A new jellyfish-inspired soft robot can move through water at record speeds while carrying out complex biomedical tasks, thanks to a magnetic actuation system and optimized motion waveforms designed by researchers.

The device, called the Jellyfish Magnetic Soft Robot (J-MSR), is built to replicate how real jellyfish move through coordinated contraction and relaxation. Instead of using onboard power, it is controlled externally using magnetic fields, allowing it to remain lightweight and flexible while still achieving high-speed propulsion in fluid environments.

To improve performance, the team modeled the system using a fully coupled magnetic-fluid-solid simulation in COMSOL. This allowed them to fine-tune multiple parameters, including magnetic flux density and timing phases of motion. The goal was to reduce drag and increase forward thrust without relying on bulky buoyancy systems.

The optimization approach focused on creating an asymmetric motion pattern similar to natural jellyfish, where the contraction phase is faster than recovery. This imbalance helps push more fluid backward while maintaining stability during glide phases, improving overall efficiency.

“Natural jellyfish swim by creating both spatial and temporal asymmetries—their contraction phase is faster and sweeps a larger area than the recovery phase,” explains Professor Quanliang Cao, corresponding author of the study.

“We mimicked this strategy using an asymmetric trapezoidal magnetic field waveform, but we went beyond simple emulation. We systematically optimized six waveform parameters, including the positive and negative magnetic flux densities and the durations of the preload, contraction, glide, and recovery phases.”

Engineered motion control

With optimized waveforms in place, the robot achieved a swimming speed of 14.85 body-lengths per second, even though it is negatively buoyant and denser than water by more than 0.4 g/cm³. The design avoids auxiliary buoyancy structures, which typically increase drag in soft underwater robots.

“We believe this platform will open new possibilities for minimally invasive diagnosis and treatment, from gastric inspection to targeted drug delivery, all without onboard power or tethering,” says Professor Cao.

The system also demonstrated performance improvements over earlier jellyfish-inspired robots, some of which reach around 10 body-lengths per second. Researchers say the gain comes from the combination of rapid contraction and a carefully tuned glide phase that reduces resistance.

“And crucially, we achieve this without any auxiliary buoyancy structures, which would add drag and reduce spatial efficiency,” said Professor Lining Yao.

Multi-mode navigation shift

Beyond speed, the J-MSR can switch between multiple movement modes. By adjusting internal magnetization patterns and using a three-axis Helmholtz coil system, the robot can move at angles ranging from 0° to 122°, roll, climb slopes, and navigate tight or curved paths.

In tests using an ex vivo pig stomach model, the robot demonstrated that different motion modes were essential for navigating complex internal structures. Rolling alone failed in narrow folds, but combining vertical floating with horizontal swimming allowed successful traversal.

The robot also integrates a central 10 mm cavity for payloads such as sensors or medical tools. In demonstrations, it carried LEDs, wireless coils, and microneedles without losing propulsion efficiency.

Powerless precision control

The researchers also showed wireless powering and functional activation using dual-frequency magnetic fields. Low-frequency fields controlled movement, while high-frequency fields enabled onboard functions such as heating or signal generation.

In one experiment, a variable-density system allowed the robot to temporarily inflate and change buoyancy using vaporization of a low-boiling liquid. This enabled it to clamp onto objects and then rise while carrying them.

In biomedical tests, a microneedle attached to the robot achieved a targeting accuracy of 4.4 ± 1.85 mm in a stomach model. The system also worked with a capsule endoscope setup, tilting up to 21.8 degrees to capture multiple viewing angles inside a gastric environment. Researchers say future work will focus on fully 3D control, machine learning-based optimization, and closed-loop autonomous navigation for medical use.

The study highlights how soft robotics can combine fluid dynamics, magnetic control, and biomedical functionality into a single platform without onboard power.

The paper, “Jellyfish-Inspired Ultrafast and Versatile Magnetic Soft Robots for Biomedical Applications,” was published in Cyborg and Bionic Systems.