Add printing capability to any microcontroller project with just the innards of a thermal printer. Thermal printers are also known as receipt printers, they're what you get when you go to the ATM or grocery store. Now you can embed a little printer of your own into a custom enclosure of your choosing. This printer is ideal for interfacing with a microcontroller, you simply need a 3.3V-5V TTL serial output from your microcontroller to print text, barcodes, bitmap graphics, even a QR code!
This is the super hackable version! All that's included is the guts of a thermal printer: the motor/heater with a flex cable and a control board with a chip that will take your serial commands and use them to drive the motor & heater. You also get a TTL cable and a 33' roll of thermal paper. You'll likely want to design some sort of enclosure for it, especially since its a little challenging to line up the paper so it feeds through straight. That said, because there's no paper bay you can use as little or as much paper as you like, heck you can even feed in a mobius strip!
To power it, supply the VH pin with 5-9VDC. 5V can be a little dim, 7.5V-9VDC will give you nice dark printing.