Smart Material Challenges Newton’s Laws of Motion

Andrew Corselli

The prototype metamaterial, pictured above and below, uses electrical signals transported by these black wires to control both the direction and intensity of energy waves passing through a solid material. (Image: Eric Stann/University of Missouri)

For more than a decade, Dr. Guoliang Huang, the Huber and Helen Croft Chair in Engineering at the University of Missouri, has been investigating the unconventional properties of “metamaterials” — artificial materials that exhibit properties not commonly found in nature, as defined by Newton’s Laws of Motion — in his pursuit of designing the ideal metamaterial.

His goal is to help control the “elastic” energy waves traveling through larger structures — e.g., an aircraft — without light and small “metastructures.”

“For many years I’ve been working on the challenge of how to use mathematical mechanics to solve engineering problems,” Huang said. “Conventional methods have many limitations, including size and weight. So, I’ve been exploring how we can find an alternative solution using a lightweight material that’s small but can still control the low-frequency vibration coming from a larger structure, like an aircraft.”

Now, Huang’s closer to his goal. In a new study published in the Proceedings of the National Academy of Sciences (PNAS), Huang and his colleagues have developed a prototype metamaterial that uses electrical signals to control both the direction and intensity of energy waves passing through a solid material.

“The biggest technical challenge was to build up small and stable mechanical and electrical interfaces,” Huang said in an interview with Tech Briefs.

Potential applications include military and commercial uses, such as controlling radar waves by directing them to scan a specific area for objects or managing vibration created by air turbulence from an aircraft in flight.

“This metamaterial has odd mass density,” Huang said. “So, the force and acceleration are not going in the same direction, thereby providing us with an unconventional way to customize the design of an object’s structural dynamics, or properties to challenge Newton’s Second Law.”

This is the first physical realization of odd mass density, Huang noted.

“For instance, this metamaterial could be beneficial to monitor the health of civil structures such as bridges and pipelines as active transducers by helping identify any potential damage that might be hard to see with the human eye.”

The energy exchange between mechanical and electric domains is the key mechanism to realize this novel phenomenon, Huang told Tech Briefs. He added that the next step is to extend the concept to 3D materials.

However, he told Tech Briefs that “this is fundamental research so there are many steps that still need to be completed.”