Sample metamaterial manufactured by 3dprinting

Traditional materials research focuses on creating new materials by adjusting their chemical properties. The metamaterials research explores ways to precisely tune the structure using techniques like 3D printing to achieve the same results. Most of this research has focused on relatively small things at the micro or nano scale.

Now researchers at Technology Innovation Institute’s [TII] Advanced Material Research Centre (AMRC) are exploring how metamaterials could scale to larger structures like buildings. This research could lead to safer buildings that are more resilient to vibration or earthquakes.

“There is a lot of research on metamaterials, but not so much on big structures like buildings,” explained, Vincenzo Giannini, Director – Smart and Metamaterials at AMRC. “Our idea was to target civil engineering structures such as buildings.”

3D illustration, abstract background in the form of cubes and linear structures.

Starting small to go big

Metamaterials allow designers to imbue properties from the structure of the materials rather than the material itself. “This helps you to design a structure so the final material has properties you like but could not find in nature,” Giannini said.

Researchers are in the initial stages of figuring out how to scale metamaterial techniques to larger things. The TII researchers have started by identifying some patterns that show the most promise from a theoretical standpoint. Further research will be required to actually build them.

The main innovation was to find ways to dampen the movement of vibrational waves, called phonons, in buildings. The research found ways of adding particular patterns to create a bandgap that blocks phonons of a specific frequency. This could be helpful when designing buildings that are less responsive to known vibrations, like the expected effects of cars on a bridge.

Laying the groundwork

This early research focuses on laying the groundwork for more specific applications down the road. “We wanted to give a more general approach for creating a system that could adapt to what designers need for specific situations in the future,” Giannini said.

One possibility might be to design special coatings, sheets, or liners that could help isolate sound and vibrations. Giannini said, “Now we are going in the direction of making it thinner, smaller, and lighter. Instead of working on the building, you could put this liner on top of other structures.”

If things go well, this could lead to some of the first noise and vibration-dampening liners within a couple of years. In the meantime, more research will be required to put these new metamaterials into practice. “We are hoping to work with other researchers to accelerate research and development of metamaterials for larger structures,” Giannini said.

This picture shows how the structure of metamaterials can reduce sound vibrations.

: The artwork “Órgano” by sculptor Eusebio Sempere is a large-scale example of a phononic crystal: it consists of a periodic array of cylinders in the air (the ‘metamaterial’ or ‘crystal structure’) and its dimensions and pattern is designed such that sound waves of specific frequencies are strongly attenuated. It became the first evidence for the existence of phononic band gaps in periodic structures

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