This is a peristaltic pump used in medical machinery. It can be used when it is necessary to supply small and precise quantities of liquids. To make it work you need 3 ball bearings (skateboard / rollerblade), a stepper motor (nema17 or 23 - arduino controlled) and a silicone rubber tube with a diameter of 10mm.

Sorce code for Arduino: https://github.com/zmaker/arduino_cookbook/tree/master/332-peristaltica