I stumbled upon a handheld inkjet printer and bought it for about 150 € (including shipping/taxes) fascinated by all the possible projects. It has a rotary encoder on the side, so theoretically it can detect the speed of you moving your hand and prints accordingly.
It uses HP 45 inkjet cartridges that can be bought on eBay for about 10 €. HP45 cartridges are all black as for what I've seen. HP44 looks similar from a form factor but won't work since the pins are different (see picture below). Besides that, the cartridge that came with the printer has a different ink. It dries faster and seems to stick better to metal and other smooth surfaces. Since I intend to print on paper and textiles, for now, I use the standard HP45 cartridge. I guess you could easily refill with any color as soon as one has an empty one… more on that later.
First test prints
Printing on cotton
The real advantage of this handheld device is played out on uneven and otherwise hard to print surfaces like cloth/textiles. There is a celebration coming and I took the opportunity to produce unique invitations.
I designed the invitations in Inkscape since I know the program fairly well and I prefer to handle vectorized data. The size limitation of the handheld printer is somewhere around 8000 pixels horizontally and 150 pixels vertically. Therefore I split the invitation of about 1m in half, i.e. in two files printed consecutively. Before the printer can process the file it has to be the right format, which is monochrome .bmp. I used GIMP to import the png from Inkscape and converted it by Image-> Mode -> indexed.
The address on the envelope could also be printed. A lot of good advice and help came from the other people involved and without whom I couldn't have done this. For example, I didn't have the patience to cut out even one strip straight… Regarding the rotary encoder: The precision is not that good but acceptable I guess. I ended up trying to print at an even pace. Accelerating the speed (or moving the rubber band of the encoder) resulted in invitations of different lengths with a slightly stretched font.
There will be more projects with this fun tool. More on this later…