Researchers at North Carolina State University have shattered their own record for the fastest swimming soft robot, drawing inspiration from the graceful movements of manta rays to enhance its underwater agility.
“Two years ago, we demonstrated an aquatic soft robot that was able to reach average speeds of 3.74 body lengths per second,” says Jie Yin, corresponding author of a paper on the work and an associate professor of mechanical and aerospace engineering at NC State. “We have improved on that design. Our new soft robot is more energy efficient and reaches a speed of 6.8 body lengths per second.In addition, the previous model could only swim on the surface of the water. Our new robot is capable of swimming up and down throughout the water column.”
the key to this breakthrough lies in the robot’s manta ray-inspired design. Its fins, shaped like those of the majestic sea creature, are made of a material that remains stable when spread wide. These fins are attached to a flexible silicone body containing an air chamber. Inflating this chamber forces the fins to bend, mimicking the downward stroke of a manta ray’s fin.When the air is released, the fins spontaneously snap back into their original position.
“Pumping air into the chamber introduces energy into the system,” explains Haitao Qing, first author of the paper and a Ph.D. 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.”
The team also meticulously studied the fluid dynamics of manta rays to gain precise control over the robot’s vertical movement.
“We observed the swimming motion of manta rays and were able to mimic that behavior in order to control whether the robot swims toward the surface, swims downward, or maintains its position in the water column,” says Jiacheng Guo, co-author of the paper and a Ph.D. student at the University of Virginia. “When manta rays swim, they produce two jets of water that move them forward. Mantas alter their trajectory by altering their swimming motion. We adopted a similar technique for controlling the vertical movement of this swimming robot.We’re still working on techniques that will give us fine control over lateral movements.”
“Specifically, simulations and experiments showed us that the downward jet produced by our robot is more powerful than its upward jet,” says Yuanhang Zhu, co-author of the paper and an assistant professor of mechanical engineering at the University of California, Riverside. “If the robot flaps its fins quickly, it will rise upward. But if we slow down the actuation frequency,this allows the robot to sink slightly in between flapping its fins — allowing it to either dive downward or swim at the same depth.”
“Another factor that comes into play is that we are powering this robot with compressed air,” Qing adds. “That’s relevant becuase when the robot’s fins are at rest, the air chamber is empty, reducing the robot’s buoyancy. And when the robot is flapping its fins slowly, the fins are at rest more often. In other words, the faster the robot flaps its fins, the more time the air chamber is full, making it more buoyant.”
The researchers demonstrated the robot’s capabilities in two ways. first,they successfully navigated a course of obstacles placed on the surface and floor of a water tank. Second, they showcased the untethered robot hauling a payload on the water’s surface, including its own air and power source.
“This is a highly engineered design, but the essential concepts are fairly simple,” Yin says. “And with only a single actuation input, our robot can navigate a complex vertical habitat. We are now working on improving lateral movement, and exploring other modes of actuation, wich will considerably enhance this system’s capabilities.Our goal is to do this with a design that retains that elegant simplicity.”
The paper, “Spontaneous Snapping-Induced Jet Flows for Fast, Maneuverable Surface and Underwater Soft Flapping Swimmer,” is published open access in the journal Science Advances.
This work was supported by the National Science Foundation under grants 2126072 and 2329674; and from the Office of Naval Research under grant N00014-22-1-2616.
## Manta Ray-Inspired Soft Robot Shatters Speed Records: An Expert Interview
**World Today News**: Dr.Yin, congratulations on your team’s groundbreaking achievement in developing a faster and more versatile swimming soft robot. Could you tell us more about this incredible new technology?
**Dr. jie Yin**: Thank you. We’re very excited about the progress we’ve made.Two years ago, our team demonstrated an aquatic soft robot capable of reaching an average speed of 3.74 body lengths per second. this new design, inspired by the elegant movements of manta rays, is significantly more energy-efficient and attains a remarkable speed of 6.8 body lengths per second.
**WTN**: That’s phenomenal! What makes this new robot so much faster than its predecessor?
**Yin**: The key lies in the manta ray-inspired design. By mimicking the shape and mechanics of a manta ray’s fins,we’ve created a system that is both powerful and efficient. These fins are made of a unique material that remains stable when spread wide. They are attached to a flexible silicone body containing an air chamber. Inflating this chamber forces the fins to bend, creating a downward stroke similar to that of a manta ray. When the air is released, the fins naturally snap back into thier original position.
**WTN**: It sounds like a remarkably elegant solution.
**Yin**: It is indeed.
**Haitao Qing, PhD student at NC State**: Pumping air into the chamber introduces energy into the system. As the fins strive to return to their stable state, releasing the air converts that stored energy, propelling the robot forward.
**WTN**: That’s fascinating. So, you only need a single actuator to control the entire movement?
**Qing**: Exactly. This simplifying design makes the robot more responsive and allows for rapid actuation,contributing to its impressive speed.
**WTN**: Your team mentions that this new robot is capable of swimming throughout the water column. How did you achieve this increased versatility?
**Yin**: Apart from the flapping motion, we also meticulously studied the fluid dynamics of manta rays to gain precise control over the robot’s vertical movement. observing their
swimming patterns helped us fine-tune the fin design and air pressure adjustments for controlled ascents and descents.
**WTN**: This is truly remarkable progress. What are the potential applications for this technology?
**yin**: This technology has a wide range of potential applications, from environmental monitoring and underwater exploration to medical procedures and search and rescue operations.
Its agility,speed,and adaptability make it a promising tool for tasks that require precise maneuvering and navigation in challenging aquatic environments.
**WTN**: Thank you, Dr.Yin and mr. Qing, for sharing your insights on this groundbreaking research.
We’re carefully watching the progress you make as you continue to push the boundaries of soft robotics.
