one better due to the more general purpose response and the SIGNIFICANTLY LARGER TANK! The parallax one uses one of the tiny cartridges. Also, since this one is the larger, single color tanks, it’s easier to make a full color print.

Now, printers these days are dirt cheap, I know. I’m also not a fan of HP, but I do know of one real use for this. There’s a lot of people who make their own CNC routers these days. Replacing the router head with a single cartridge or a “color box” would give you large scale printing capability, say, if you wanted to make your own plotter. It would also let you print on things that you normally couldn’t shove through a plotter.

I do see another option for the handheld unit beyond what’s suggested by the writer: add a wheel encoder, so the microcontroller can time its printing and you get something more consistently legible!

I wonder if there’s a pressure hole like on Epson cartridges, so you could put a little pressure (only a PSI or two probably) that could help keep the flow going.