Engineers build first water-based computer

Engineers with Stanford University on the U.S. west coast have designed a computer that runs entirely on water droplets and can perform like regular computer, only at a much slower pace.

Professor Manu Prakash, at the university's Bioengineering Department, and his team have been working on the idea for almost a decade. The computer resembles a microchip, the size of a postage stamp, but researchers claim that it is enough to prove their idea. Prakash surprised the world last year when he created a paper microscope that folds like Origami, known as the Foldscope.

In the microchip, with circuitry pattern similar to a Pac-Man maze, the researchers trapped tiny water drops infused with magnetic nanoparticles. When they placed rotating magnets underneath the circuit, the droplets moved in a synchronized way, resembling binary code, the language used in computing.

The core of the feat was not so much having built the first computer that runs on water, but rather the fact that the droplets can carry chemical or biological materials, turning the device into a potential high-speed laboratory. It can hold millions of such droplets, said Prakash, in even more reduced devices.

The study describing the water computer has been published this week in Nature Physics, with all technical details of how the device works.

"We can keep making it smaller and smaller so that it can do more operations per time," said graduate student and co-author Jim Cybulski. "So that it can work with smaller droplet sizes and do more number of operations on a chip."

Crucial to the device, as with any computer, is the clock, Prakash said. Without it, the droplets would march like soldiers without a band; one of them would fall out of pace and eventually, the whole group. "The reason computers work so precisely is that every operation happens synchronously; it's what made digital logic so powerful in the first place."

One of the many applications for the water-based device is it can be turned into a high-throughput chemistry and biology laboratory. Instead of running reactions in bulk test tubes, each droplet can carry some chemicals and become its own test tube, and the droplet computer offers unprecedented control over these interactions.

Prakash said he plans to make a design tool for these droplet circuits available to the public, so that people can assemble the basic logic blocks and make any complex droplet circuit they desire. Endite