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Published in Nature Communications, researchers from St. Olaf College and Syracuse University built a computer made entirely of mechanical components that can perform simple computations without  electricity or batteries. 

“We typically think of memory as something in a computer hard drive, or within our brains,” said St. Olaf College Associate Professor of Physics Joey Paulsen. “However, many everyday materials retain some kind of memory of their past—for example, rubber can ‘remember’ how far it has been squeezed or stretched in the past. The research team wanted to understand if we could use everyday materials to not only remember movement but also process information––or compute.”

Led by Paulsen, the research team used common materials, such as steel springs and bars, to create three mechanical computers. The first could count how many times it was pulled back and forth. A second distinguishes whether it has been pushed an odd or even number of times. The third can remember if a medium or large amount of force was applied. 

“We now have a rational way of building these machines that can perform simple computations without a computer chip or a power source,” Paulsen said.

Key findings from the research include:

• Mechanical computers can perform simple computations without a computer chip or  power source. 
• Mechanical computers are able to harvest their power from physical force, rather than electricity. 
• Proof of design that mechanical computers could be a viable alternative to conventional computers in harsh settings—such as extreme temperatures or exposure to corrosive chemicals—when only simple computations are needed. 

“Our results are one step towards designing materials that can sense their environment, make a decision, and then respond,” said Paulsen. “Frequently called smart materials, what we learned could help improve people’s lives by having more responsive artificial limbs or tactile rooms.”

Paulsen recommends that future research on mechanical computers focus on understanding their limitations and scalability. Under his leadership, St. Olaf students are currently testing how the state of one rotor affects its interaction with a second rotor –– and potentially a third. This research will continue in the coming months, with opportunities for students to participate through the college’s Collaborative Undergraduate Research and Inquiry (CURI) program. 

This research was funded by the Aspen Center for Physics, Syracuse University, and St. Olaf College. This work was supported by the National Science Foundation (grant number PHY-2210452) through the Aspen Center for Physics.