A metamaterial that is capable of counting to ten

July 3 () –

Physicists from the Netherlands have presented in the journal Physical Review Letters and rubber-based metamaterial that can count to ten and even remember the order in which it is pressed.

“I like to find complexity in simple things,” explains AMOLF Amsterdam PhD candidate Lennard Kwakernaak, presenting a piece of soft rubber with 22 paired beams. “This is our lightning counter. Push it,” he says. it’s a statement.

The result is unexpected. All bars bend to the left except the first, which bends to the right. “That first bar then pushes the next pair to the right and moves through one position each time you push the material. That’s how the material counts to ten.”

The rubber block is an example of a mechanical metamaterial: a material whose properties are determined not only by its composition but also by its structure. Professor Martin van Hecke’s group at Leiden University investigates how simple materials can be used to process information, a bit like a computer.

A bar that adjusts from left to right can be compared to a computer bit that is zero or one. “It’s not easy to design the structure to respond the way we want it to,” explains Kwakernaak. “Counting is the simplest calculation we could come up with, so that was a logical starting point.”

“In developing such a material, one tries to discover the rules of the game,” explains the PhD candidate. “What is it allowed to do? The rule in this case is about a bar’s contact with its direct neighbors.”

The researchers also went a step further than counting, he explains. Along the way, I discovered that you can cause different reactions in the rubber by pushing with different levels of force. By experimenting with this, I was able to make a metamaterial that only counts to the end if you push it in the right order, with the right amount of force. force. A kind of padlock, in other words.

One possible use is to count cars of different weight classes going over a bridge. Or a pedometer, for example, because you can make the metamaterial as big or small as you want. “The big advantage is that such mechanical metamaterials are cheap, robust, and low-maintenance,” says Kwakernaak.

“That makes them interesting for all kinds of applications. It’s hard to say exactly what they will be, but we always find a purpose for new materials like this. For example, previous research on a material that folds like origami inspired the folding of solar panels on a satellite“.

Kwakernaak himself especially enjoys seeing how seemingly simple things can be very complex. “How exactly such a thin beam is bent is much more complicated than you think. A computer can barely simulate it.” He laughs, “Sometimes it almost feels like he’s a professional amateur.”

Kwakernaak’s next step is to devise an even more complicated structure, where there is interaction between neighbors not just in one direction, but in one plane. “That would actually be a simple computer,” says.