Stanford Engineers 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.
“In this work, we finally demonstrate a synchronous, universal droplet logic and control,” Prakash, an assistant professor of bioengineering at Stanford said.
Because of its universal nature, the droplet computer can theoretically perform any operation that a conventional electronic computer can crunch, although at significantly slower rates.
The results are published in the current edition of Nature Physics.
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. A rotating magnetic field might do the trick.
They 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.
“Following these rules, we’ve demonstrated that we can make all the universal logic gates used in electronics, simply by changing the layout of the bars on the chip,” said Katsikis. “The actual design space in our platform is incredibly rich. Give us any Boolean logic circuit in the world, and we can build it with these little magnetic droplets moving around.”
A simple-state machine including 1-bit memory storage (known as “flip-flop”) is also demonstrated using the above basic building blocks.
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.
“If you look back at big advances in society, computation takes a special place. We are trying to bring the same kind of exponential scale up because of computation we saw in the digital world into the physical world.”
