A Computer that operates on water droplets developed by Stanford engineers
Researchers have gone back to natural resources, most of them are using cheap renewable sources like water and trees to develop scientific innovations. Recently researchers from Sweden and the US developed high capacities 3D soft batteries from trees. Currently engineers from Stanford have developed a computer that operates on water droplets.
Manu Prakash, an assistant professor of bioengineering at Stanford and his students have developed a synchronous computer that operates using the unique physics of moving water droplets. Their goal is to design a new class of computers that can precisely control and manipulate physical matter. It has taken the team a number of years to finally come up with the computer since water and computers don’t mix. Prakash got the idea of developing that computer when he was still a graduate student. The work combines his expertise in manipulating droplet fluid dynamics with a fundamental element of computer science. In this work, we finally demonstrate a synchronous, universal droplet logic and control,” Prakash said.
Because of its universal nature, the droplet computer can theoretically perform any operation that a conventional electronic computer can do, although at significantly slower rates. Prakash and his colleagues, however, have 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,” Prakash said. “Our goal is to build a completely new class of computers that can precisely control and manipulate physical matter. Imagine if when you run a set of computations that not only information is processed but physical matter is algorithmically manipulated as well. We have just made this possible at the mesoscale.”
Prakash when he was still in school the idea grew in his head until the day he decided to create a rotating magnetic field that could act as clock to synchronize all the droplets. The idea showed promise, and in the early stages of the project, Prakash recruited a graduate student, Georgios “Yorgos” Katsikis, who is the first author on the paper. Computer clocks are responsible for nearly every modern convenience. Smartphones, DVRs, airplanes, the Internet – without a clock, none of these could operate without frequent and serious complications. Nearly every computer program requires several simultaneous operations, each conducted in a perfect step-by-step manner. A clock makes sure that these operations start and stop at the same times, thus ensuring that the information synchronizes.
“The reason computers work so precisely is that every operation happens synchronously; it’s what made digital logic so powerful in the first place,” Prakash said.
Developing a clock for a fluid-based computer required some creative thinking. It needed to be easy to manipulate, and also able to influence multiple droplets at a time. The system needed to be scalable so that in the future, a large number of droplets could communicate amongst each other without skipping a beat. Prakash realized that a rotating magnetic field might do the trick. Katsikis and Prakash built arrays of tiny iron bars on glass slides that look something like a Pac-Man maze. They laid a blank glass slide on top and sandwiched a layer of oil in between. Then they carefully injected into the mix individual water droplets that had been infused with tiny magnetic nanoparticles.
Next, they turned on the magnetic field. Every time the field flips, the polarity of the bars reverses, drawing the magnetized droplets in a new, predetermined direction, like slot cars on a track. Every rotation of the field counts as one clock cycle, like a second hand making a full circle on a clock face, and every drop marches exactly one step forward with each cycle. A camera records the interactions between individual droplets, allowing observation of computation as it occurs in real time. The presence or absence of a droplet represents the 1s and 0s of binary code, and the clock ensures that all the droplets move in perfect synchrony, and thus the system can run virtually forever without any errors.
The current chips are about half the size of a postage stamp, and the droplets are smaller than poppy seeds, but Katsikis said that the physics of the system suggests it can be made even smaller. Combined with the fact that the magnetic field can control millions of droplets simultaneously, this makes the system exceptionally scalable.
“We can keep making it smaller and smaller so that it can do more operations per time, so that it can work with smaller droplet sizes and do more number of operations on a chip,” said graduate student and co-author Jim Cybulski. “That lends itself very well to a variety of applications.”
Prakash said 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.
The team intends to make the droplet circuits available to the public. “We’re very interested in engaging anybody and everybody who wants to play, to enable everyone to design new circuits based on building blocks we describe in this paper or discover new blocks. Right now, anyone can put these circuits together to form a complex droplet processor with no external control – something that was a very difficult challenge previously and now people will be able to see the computer that operates on water droplets.,” Prakash said.
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