Inspired by persistence of vision (POV) projects, Sagarrabanana built a system that incrementally dispenses water as pixels on a flat surface, creating ephemeral dot matrix text/images. This so-called “Bikelangelo” device is towed by a bicycle for ultra-mobile marking, and uses a pressurized tank for fluid storage.
As he pedals, a series of seven valve open and close under Arduino Nano control. A Hall-effect sensor allows it to dispense accurately based on the bike’s speed, and a Bluetooth phone connection via an HC-05 module is implemented for text input on-the-go.
You can see Bikelangelo in action in the quick clip below, and more information about the project – including two longer videos in Spanish – is available in Sagarrabanana’s write-up.