Adaptive ferrofluidic robotic system with passive component activation capabilities
image: (A) Conceptual diagram of MFR motion control. (i) Conceptual illustration of MFR directional control based on the horizontal rotation of permanent magnets. (ii) Conceptual illustration of MFR deformation control based on the vertical ascension of permanent magnets. (iii) Conceptual illustration of MFR displacement control based on the translational motion of permanent magnets. (C) Conceptual diagram of detailed components of the magnetic control device. The core components include peripheral coils and a spherical permanent magnet, where the rotation of the permanent magnet is controlled by changing the current in the coils. (D) Conceptual diagram where the MFR drives gear movement through deformation and rotation. (E) Conceptual diagram depicting the MFR driving external devices to deliver objects through deformation and displacement. (F) Conceptual diagram illustrating the MFR-based capsule performing targeted drug delivery.
Credit: Zhan Yang, School of Future Science and Engineering, Soochow University.
Magnetically driven microrobots have long been hailed as game-changers for biomedical interventions, from intraocular surgery to on-demand drug delivery. However, conventional systems rely on either a single permanent magnet (unable to generate flexible rotating magnetic fields) or electromagnetic coils (e.g., Helmholtz coils, which produce weak gradient fields and are bulky). “These flaws restrict motion capabilities, limit workspace size, and increase energy consumption—hindering their use in confined clinical settings like blood vessels or the gastrointestinal tract.” Said the author. To address these challenges, we designed a compact, energy-efficient hybrid system that combines neodymium-iron-boron (NdFeB) spherical permanent magnets (SPMs) with four orthogonally arranged electromagnetic coils. “Key breakthroughs include: (1) Spherical Friction Strategy: A steel ball and low-viscosity lubricant reduce friction between the SPM and its semicircular support, enabling the system to drive larger magnets (30mm diameter) and output greater torque while minimizing energy use. (2) Synergistic Control: By programming the bottom-mounted coils to regulate the SPM’s position and rotation, the system generates enhanced magnetic fields and gradients—precisely controlling the MFR’s locomotion, orientation, and shape deformation. (3) Compact Design: The entire actuation system measures just 14×14×10 cm³, with potential for further miniaturization, making it compatible with small-scale mobile medical devices.” said study author Zhan Yang, a professor at Soochow University.
The MFR, crafted from silicone oil-based ferrofluid (Fe₃O₄ nanoparticles modified with phospholipid-polyethylene glycol for biocompatibility). “The MFR show cased remarkable adaptability in rigorous experiments. Precision Motion Control: In a 150mm-diameter glass dish, the MFR followed complex trajectories (e.g., rounded squares, flower-shaped paths) with average positioning errors as low as 0.162mm—far outperforming conventional systems (which typically have errors of 0.3–0.9mm); Deformation for Narrow Spaces: By adjusting the distance between the SPM and MFR (denoted as dₕ), the robot stretched to a maximum aspect ratio of 3.6, allowing it to navigate narrow channels simulating bronchial tubes, bile ducts, and 3D vascular phantoms; Driving Passive Mechanical Systems: The MFR acted as a “power pack” to drive gear mechanisms (weighing up to 15g total) and transport simulated drug particles (43mg microspheres) at an average speed of 14.48mm/s—even delivering a 172mg payload over 90mm in 6 seconds.” emphasized the authors.
A standout application of the MFR is its integration into a drug delivery capsule, designed for precise temporal and spatial control of therapeutic release: (1) Magnetothermal Drug Release: High-frequency magnetic fields trigger the MFR to generate heat, accelerating the dissolution of a gelatin capsule shell. At 45°C (safe for human tissue), the capsule released 50% of its simulated drug payload in just 45 seconds. (2) Selective Vascular Occlusion: The MFR could temporarily block healthy blood vessels upstream of lesions, confining drug diffusion to target areas—a critical advancement for chemotherapy, where up to 62% of conventional doses inadvertently reach healthy tissues.
In summary, this hybrid system expands the functional applications of ferrofluidic robots, making them viable tools for complex clinical scenarios,” said Prof. Yang. “We anticipate it will drive innovations in minimally invasive therapy, drug delivery, and even the removal of ingested foreign objects like button batteries..
Authors of the paper include Qinkai Chen, Haozhe Feng, Xinjian Fan, Hui Xie, Lining Sun, Zhan Yang.
This work has been supported in part by the National Key R&D Program of China under grant 2023YFB 4705300 and the National Natural Science Foundation of China under grants 62422313, 62103294, and 61925304.
The paper, “Adaptive Ferrofluidic Robotic System with Passive Component Activation Capabilities” was published in the journal Cyborg and Bionic Systems on Jun 24, 2025, at DOI: 10.34133/cbsystems.0300.