The development of autonomous underwater vehicles is on the cusp of a paradigm shift. Whilst traditional systems typically rely on propeller drives and rigid steering mechanisms, nature is increasingly becoming the focus of research as a model. A recent example comes from Northwestern Polytechnical University in Xi’an: there, a robotic fish has been developed that sets new standards in terms of manoeuvrability – whilst drawing on a surprisingly simple design logic.
At the heart of the development is the replication of the so-called knifefish, in particular the white-browed knifefish. This species is characterised by an extraordinary locomotion strategy: instead of undulating its entire body, it uses a single, ribbon-like fin along the underside of its body. It is precisely this principle that has now been adapted for technical use.
One fin, maximum control
The key innovation of the system lies in the use of a single continuously oscillating fin that generates variable thrust. According to the researchers led by Ze-Jun Liang (published in the journal Ocean, 2026), this structure enables highly dynamic adjustment of movement – both in terms of speed and direction.
The robo-fish can thus navigate extremely tight turns, abruptly change direction and remain stable in the water at the same time. It is particularly noteworthy that the body itself is largely rigid in construction. The complexity of the movement is entirely shifted to the fin mechanism.
This decoupling of structure and movement brings significant advantages: the mechanical design is simplified, whilst manoeuvrability increases. Compared to conventional underwater robots, which rely on multiple moving components, the technical complexity is significantly reduced.
Hydrodynamic efficiency through biomimicry
The operating principle is based on wave-like propulsion along the fin. By specifically varying the frequency, amplitude and wavelength of the fin movement, the robo-fish can generate different thrust profiles. This allows not only forward movement, but also precise hovering, backward movement or lateral manoeuvring.
This form of locomotion is considered particularly energy-efficient. Whilst propeller drives often generate turbulence and cause energy losses, the fin movement makes optimal use of hydrodynamic effects. The result is a quiet, low-turbulence propulsion system – a decisive advantage for applications in sensitive environments.
Relevance for safety and industrial applications
The development is not only interesting from a biological or robotic perspective, but also has concrete implications for the safety and industrial sectors. Autonomous underwater vehicles are increasingly being deployed in critical infrastructure – for example, to inspect pipelines, port facilities, offshore wind farms or subsea cables.
High manoeuvrability is crucial, particularly in complex or hard-to-access environments. Conventional systems often reach their limits here, for instance in tight spaces or when navigating in turbulent currents. A robo-fish with such precise controllability could overcome these limitations.
Added to this is the advantage of low noise levels. In safety-critical scenarios – such as surveillance tasks or military applications – movement that is as inconspicuous as possible is of great importance.
Simplified design, scalable systems
Another aspect of the development lies in the comparatively simple construction. As the robot’s body remains largely rigid, the need for complex joint structures or elaborate seals is reduced. The entire movement dynamics are generated by the fin, which acts as the central functional element.
This opens up new possibilities for scaling such systems. Smaller, more cost-effective units could be deployed in swarms to monitor larger areas or collect data. At the same time, larger systems can be developed for industrial applications without the complexity increasing exponentially.
A step towards adaptive robotics
The development of the robo-fish exemplifies just how significantly biomimetic approaches can transform robotics. Instead of optimising existing technical concepts, the functioning of natural systems is directly transferred – often with surprisingly efficient results.
In this specific case, the reduction to a single fin does not lead to limitations, but to a new quality of motion control. The ability to vary thrust flexibly and control movements precisely makes the Robo-Fish a promising approach for future underwater technologies.
Conclusion
The Robo-Fish developed by Northwestern Polytechnical University exemplifies a new generation of autonomous systems: efficient, adaptable and functionally reduced. By consistently drawing inspiration from biological models, it is possible to reduce technical complexity whilst simultaneously increasing performance.
This opens up new prospects for applications in security, industry and environmental monitoring. Biomimetic robots could play a decisive role in the future, particularly in areas where conventional systems reach their limits.
