Soft Robot Inspired by Manta Rays Sets New Speed Record

Researchers develop a more efficient soft robot capable of swimming faster and exploring complex underwater environments.

A team of researchers from North Carolina State University has unveiled an improved aquatic soft robot, setting a new benchmark for speed and efficiency in soft robotic systems. Inspired by manta rays, the updated robot achieves a remarkable 6.8 body lengths per second—nearly doubling its predecessor’s speed of 3.74 body lengths per second.

“This is a highly engineered design, but the fundamental concepts are fairly simple,” explains Jie Yin, associate professor of mechanical and aerospace engineering at NC State and corresponding author of the study published in Science Advances. “With only a single actuation input, our robot can navigate a complex vertical environment.”

The previous iteration of the robot was confined to the surface of the water. The new design, however, can dive and ascend within the water column, demonstrating greater versatility for potential applications.

Biomimicry in Design

The soft robot mimics the swimming mechanics of manta rays, using flexible fins and a silicone body to propel itself through water. The system’s core innovation lies in its single-actuation mechanism powered by compressed air. The fins are held in a stable position but bend downwards when the air chamber within the robot’s body is inflated, mimicking a manta’s downstroke. When the air is released, the fins snap back, generating the energy needed for propulsion.

“Pumping air into the chamber introduces energy into the system,” says Haitao Qing, lead author and PhD student at NC State. “The fins want to return to their stable state, so releasing the air also releases the energy in the fins. That means we only need one actuator for the robot and allows for more rapid actuation.”

By studying the fluid dynamics of manta rays, researchers also developed methods to control the robot’s vertical movement. “We observed the swimming motion of manta rays and were able to mimic that behaviour in order to control whether the robot swims toward the surface, swims downward, or maintains its position in the water column,” explains Jiacheng Guo, a co-author from the University of Virginia.

Versatility and Future Directions

The robot’s capabilities were demonstrated in two significant tests. First, it successfully navigated an obstacle course submerged in a water tank, showcasing its agility. Second, it hauled a payload across the water’s surface, carrying its own air and power source—a significant step towards untethered underwater robotics.

However, the research team acknowledges there is still work to be done. Lateral movement, for example, remains an area for future improvement. “We’re still working on techniques that will give us fine control over lateral movements,” Guo adds.

“Another factor that comes into play is that we are powering this robot with compressed air,” Qing says. The buoyancy of the robot changes with the air chamber’s state, enabling it to adjust its depth dynamically.

The team is now focusing on enhancing lateral manoeuvrability and exploring other actuation methods. “Our goal is to do this with a design that retains that elegant simplicity,” Yin states.

This advancement in soft robotic design has broad implications, from marine biology studies to underwater exploration and environmental monitoring. The ability to operate in both surface and subsurface environments opens new possibilities for untethered robots in complex aquatic settings.

By leveraging biomimetic principles and simplified engineering, the researchers have created a platform that bridges scientific curiosity and practical utility. As underwater robotics continues to evolve, innovations like these are likely to inspire further breakthroughs across research fields.