Neat x-axis printer hack from Ted Kinsman. See more here.
An x-y axis printer is made by controlling a solenoid liquid valve. Slow and small resolution, but very inexpensive to print with. Here it is printing with blue water color ink, but it mostly prints with coffee. The drip size, and the nozzle distance, and the paper can all be changed. This machine prints with and on anything.
Make a robot friend with Adafruit’s CRICKIT – A Creative Robotics & Interactive Construction Kit. It’s an add-on to our popular Circuit Playground Express, FEATHER and other platforms to make and program robots with CircuitPython, MakeCode, and Arduino. Start controlling motors, servos, solenoids. You also get signal pins, capacitive touch sensors, a NeoPixel driver and amplified speaker output. It complements & extends your boards so you can still use all the goodies on the microcontroller, now you have a robotics playground as well.