How engineers built the world's first water computer

Stanford's Manu Prakash created a computer clock made of water droplets trapped in a magnetic field that could have biological and chemical applications, as well as change the way scientists think about computation.

When Manu Prakash was a graduate student at the Massachusetts Institute of Technology, he envisioned a computer operated by droplets of water. Almost 10 years later, Dr. Prakash, now an assistant professor of bioengineering at Stanford University, has brought his idea to fruition.

Flanked by graduate student assistants Jim Cybulski and Georgios Katsikis, Prakash built a computer clock – the system at the heart of every computer that keeps operations moving in sync – using tiny water droplets that could be moved and manipulated while trapped in a magnetic field.

"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 in a Stanford News report.

As the report explains, the clock is essentially a tiny maze of iron bars held in oil between two glass slides. The research team injected water droplets infused with magnetic nanoparticles into the system and turned on the magnetic field, setting the clock into a series of rotating or flipping motions that, because it all works in synchrony, could run forever. Each time the magnetic field flips, the polarity of the bars changes and each droplet moves through the maze one spot at a time, with binary 1s and 0s indicating either the presence or absence of a drop in each spot with every flip.

"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," Katsikis said in the report. "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."

Nature Physics published the results of their work on Monday.

While Prakash explained the significance of the work as a breakthrough in thought regarding computation and the manipulation of matter, he said not to expect water-based computers to replace the digital ones we now use for everyday purposes.

"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 in the Stanford report. "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."

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