Weighing in at 11 ounces, the Mini Mobile Printer from ZUtA Labs packs a couple motors, a circuit board, an ink cartridge, and an inkjet into a cylinder about 4 inches tall and 5 inches in diameter.
The printer works by driving itself across a sheet of paper and depositing ink as it goes. It rides on 4 omni-wheels, and thanks to the unique properties of those wheels this little robot can move in any direction while depositing ink.
It's by no means the highest resolution printer (the prototype has a resolution of 192dpi x 96dpi, far short of the 1200dpi available in most full sized printers), and due to the size limitations of the shell it is limited to grayscale. But this printer is good enough to print an A4-sized sheet in about a minute. The battery is good for up to an hour, and the cartridge is reportedly good for around a thousand pages before it needs to be replaced.
And all for the low, low price of$180 (the white model costs $200). That is pretty expensive, and not just because the resolution is low and the battery is limited.
I went looking for comparable mobile printers, and the one I like most is the HP OfficeJet 100, which offers 5 colors, high resolution, and can print several pages per minute, all for $120 (refurb) or $199 (new).
True, the HP printer isn't as cool as the robot shown above but if I were going to buy a mobile printer I would pick one based on how much it would help me get work done. The robot printer shown above is a great conversation starter but as a functional tool it leaves a lot to be desired.