The quest to simultaneously suppress unwanted noise and maintain air circulation has fueled extensive research for years. Traditionally, acoustic silencers achieve narrowband sound attenuation by relying on resonant mechanisms tuned to specific frequencies. However, these conventional designs falter in real-world scenarios where noise spans a broad spectrum of frequencies and fluctuates unpredictably. The innovation brought forth by the Zhang Lab breaks this paradigm by leveraging advanced phase-gradient metamaterials, a class of artificially engineered structures designed to manipulate acoustic waves with extraordinary precision.

At the heart of their approach is the creation of ultra-open metamaterial architectures—structures featuring intricately designed rectangular and cylindrical elements that permit substantial airflow while still delivering high-performance noise cancellation. This balance is critical for applications ranging from HVAC systems and industrial ventilation to transportation hubs and open-plan offices, where persistent airflow is essential but noise levels must be carefully managed. The PGUOM designs draw upon complex computational simulations to fine-tune the metamaterial phase gradients, enabling broadband sound silencing that adapts dynamically to changing acoustic environments.

One of the key breakthroughs in their work is overcoming the typical trade-off between peak silencing efficiency and bandwidth. Conventional designs achieve high noise attenuation only within narrow frequency bands, but the PGUOM achieves a broad spectrum of silencing, akin to noise-canceling headphones that adjust to a range of sounds in real-time. This is enabled by their use of phase gradient control—precisely shifting the phase of incoming sound waves—to cause destructive interference across a wide frequency band. Consequently, this metamaterial provides robust noise suppression even as sound pitch and amplitude vary, a feature that dramatically broadens its practical utility.

From a structural perspective, the PGUOM’s ultra-open configuration is more than a design choice; it is a functional necessity. Unlike conventional dense materials, which impede airflow and degrade system efficiency, these open metamaterials maintain ventilation while achieving impressive acoustic performance. Importantly, samples of these metamaterials were fabricated using advanced commercial 3D printing techniques, demonstrating their feasibility for scalable manufacturing and potential integration in diverse engineering systems.

This research builds on the Zhang Lab’s legacy in acoustic metamaterial silencers, an area where they have consistently pushed the boundaries of physics and engineering. Their early work, dating back to 2019, focused on sound shields that harnessed Fano resonance effects to block narrowband noise sources while preserving airflow. These initial findings proved critical in environments such as fan and propeller systems, where targeted noise reduction was needed without obstructing ventilation channels.

Extending beyond these foundations, the team’s current work embraces multi-band, broadband, and tunable acoustic silencing strategies, making the technology highly adaptable to multifaceted noise challenges. The intelligent design of the PGUOM reflects a nuanced understanding of acoustic wave propagation and reveals how artificial material structuring can augment or suppress sound in unprecedented ways. Their computational models simulate realistic conditions, mapping how sound waves interact with the metamaterial at different frequencies and angles, ensuring reliable performance in chaotic soundscapes.

Professor Xin Zhang emphasizes that the PGUOM represents a “smarter approach” to noise control—akin to having active noise-canceling headphones built into the environment itself. This capability is especially valuable in dynamic and open spaces where sound sources are numerous and varied, rendering traditional silencers ineffective. The metamaterial’s broadband capability ensures continuous sound suppression despite fluctuating noise characteristics, offering a new paradigm for sound management in public and industrial settings.

Beyond the technical merits, the project also carries significant societal implications. Noisy industrial environments, crowded offices, and bustling transportation centers all contribute to noise pollution, which is linked to a range of health and productivity issues. Innovations like the PGUOM open pathways to quieter, healthier spaces while maintaining essential ventilation, thereby supporting both environmental comfort and operational efficiency.

From a commercialization standpoint, the research team has already moved to secure intellectual property rights surrounding their invention. A U.S. provisional patent application was filed, followed by an international PCT application, underscoring the novelty and potential market impact of their phased array ultra-open metamaterial technology. These legal protections pave the way for collaboration with industry partners interested in integrating these metamaterials into next-generation acoustic management solutions.

Looking forward, ongoing efforts will likely focus on refining the metamaterial structures for specific industrial applications, scaling up fabrication techniques, and conducting real-world trials to validate performance under operational stresses. The intersection of computational modeling, additive manufacturing, and experimental validation in this research exemplifies how interdisciplinary collaboration drives innovative technology development.

In summary, the PGUOM developed by the Zhang Lab represents a landmark achievement in acoustic metamaterial research, combining theoretical rigor with practical applicability. By innovating phase-gradient control in ultra-open structures, the team has unlocked a versatile, broadband approach to acoustic silencing that maintains airflow—a balance previously elusive to engineers and scientists alike. As this technology matures, it promises to redefine standards for noise control across multiple sectors, enhancing human environments with elegant scientific solutions.

