The age of smart, self-optimizing materials has begun. A programmable metamaterial has been developed that shatters the limits of old material science.
US researchers at the University of Connecticut have developed a reconfigurable acoustic metamaterial capable of controlling sound waves by bending, dampening, or focusing them.
Its applications are wide-ranging, extending from medical imaging to soundproofing.
Moreover, this material enables real-time tuning with an almost “infinite” number of possible shapes, overcoming the traditional limitation of fixed metamaterials.
“This is a big deal for our field, because usually you can have a handful of stable states that you can tune your material to, but this one here gives us more configurations than the number of atoms in the universe,” said Osama R. Bilal, assistant professor at the Wave Engineering for eXtreme and Intelligent maTErials (We-Xite) lab, in the press release on November 25.
Metamaterials, which are defined as artificial substances engineered to achieve extraordinary properties, are not a new invention. However, the past ones were mostly rigid.
Once manufactured, the material‘s function is fixed, limiting it to a specific frequency or task. If damaged, the whole material could fail.
The research team aimed to develop a material that not only controls sound waves but is also adjustable in both frequency and function.
The newly designed metamaterial is structured as an 11×11 grid of asymmetrical pillars, each with one or more concave faces resembling an apple core.
These pillars aren’t fixed, but are individually controlled by motors. This design enables minute adjustments in one-degree rotation increments.
By reorienting the pillars, engineers can tune the material’s function in real time, making it instantly adaptable.
Sound waves traveling through the grid bounce off the concave faces of the pillars. Since each pillar’s angle dictates the path, the material can be programmed to perform different functions.
Use in medicine
One of the most compelling applications lies in medicine. The metamaterial can be used to focus sound waves with extreme precision, intensifying their effect at a single point.
Bilal paints a picture of its therapeutic potential.
“Imagine something like a brain tumor – something you want to destroy, but at the same time, you can’t go in there with a scalpel. You can’t even go in there with very high-intensity sound, at the beginning,” he explained.
“So you need to have very low-amplitude waves that will focus only on a single point, and after that will disperse.”
This technique could non-invasively weaken a tumor, attack a kidney stone, or manipulate small particles inside the human body — tasks currently difficult or impossible with conventional methods.
Altogether, the technology promises to enhance medical imaging techniques, such as ultrasound and acoustic tweezers.
Experts are also applying these metamaterials to reduce drag forces on moving objects, aiming to save energy and fuel.
The AI navigator
The sheer scale of design possibilities presents its own challenge.
With literally infinite configurations, manually calculating how each one affects sound is impossible.
To navigate this cosmic design space, the team is now turning to AI algorithms and heuristics. These tools provide insight into the material’s sound propagation behavior under different configurations.
“The end goal will be a fully autonomous material that has both the ability and intelligence to optimize its performance through machine learning,” said Billal.
It will be interesting to see how this new metamaterial advances future technology.
The study was published in the journal Proceedings of the National Academy of Sciences (PNAS).