Thanks everyone for the pointers. @soysauce, I'd probably be fine with anything over 100dpi. Any pointers to industrial heads or ballpark guesses on price?
I'm interested in experimenting with inkjet print heads: mounting them on a CNC machine to make a flatbed printer, alternative inks (eg., bioprinting or UV-curing inks), building my own electronics to control the print head, that sort of thing. Could you help me choose a good place to start...