According to LiveScience, the trick involves using a superhydrophobic surface that tilts every time a drop of water hits it. Scientists have calibrated the rig so that they can guide the drops to a specific destination on the board which will then register its position.
Using the tracks, the researchers demonstrated that water droplets could be turned into technology, "superhydrophobic droplet logic." For example, a memory device was built where water droplets act as bits of digital information. Furthermore, devices for elementary Boolean logic operations were demonstrated. These simple devices are building blocks for computing.
Adding intrigue to the endeavour is that those water droplets could hypothetically carry a chemical compound which could potentially react with the surface (currently comprised of copper coated in silver and a fluorinated compound), which could have interesting applications for building micro chemical reactors. But for now, let's just enjoy the fact that we could have water-powered computers, yeah? [LiveScience]