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'We're storing how this material should behave': Boffins' 3cm 'm-bit' cubes demonstrate programmable wunderstuff

Raising possibility of buildings that flex in earthquakes, and much more

Engineers working in Switzerland say they have developed a method of writing data directly into materials, a process that changes the material's physical properties at the same time.

The study, published in Nature this week, could lead to the development of materials that possess programmable properties, which have engineering applications from athletic footwear to earthquake-resistant buildings.

A team including Mark Pauly, Pedro M Reis and Tian Chen of Swiss university École Polytechnique Fédérale de Lausanne developed the metamaterial that can store data.

Metamaterials are engineered and do not exist in nature. They often have properties "designed-in" and are built up from subcomponents. The problem is that after they are made, metamaterials have fixed properties.

Chen and colleagues' idea was to make a metamaterial that could store data and be programmed to exhibit particular properties. Data could also be read from the material to understand its properties.

They have built a proof of concept consisting of cubic cells, 3cm across. Each cell includes flexible pre-bent beams, a magnetic cap, and a stopper. Stimulated by a magnetic field, the cap can move up or down, preventing the beams from moving further, or allowing them to be more flexible (see diagram). The cells are dubbed mechanical bits, or m-bits, by the researchers, who positioned them in a 6x6 arrangement that could store 36 bits of data in a process analogous to writing data onto a computer hard drive.


The diagram above shows more detail of the concept (click to enlarge)

But the data was not stored to be retrieved by a program. It actually changes the physical properties of the material. A cell in its uncompressed state is stiffer than one that is compressed. The researchers also demonstrated that the state of the material could be read using an electromagnet. They wrote stripes, checks, and – because they are engineers – a smiley face onto the array and showed that the patterns could be read remotely.

Chen told The Register: "Our intention was not to store data for the sake of storing data – we already have data storage devices. We wanted to store behaviour as data. We're storing how this material should behave. We're not storing a binary string of zeros and ones; we're storing Young's modulus (elasticity), stiffness, strength, and the energy absorption characteristics."

Metamaterials are already used in Nike running shoes [PDF] to help absorb the energy of each foot strike on the ground. Chen said such materials had the potential to be programmed to adapt to the running terrain.

Other applications might include making buildings more resistant to earthquakes by being able to alter their flexibility and energy absorption on the fly according to the properties of the tremors.

"I think it will be useful to tune this material in real time to target a specific scenario," Chen said.

But researchers working in the field need to overcome some limitations. The first is scaling down. Here, developments in 3D printing of silicone should help, Chen said.

"As long as we don't go into the quantum scale. It can be scaled down without changing really anything. It's so the limitation, from our perspective, is the fabrication."

The other problem is developing a material that can be written to and read in three dimensions, rather than the current planar formation.

"That's something that digital storage devices aren't able to do either," Chen said. "We're trying to figure out, theoretically, if it's feasible to program one unit within a 3D grid, without affecting a neighbouring unit."

Nonetheless, merely demonstrating that ability to make a material store data that affects its properties is an exciting development, according to Corentin Coulais, assistant professor in soft matter physics at the University of Amsterdam.

"Just as hard drives revolutionised computer systems, devices such as this could open the door to the next generation of soft robots and engineering materials, or to any application in which it would be useful to program the mechanical properties of a device remotely," he said in an accompanying commentary piece.

"This early example of remotely programmable matter opens the way for materials to process data, compute and learn." ®

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