Professor Osama R. Bilal, an engineering assistant professor at the University of Connecticut, leads a research group exploring how structural geometry can be used to manipulate waves. His team’s latest work presents a programmable metamaterial capable of shifting into more configurations than physicists use to estimate the number of atoms in the universe. The project, developed within the Wave Engineering for eXtreme and Intelligent maTErials laboratory, aims to demonstrate how real-time reconfigurability can enhance the control of sound waves for scientific, industrial, and medical applications.
Keogh, M. R., & Bilal, O. R. (2025). Combinatorial asymmetric acoustic metamaterials with real-time programmability. Proceedings of the National Academy of Sciences, 122(48). https://doi.org/10.1073/pnas.2502036122
The study centres on an array of asymmetric pillars that resemble small apple cores. Each pillar contains one or more concave faces and can be rotated independently by a small motor. The current prototype contains an eleven-by-eleven grid, producing more than a hundred individual elements that can each be adjusted with one-degree accuracy. When sound is projected through the grid, the concave surfaces redirect the waves. Because every pillar can be set to a different angle, the material can create an extremely large range of acoustic pathways.
Professor Osama R. Bilal, assistant professor at the University of Connecticut stated,
“In my mind, this is what UConn is all about. Training young engineers to grow and mature into professional, world-class scientists is one of the most rewarding parts of being a professor.”
The research team reports that this tunability allows the material to shift between functions without requiring a new physical design. It can focus sound to a single point for medical imaging or therapeutic targeting and can disperse sound across a broader area for damping or noise mitigation. The team also demonstrated that the grid can direct sound along its boundaries in a way that mirrors the behaviour of topological insulators, a class of materials that support unidirectional conduction along their edges.
These results stem from an attempt to rethink how metamaterials are built. Traditional metamaterials are fixed and can only perform the function they are designed for during fabrication. Any damage or change in operational requirements can limit their usefulness. In contrast, the UConn material allows its internal structure to be changed repeatedly. Because the motors are electronically controlled, the pillars can be tuned in real time, and the system can be adjusted through software rather than mechanical reconstruction.
The combinatorial nature of the platform extends the design space even further. By moving pillars in coordinated groups, the researchers create “supercells” that produce acoustic effects not achievable with single isolated pillars. This enables additional wave patterns and behaviours that can be selected depending on the application. According to the researchers, the number of possible combinations grows beyond what can be computed by hand. They note that attempting to manually model each configuration would span generations.
Given this complexity, the group is turning to machine learning to help navigate the design space. Their long-term aim is to create a metamaterial that can identify and optimize its own configuration based on performance goals, effectively creating a material that behaves as an autonomous wave-engineering system.
The work also reflects the evolution of the laboratory itself. The collaboration between Professor Bilal and first author Melanie Keogh began when Keogh joined the group as an undergraduate student. Her interest in vibrations and hands-on design led her to build much of the circuitry that controls the platform. The mechanical assembly, which requires precise alignment of the pillars and their motors, became a central component of the project. Keogh’s progression from undergraduate researcher to lead author demonstrates how iterative lab work can prepare engineers for contributions that move well ahead of current industry practice.
The team sees numerous paths for future development. Medical imaging, targeted ultrasound therapy, acoustic tweezers, soundproofing and architectural acoustics all present potential uses. Beyond these applications, the platform offers researchers an opportunity to study fundamental wave physics in a controlled environment. Work is also underway to apply related ideas to aerodynamic drag reduction, where structured surfaces may help lower energy consumption for moving objects.
While additional testing and machine-learning integration remain ongoing, the current results offer a detailed look at a reconfigurable acoustic metamaterial that can operate across an unprecedented number of states. The researchers consider the platform an early step toward materials that can be programmed, reconfigured, and optimized repeatedly across their lifetime.
Adrian graduated with a Masters Degree (1st Class Honours) in Chemical Engineering from Chester University along with Harris. His master’s research aimed to develop a standardadised clean water oxygenation transfer procedure to test bubble diffusers that are currently used in the wastewater industry commercial market. He has also undergone placments in both US and China primarely focused within the R&D department and is an associate member of the Institute of Chemical Engineers (IChemE).
