A smart materials model that defies Newton’s laws of motion

An innovative metamaterial with unconventional properties uses electrical signals to control the direction and intensity of energy waves traversing a solid. This innovative metamaterial, which has a single mass density, offers a departure from Newton’s second law, in that force and acceleration do not go in the same direction. Huang envisions wide-ranging applications from military and commercial uses, such as controlling radar waves or managing vibrations from air turbulence in aircraft, to civilian uses such as monitoring the health of structures such as bridges and pipelines.

University of Missouri researchers have designed a prototype of a small, lightweight energetic metamaterial that can control the direction and intensity of energy waves.

Professor Guoliang Huang of the University of Missouri has developed a prototype metamaterial that can control the direction and intensity of energy waves using electrical signals. The innovative material has potential applications in the military and commercial sectors, and can also be used to monitor the structural health of bridges and pipelines.

For more than 10 years, Guoliang Huang, Huber and Helen Croft Chair in Engineering at the University of Missouri, has been researching the unconventional properties of “[{” attribute=””>metamaterials” — an artificial material that exhibits properties not commonly found in nature as defined by Newton’s laws of motion — in his long-term pursuit of designing an ideal metamaterial.

Huang’s goal is to help control the “elastic” energy waves traveling through larger structures — such as an aircraft — without light and small “metastructures.”

The prototype metamaterial uses electrical signals transported by these black wires to control both the direction and intensity of energy waves passing through a solid material. Credit: University of Missouri

“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.”

Guoliang Huang. Credit: University of Missouri

Now, Huang’s one step closer to his goal. In a new study published in the Proceedings of the National Academy of Sciences (PNAS) on May 18, Huang and 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.

Potential applications of his innovative design 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 said.

“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.”

Reference: “Active metamaterials for realizing odd mass density” by Qian Wu, Xianchen Xu, Honghua Qian, Shaoyun Wang, Rui Zhu, Zheng Yan, Hongbin Ma, Yangyang Chen and Guoliang Huang, 18 May 2023, Proceedings of the National Academy of Sciences.
DOI: 10.1073/pnas.2209829120

Other MU contributors include Qian Wu, Xianchen Xu, Honghua Qian, Shaoyun Wang, Zheng Yan and Hongbin Ma. Grants from the Air Force Office of Scientific Research and the Army Research Office funded the research.