Coder Matt Bell is continuing to improve his exceedingly clever water-based display screen. Inspired by a Jeep display that spelled out words with falling water, Bell's design consists of a water tank connected to a grid of clear plastic tubes and an Arduino. Individual solenoid valves at the bottom of each tube can let in air, creating the effect of individual white pixels on a black screen, and preprogrammed sequences can spell out letters or numbers. His newest version adds an air reservoir to control the size of the bubbles, as well as completely separate vinyl tubes rather than one large tank with dividers. You can see the display below or read about the process of creating it here and here.