"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." To guide this optimization, the team developed a fully coupled magnetic‑fluid‑solid multiphysics simulation model in COMSOL, which significantly reduced costly trial‑and‑error experiments. The simulation revealed that the combination of a rapid, large‑amplitude contraction and a carefully tuned glide phase—during which the robot maintains a streamlined bell shape—maximizes the fluid load in the forward direction while minimizing drag. The result is a soft robot that, despite being negatively buoyant with a density over 0.4 g/cm³ higher than water, rockets upward at 14.85 BL/s. "This is substantially faster than previously reported jellyfish‑inspired robots, some of which peak around 10 BL/s," notes Professor Lining Yao, the other corresponding author. "And crucially, we achieve this without any auxiliary buoyancy structures, which would add drag and reduce spatial efficiency."
Beyond straight vertical swimming, the J‑MSR demonstrates remarkable multimodal maneuverability. By programming the internal magnetization pattern during fabrication and using a three‑axis Helmholtz coil system to generate arbitrary field vectors, the robot can swim at large angles from 0° to 122°, roll, climb slopes, cross narrow slits, and even follow S‑shaped trajectories. In an ex vivo pig stomach model, the team showed that switching between modes is essential: when the robot tried to cross gastric folds using only rolling, it failed, but by first floating upward, then swimming horizontally, it succeeded. "This ability to transition seamlessly between floating, horizontal swimming, descending, and anchoring is critical for navigating the unstructured, confined environments inside the human body," says Professor Cao.
What truly sets the J‑MSR apart is its capacity to carry out multiple practical functions while swimming. The robot's central region features a 10‑mm circular cavity that can accommodate various payloads without compromising propulsion. In one demonstration, the robot was equipped with a light‑emitting diode and a receiving coil. Under dual‑frequency magnetic actuation—a low frequency for swimming and a high frequency for wireless power—the J‑MSR flashed like a bioluminescent jellyfish while dynamically suspending or floating upward. "This mimics the way real jellyfish use light to attract prey, and it shows how we can add wireless power and signaling without adding batteries or wires," explains Professor Yao. In another demonstration, the team integrated a variable‑density device containing a low‑boiling‑point liquid and a copper foil. When a high‑frequency magnetic field heated the foil, the liquid vaporized, inflating a soft shell and reducing the robot's density below that of water. The J‑MSR could then clamp onto an underwater object, trigger the phase transition, and ascend while securely holding the object—an efficient "swim‑and‑carry" capability rarely seen in soft microrobots.
For biomedical applications, the researchers attached a polylactic acid microneedle to the central cavity. In an ex vivo pig stomach under ultrasound guidance, the J‑MSR navigated toward a pre‑placed hemostatic clip marker and successfully penetrated the tissue. Quantitative bench tests showed a targeting precision of 4.4 ± 1.85 mm relative to a 10×10 mm microneedle footprint. "This is a concrete step toward magnetically guided drug delivery or biopsy in the gastrointestinal tract," says Professor Cao. Finally, the team integrated a binocular capsule endoscope with two vision sensors. In a stomach model marked with letters A through F, the J‑MSR tilted up to 21.8 degrees—impossible for traditional magnetic capsule endoscopes that rely on static fields—and captured all markers by coordinated floating and horizontal swimming. "Our robot actively reorients itself to eliminate blind spots, which could greatly improve the efficiency of gastric examinations," adds Professor Yao.
The authors acknowledge current limitations, including the need for fully three‑dimensional simulations, machine‑learning‑based waveform optimization, and closed‑loop autonomous control. Nevertheless, the J‑MSR represents a major advance: a single soft robot that is ultrafast, multimodally mobile, and functionally versatile. "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," concludes Professor Cao.
Authors of the paper include Yuxuan Sun, Ruiqi Liu, Chiyuan Ma, Jingyang Liu, Semina Yi, Junnan Gu, Liangyu Xia, Haitao Qing, Kailin Cai, Liang Li, Lining Yao, and Quanliang Cao.
This work was supported by the National Natural Science Foundation of China (52422701 and 524B2095) and the Fundamental Research Funds for the Central Universities (YCJJ20241404).
The paper, "Jellyfish-Inspired Ultrafast and Versatile Magnetic Soft Robots for Biomedical Applications" was published in the journal Cyborg and Bionic Systems on Apr. 3, 2026, at DOI: 10.34133/cbsystems.0540.
