This robotic fish represents a convergence of advanced mechatronics, control systems, and underwater communication technologies, resulting in an autonomous device uniquely suited to marine ecosystem inspection and maintenance. Its biomimetic design incorporates flexible fins that mimic natural fish locomotion, allowing for efficient and agile navigation under water. By deploying cutting-edge actuators that replicate fin movements, the robot achieves propulsion with minimal noise and disturbance to aquatic life, a significant advantage over traditional underwater vehicles relying on propellers.

Central to the robot fish’s functionality is its umbilical communication system, facilitating reliable data transmission between the submerged platform and surface control units. This system supports real-time wireless communication, a capability critically tested in recent trials alongside a surface robot at the experimental facilities of Port Castelló. These wireless exchanges enable synchronized operations and remote command execution, essential for intricate tasks such as inspection of sensitive environments or deployment of scientific sensors.

Equipped with an auxiliary sonar system, the robot fish navigates complex underwater terrains and performs detailed mapping of submerged structures. This sonar capability enhances situational awareness, allowing the platform to detect obstacles and features within its operational radius. Coupled with a specialized visual inspection subsystem designed explicitly for the internal examination of fish farm nets, the robot offers unprecedented insights into aquaculture infrastructure health, addressing a crucial need for sustainable aquafarming practices.

The integration of sensor deployment and retrieval mechanisms within the robot opens new frontiers for marine monitoring. By autonomously positioning environmental sensors and subsequently collecting them, the robotic system facilitates long-term data acquisition without extensive human intervention, increasing operational safety and efficiency while reducing costs. This aspect is vital in challenging aquatic environments where traditional sensor maintenance is logistically complex and hazardous.

Professor Raúl Marín, a leading researcher at CIRTESU, emphasizes the importance of incrementally rigorous testing regimes. The developmental pathway began with controlled university lab experiments and progressively extended to real-world marine settings like Port Castelló. This methodological approach ensures that each facet of the technology is validated under increasingly realistic conditions, refining system robustness and performance. Collaborative efforts with Port Authority personnel have been instrumental in this process, enabling access to diverse operational scenarios that simulate actual deployment challenges.

Environmental sustainability and animal welfare in aquaculture are central motivators behind this research. By providing a sustainable, non-invasive platform for inspection and maintenance, the robotic fish minimizes human disturbances to underwater habitats while ensuring the structural integrity of fish farming nets. These advances translate directly into improved animal safety and welfare, as timely detection of net integrity issues prevents escapes and protects farmed species from predation or disease transmission.

Looking ahead, CIRTESU’s strategic roadmap involves enhancing the robot fish’s capabilities to autonomously perform net repairs, a complex task that demands precise manipulation and sophisticated control algorithms. Developing robotic interventions to conduct maintenance operations underwater not only promises to revolutionize aquaculture logistics but also positions the technology as a scalable solution for broader marine infrastructure management.

The collaboration between Universitat Jaume I and the Port Authority of Castelló underscores a shared vision for the port as a living laboratory—a dynamic innovation hub facilitating advanced marine technology experimentation. Since formalizing their partnership in July 2024, the provision of port facilities as an isolated testbed environment has accelerated the transition of technologies from experimental prototypes towards operational readiness, elevating the Technology Readiness Level of CIRTESU’s projects.

Academic contributions underpinning this development include doctoral research led by Andrea Pino Jarque, complemented by supervision from María Rosario Vidal and Raúl Marín Prades, with overall coordination by Professor Pedro J. Sanz Valero. Additionally, the involvement of recent graduates such as Max Puig Sariñena, who contributed to underwater communication experiments, exemplifies the centre’s commitment to integrating educational initiatives with applied research.

The robot fish initiative stands as a testament to the transformative potential of interdisciplinary engineering, combining mechanics, electronics, software, and marine sciences to address real-world challenges. Its success resonates beyond national boundaries, offering a model for future autonomous underwater systems designed for environmental monitoring, infrastructure surveillance, and sustainable aquaculture.

This award-winning project not only elevates the profile of CIRTESU and Universitat Jaume I within the global robotics community but also reflects broader trends toward environmentally conscious automation. As marine industries seek innovative tools to balance productivity with ecological stewardship, technologies like the robot fish are poised to lead a new era of marine exploration and maintenance, fostering a safer and more sustainable aquatic future.

Subject of Research: Advanced biomimetic underwater robotic fish for marine environment monitoring and aquaculture maintenance.

Article Title: Award-Winning Biomimetic Robot Fish Enhances Marine Automation and Sustainable Aquaculture Monitoring at Port Castelló.

News Publication Date: September 2024

Web References: Not provided

References: Not provided

Image Credits: Universitat Jaume I of Castellón

Keywords: underwater robotics, biomimetic design, marine automation, aquaculture monitoring, sensor deployment, wireless underwater communication, sonar inspection, sustainable aquaculture, autonomous marine vehicles, robot fish, Port of Castelló, CIRTESU, Universitat Jaume I

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