Researchers Minsoung Rhee and Mark Burns at the University of Michigan have created an 8 bit processor using logic gates made of pneumatic valves. Besides just being awesome, the processor does have a practical use- it is designed to control a microfluidic medical device. By powering both the processor and the chemical reactors using air, the group hopes to create medical devices that don’t rely on electricity to run.
The main article is behind a paywall, however the supplemental article describing the logic gates is available for free, as well as some neat videos of the logic gates in action.
So, someone want to make a steam-powered version?