In the absence of electronic computational tasks, our daily lives would be drastically different. Everyday devices like elevators, vending machines, turnstiles, washing machines, and traffic lights rely on simple electronic computing to switch states. But what if these devices could operate without a power supply? A research team led by Martin van Hecke from Leiden University and AMOLF has demonstrated how smart rubber structures can carry out these computational tasks. “We now know how to design simple materials so they can process information,” van Hecke stated.

Their study, published on May 20 in the Proceedings of the National Academy of Sciences, showcases a groundbreaking approach to computation using mechanical systems. Traditionally, electronic devices perform calculations with digital bits and complex circuits. However, the researchers have found an innovative way to compute using slender rubber elements as mechanical bits, assembling them into a “metamaterial.” The key to making these materials function as machines lies in controlling the interactions between the individual bits.

A Binary Counter

As an initial demonstration, the research team developed a rubber computer capable of acting as a two-bit binary counter. As shown in their accompanying video, stretching the metamaterial causes it to count from “00” to “11,” and releasing it returns the count to “00.” This device utilizes pre-curved rubber beams as mechanical bits, with interactions mediated by connecting them. This configuration allows information to be stored and processed. Counting is a fundamental example of a finite state machine, and this rubber device could be used to control the motion of a simple robot’s legs.

“A significant experimental breakthrough occurred in the last month before my return to China during the pandemic,” said researcher Jingran Liu, who was a visiting Ph.D. student at Leiden University and AMOLF and is now a postdoc in Madrid. “We suddenly realized how to design a more complex three-bit system, and within a few days, we had made four working samples.”

More Powerful Metamaterials

The researchers quickly discovered that three-bit metamaterials were far more powerful than their two-bit predecessors. “Depending on how these samples are manipulated, they can perform seventeen different simple calculations,” explained AMOLF postdoc Lishuai Jin.

For instance, these metamaterials could replicate the functionality of a turnstile. “A turnstile manages entry with its rotating arms—locking and unlocking in response to the insertion of coins and the push from customers. Our metamaterials can emulate this mechanism through a specific sequence of states and driving pulses,” said Jin. Additionally, the rubber computer can be used for a combination lock, vending machine, and many other applications.

A New Era of Computing

“Our work shows that complex computations can be performed by smart metamaterials, in a manner that is completely different from traditional computing,” said Liu. “What I find very exciting is that our principles are not limited to mechanics. Moreover, complex memory effects, which are important in physics but difficult to study, can now be used for something extremely useful: efficient computing.”

This revolutionary approach to computation using smart rubber structures opens up a new world of possibilities for powering devices and carrying out tasks without relying on traditional electronic components.

By Impact Lab