A New Soft Underwater Robot Swims in 3D With Just Two Pneumatic Actuators

Soft robots usually buy their agility with a mess of pumps, valves, and code. Researchers at North Carolina State University are taking the opposite bet underwater, using a feather star inspired body plan with four elastic wings and only two pneumatic actuators to pull off full 3D maneuvers. The trick is “mechanical intelligence,” letting the shape and springiness of the material do much of the control work as water pushes back. It is still a tethered prototype for now, but the team is already aiming for a wireless, autonomous version built for real-world conditions.

Some of the most interesting robotics work right now is happening far from humanoid demos and warehouse arms. At North Carolina State University, researchers have been watching an unlikely teacher: the feather star, a marine animal that can swim and steer with graceful, multi-directional control. Their new prototype borrows that body logic, then strips the machine down to the basics.

A robot inspired by the ocean’s feathered stars

The team’s underwater robot aims for maneuverability without piling on motors, sensors, or heavy onboard computing. The big idea is to let the body do more of the work. Feather stars coordinate many arms, but the engineers did not try to copy biology piece by piece. Instead, they translated a principle: use structure and timing to unlock multiple motions from a small set of inputs.

This is the case for many autonomous machines today, where additional degrees of freedom often mean more hardware, more control code, and more failure points. Here, the robot’s form is designed to reduce that complexity from the start.

Design and movement engineered with simplicity

Unveiled on October 7, 2026, the soft-bodied prototype uses 4 elastic wings driven by 2 pneumatic actuators. Those wings are not just flippers. Their shape and springiness help define what each pulse of air pressure turns into: lift, forward motion, a turn, or a tight repositioning in place.

In controlled tests, the researchers report peak performance of 1.64 body lengths per second and a maximum rotation rate of 90 degrees per second. Because the speed is normalized to body length, it is a clean way to compare the design even before the team locks in a final size for a deployable version.

Mechanical intelligence, not more AI

The paper leans on a concept often called mechanical intelligence, meaning the robot’s physical properties handle tasks that might otherwise require extra actuators or continuous feedback control. For example, the elastic wings passively snap back after a stroke, so the system does not need a separate command to reset each wing position.

Water flow is part of the mechanism too. Each stroke changes the local currents the next stroke will “feel,” so the robot is designed to take advantage of those fluid interactions rather than fighting them with brute-force control.

What’s missing for real-world autonomy

Right now, the robot is still tethered for power and control, a practical limitation for open-water work. The next step is a wireless, fully autonomous platform with onboard energy, pressure supply, sensors, and tighter control loops, all without losing the simplicity that makes the design appealing.

The research appears in Science Advances as “Minimal-Actuation Feather Star-Inspired Soft Swimmers for Multimodal 3D Maneuverability” (DOI: 10.1126/sciadv.aeg9211). If the team can keep performance while cutting the cord, this kind of soft swimmer could become a useful tool for inspection, environmental monitoring, and small-object retrieval underwater.