Subject of Research: Not applicable

Article Title: Phase gradient ultra open metamaterials for broadband acoustic silencing

News Publication Date: 1-Jul-2025

Web References:
https://www.nature.com/articles/s41598-025-04885-6

References:
DOI: 10.1038/s41598-025-04885-6

Image Credits:
Photo courtesy of Zhiwei Yang and Xin Zhang.

Keywords

Acoustics, Physical sciences, Material properties, Engineering

The core of Zhang’s innovation lies in the engineering of a metamaterial—a composite fabricated with meticulously designed microstructures that endow it with acoustic behaviors not found in conventional materials. Unlike ordinary solids, this metamaterial possesses a finely patterned sawtooth surface structure that interacts with incident sound waves in special and controllable ways. By adjusting the acoustic fields emitted by surrounding speakers, the material can experience differing radiation forces, allowing it to push, pull, and even rotate objects in fluid environments with unprecedented precision.

Sound waves have long been exploited for underwater applications, including sonar mapping of the seafloor and non-invasive medical treatments like lithotripsy. However, harnessing these waves to achieve direct manipulation of objects remotely has remained a challenging endeavor. Zhang’s approach circumvents these difficulties by embedding the metamaterial on the target objects. When the tailored acoustic waves strike the metamaterial surface, they create localized differences in pressure and radiation force, effectively “grabbing” and moving the object without any mechanical attachment.

One of the unique challenges addressed by Zhang stems from fabricating underwater metamaterials that combine the right structural intricacies with the necessary acoustic impedance contrasts. Conventional manufacturing techniques either fall short in resolution or demand prohibitively high costs. To overcome these obstacles, Zhang developed an innovative low-cost fabrication method that achieves remarkable precision while producing material surfaces with a large acoustic impedance difference relative to water. This disparity is crucial for generating strong acoustic forces and precise control.

The functionality of Zhang’s metamaterial was extensively tested on a variety of objects immersed in water, including items made of wood, wax, and plastic foam. By affixing the material patch onto these objects, he demonstrated the ability to manipulate them three-dimensionally—pushing, pulling, and rotating them solely through carefully modulated acoustic fields. This non-contact manipulation method hints at applications ranging from delicate underwater assembly tasks to the control of small underwater robotic vehicles.

Beyond underwater robotics, the implications for medical science are profound. Human tissue is predominantly composed of water, and this similarity suggests that Zhang’s acoustic metamaterial technology could pave the way for novel forms of remote surgery or targeted drug delivery. By fine-tuning sound waves, medical devices or therapeutic agents could be manipulated precisely inside the body without invasive procedures, reducing risk and increasing efficacy.

Zhang emphasized the broad potential of this technology, stating that his metamaterial method provides a reliable means to apply different acoustic radiation forces on various objects in liquid media. This could transform the way engineers and medical professionals conceive underwater tools and in-body devices, enabling levitation, actuation, and complex manipulations previously thought impossible outside robotic grippers or direct mechanical operations.

Despite the successful demonstrations, Zhang acknowledges that achieving these capabilities was not trivial. The inherent complexities of underwater environments and the stringent demands on material properties make designing and fabricating suitable metamaterials an exacting task. Through his inventive fabrication process, he was able to reconcile these demands, producing metamaterials that are not only effective but also scalable and cost-efficient.

Looking forward, Zhang is working to refine his metamaterial designs into smaller, more flexible patches. Such developments could vastly enhance maneuverability and integration into diverse environments, from compact medical instruments navigating within the body to compact underwater systems managing fragile tasks in tight spaces. The modular and tunable nature of the metamaterial approach points toward customizable solutions serving a wide array of future technological needs.

This research heralds a transformative shift in acoustic manipulation paradigms, moving from theoretical concepts to practical applications. Remote manipulation without physical contact is no longer the stuff of science fiction. Instead, it is rapidly becoming a practical tool backed by fundamental physics, advanced materials engineering, and sophisticated acoustic control systems.

By enabling precise, remote force generation in liquid media, Zhang’s acoustic metamaterials set the stage for multidisciplinary innovations. Underwater exploration, environmental monitoring, industrial processing, and minimally invasive medical procedures stand to benefit significantly. The ability to perform complex object movements and orientations remotely could reduce human risk, increase operational efficiency, and unlock new experimental possibilities.

In sum, Dajun Zhang’s work exemplifies the power of integrating acoustic science with metamaterial engineering to surmount longstanding challenges in underwater manipulation. As this technology matures, it promises to revolutionize how humanity interacts with submerged objects and biological environments, ushering in a new era of contactless, sound-driven control.

Subject of Research: Underwater acoustic metamaterials for remote manipulation of objects

Article Title: Remotely Moving Objects Underwater Using Acoustic Metamaterials

News Publication Date: May 20, 2025

Web References:

• https://acoustics.org/asa-press-room/
• https://acoustics.org/lay-language-papers/
• https://acousticalsociety.org/
• https://www.icacommission.org/

Image Credits: Dajun Zhang

Keywords

Acoustics, Physics, Applied acoustics, Underwater acoustics