Researchers at Zhejiang University in China recently made huge strides. For example, they’ve created a compact, flexible electromagnetic fin that allows robotic swimmers to move through water with extraordinary efficiency. Research team leader, assistant professor Fanghao Zhou, successfully piloted the bionic fin in water for the first time. Overall, they set a remarkable mass-normalized peak thrust of 0.493 newtons per kilogram, all while maintaining a very light design at just 17 grams.
The team utilized advanced tools, including a high-speed camera and precision force sensors, to measure the fin’s trajectory and the thrust it generated. This study seeks to create robotic approaches to unique flexible, agile, adaptive properties that fish inherently possess. Zhou emphasizes the challenges of replicating these qualities robotically, noting, “Fish are agile, efficient, and adaptive—and robotically mimicking these qualities is a challenge.”
Thanks to the combination of these two small coils and spherical magnets, the innovative fin is able to deliver both flexibility and power. This design addresses a common problem with robotic fins. Though traditional motor-powered fins provide powerful thrust, they tend to be large and inflexible. Zhou states, “Traditional robotic fins powered by motors can generate strong thrust, but they’re often bulky and rigid. Soft actuators, on the other hand, are flexible but usually too weak to be practical. Our goal was to combine the best of both fields—a compact actuator that’s powerful yet flexible, like real muscle.“
Zhe Wang, a graduate student in Zhou’s lab, was instrumental in the research. He created a math model that accurately connects electrical power input to hydrodynamic thrust output. The resulting robotic swimmer is capable of making tight turns over an area equivalent to only 0.86 body-length radius, showcasing its unparalleled agility underwater. Wang notes, “Our next step is to study multi-fin coordinated motion, enabling the robot to perform more flexible and lifelike swimming behaviors.”
The team’s research resulted in astounding performance with a maximum swimming speed of 405 millimeters or 1.66 body lengths per second. This innovation paves the way for additional innovations in multi-fin systems, creating the potential to increase the versatility of robotic swimmers exponentially. Zhou cautions that because the electromagnetic coils consume a lot of current, the robot’s swimming time must be limited.