someone who can count to ten

“One, two, three… fourteen” spoken from the mouth of an inanimate piece of cement is closer than ever.

In the long, fast-paced, and often fascinating race to develop new materials, a team of physicists in the Netherlands has just achieved something astonishing: a metamaterial that can count to ten. And even remember the order in which you press it. Those responsible have recorded a video demonstrating the amazing properties of their creation, as if it were some kind of sleight of hand. All you need is a small block.

Now they are thinking about possible applications.

A metamaterial that can count? True, it sounds crazy, but that’s what Leiden University in the Netherlands claims. Professor Martin van Hecke and PhD student Lennard Kwakernaak, the authors of a paper published in Physical Review Letters, explain how they created a rubber block with amazing properties. The flexible sheet part is an example of a mechanical metamaterial that can count and remember the order in which pressure is applied to it.

What exactly? “Irreversible metamaterials that count cycles of mechanical conduction and store the results in easily interpretable internal states.” That’s how they present it in their paper. The explanation may be a bit dry, but it’s much better understood by watching a demonstration video that Lennard Kwakernaak himself recorded using a small rubber block made of 22 flexible beams grouped in pairs.

When the block is pressed, all the rods bend to the left. All except the first one, which turns to the right. If you repeat the process, something similar happens, although the number of sheets oriented to the right increases. Each block turned in this way has a mark that helps you determine how many times the block has been pressed. “This first rod pushes the next pair to the right and moves one position each time the material is pushed. That’s how it counts to ten,” explains the Leiden researcher.

What is a metamaterial? The concept is not new. Metamaterial refers to artificially structured materials with unusual properties that are not easily found in nature. Research into them has been particularly fruitful over the last two decades, and at Hatake we have already told you about some that can act as “acoustic lenses,” absorb vibrations without losing rigidity, or even move without the slightest contact, using only their response to sound waves.

More precisely, the rubber block is a mechanical metamaterial, a label given to those materials whose properties depend on both their composition and structure. One of its big advantages, says Kwakernaak, is that creations like the one he proposes are relatively inexpensive, robust, and low-maintenance. “That makes them interesting for all sorts of applications.”

And what applications will it have? “It’s hard to say what they will be, but we always find applications for these new materials. Previous research on a material that folds like origami inspired the folding of solar panels on a satellite,” says Kwakernaak. At Leiden University, they finally remember that a strip that can be adjusted from left to right can be compared to a computer bit, and show possible future applications, for example, for counting vehicles of different classes or in pedometers.

The metamaterial’s capabilities go beyond its ability to detect pressure. The researcher says that it can, in a certain way, differentiate between them. “I found that you can elicit different reactions in the rubber by pushing it with different forces,” he adds. “By experimenting with this, I was able to create a metamaterial that only counts to the end if you push it in the right order. In other words, with the right amount of force.

So what now? The researcher wants to go further and design an even more complex structure, in which the interactions of the rods are not in one direction, but in a plane. “It would be a simple computer, really,” notes Kwakernaak. It won’t be easy. “How exactly to bend such a thin beam is much more complicated than it looks. A computer can barely simulate it,” he says.

“Our metamaterials are robust, scalable and extensible, enabling better understanding of temporal memories of complex environments and opening up new possibilities for intelligent sensing, soft robotics and mechanical information processing,” the newly published study emphasizes.

Images | Leiden University

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*The previous version of this article was published in July 2023.