A group of bioengineers led by Dr Manu Prakash of Stanford University has developed a synchronous computer that operates using the physics of moving water droplets.

Because of its universal nature, the water-droplet computer can theoretically perform any operation that a conventional electronic computer can crunch, although at significantly slower rates. Dr Prakash’s team, however, has a more ambitious application in mind.

“We already have digital computers to process information. Our goal is not to compete with electronic computers or to operate word processors on this. Our goal is to build a completely new class of computers that can precisely control and manipulate physical matter at the mesoscale (10 microns to 1 millimeter),” Dr Prakash explained.

The ability to precisely control droplets using fluidic computation could have a number of applications in high-throughput biology and chemistry, and possibly new applications in scalable digital manufacturing.

In a new paper published online in the journal Nature Physics, Dr Prakash’s team describes the fundamental operating regime of the system and demonstrates building blocks for synchronous logic gates, feedback and cascadability – hallmarks of scalable computation. A simple-state machine including 1-bit memory storage (known as ‘flip-flop’) is also demonstrated using the basic building blocks.

“Our platform uses a rotating magnetic field that enables parallel manipulation of arbitrary numbers of ferrofluid droplets on permalloy tracks.”

“Through the coupling of magnetic and hydrodynamic interaction forces between droplets, we developed AND, OR, XOR, NOT and NAND logic gates, fanouts, a full adder, a flip-flop and a finite-state machine. Our platform enables large-scale integration of droplet logic, analogous to the scaling seen in digital electronics, and opens new avenues in mesoscale material processing.”

“The current chips are about half the size of a postage stamp, and the droplets are smaller than poppy seeds, but the physics of the system suggests it can be made even smaller,” said team member Georgios Katsikis of Stanford University.

“Combined with the fact that the magnetic field can control millions of droplets simultaneously, this makes the system exceptionally scalable.”

Dr Prakash added: “the most immediate application might involve turning the computer 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.”

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Georgios Katsikis et al. Synchronous universal droplet logic and control. Nature Physics, published online June 08, 2015; doi: 10.1038/nphys3341