Multi-section magnetic soft robot with multirobot navigation system for vasculature intervention

A research paper by scientists at the University of Macau proposed a novel multi-section magnetic soft robot maneuvered by an associated collaborative multirobot navigation system with magnetic actuation and ultrasound guidance for intravascular intervention.

The new research paper, published on Nov. 28, 2024 in the journal Cyborg and Bionic Systems, provided a versatile magnetic soft robot along with a navigation system to complete the interventional procedure with the vasculature, e.g., embolization elimination.

“Cardiovascular interventional surgery conventionally utilizes a manually steered cable-driven catheter to deliver the drugs/stent to the lesion region of interest, such as thrombus and aneurysm, under the guidance of X-ray fluoroscopy imaging. This method requires surgeons to have high manipulation skills, and the damage from radiation exposure,” explained study author Qingsong Xu, a professor at the University of Macau.

In the past decade, the emerging field of magnetic soft robots has evolved transluminal minimally invasive surgery due to their miniaturization and non-contracting teleoperated magnetic control. “The researchers in this emerging field attempted to apply magnetic soft robots to intraluminal and endovascular surgical procedures, e.g., cardiac ablation, embolization therapy, bioprinting, colonoscopy, and drug deliver,” said study authors. However, current magnetic soft robots suffer from the drawbacks of single curvature and the incompetence of challenging multi-bifurcation steering.

Inspired by concentric tube robots (CTRs), this research aims to design novel multi-section magnetic soft robots with telescopic motion to form various shape configurations, which is designed to facilitate the complex endovascular steering environment under the actuation of an external magnetic field. The newly designed magnetic soft robot is composed of two segments, namely, Tube-I and Tube-II. The cannula tubes are made of polydimethylsiloxane (PDMS) material, which has a soft interaction with the vascular wall. Besides, the outer diameter of Tube-I and Tube-II are 1.8 and 3.5 mm, respectively. “The special design of the magnetic soft robot can steer in the multi-bifurcation vascular system by telescoping the tube with appropriate outer diameter to fit the size of the targeted blood vessel,” said Xu.

The magnetic soft robots are deflected into different curvatures by the magnetic force/torque generated by the magnetic actuation system. This study derives the kinematic and dynamic models of multi-section magnetic soft robot while considering the interaction of the heterogeneous magnetic field generated by the external mobile magnet. Considering computational efficiency while performing intraoperative modeling, the study authors adopt the Cosserat rod theory to model the shape characteristic of the proposed magnetic soft robot. “We also compute the deflection of magnetic soft robot using finite element method (FEM) through the FEM software with approximately 24,000 trigonal elements for each configuration to determine a stable robot poses under a magnetic field with different orientations,” said Xu.

Another challenge is the development of magnetic navigation systems. Magnetic navigation systems (MNS) are important magnetic field generation sources for the magnetic soft robots’ actuation. They are generally classified into two categories, i.e., stationary and mobile configurations. Mobile MNS utilizes multiple fixed electromagnetic coil/permanent magnets to actuate magnetic robots, especially micro-robots. “Such an actuation system suffers the drawbacks of limited workspace and relatively large scale when applied in the surgical field. Mobile MNS has a more promising application due to its long-range motion, high dexterity, and movability” said Xu, Multirobot configuration of surgical robots has proved successful in many surgical applications which can be exploited to develop a versatile magnetic navigation system with both actuation and imaging tracking functionalities.

The study provides a novel collaborative multirobot navigation system with three main components, namely, MUNM: a mobile ultrasound navigation manipulator integrates a ultrasound probe and a force/torque sensor to the distal end of a serial manipulator to realize the magnetic soft robot’s tracking and constant force interaction model; MMAM: a mobile magnetic actuation manipulator integrates a cylindrical axially magnetized permanent magnet on the end-effector of a serial manipulator to provide a rotating external magnetic field; MLAM: the mobile linear advancement manipulator is an advancement module embedded with linear actuation units to realize the telescopic motion of multi-section magnetic soft robot using two separate lead screw drivers. The study author also proposed a quadratic programming (QP)-based optimization scheme to synchronize the hierarchical motion of collaborative multirobot navigation system.

To validate the effectiveness of the study, several experiments were conducted with clinical-relevant environment. First, the kinematic modeling and dynamic characteristics of multi-section magnetic soft robot were verified along with the free-end deflection test. Then, a follow-the-lead dexterity test of multi-section magnetic soft robot inside a 3D sequential-ring scene is conducted. Finally, the study author conducts in vitro experiments to steer the multi-section magnetic soft robot through a biological gelatinous phantom with the guidance of collaborative multirobot navigation system. Experimental results demonstrate that the proposed magnetic soft robot can be successfully navigated within the multi-bifurcation intravascular environment with a shape modeling error 3.62 ± 1.28° and a tip error of 1.08 ± 0.45 mm under the actuation of a collaborative multirobot navigation system through in vitro ultrasound-guided vasculature interventional tests.

“Overall, our key contribution is the effective and precise analytical modeling for both multi-section magnetic soft robot and collaborative multirobot navigation system. The successful validations have solidified the potential of medical applications for future intravascular procedures,” said Xu, explaining that future work may focus on considering the friction and the interaction model with the vasculature tissue, a new material design of coating could be considered in the future design, and enhancing the method by applying a high-level ultrasound imaging algorithm, e.g., deep learning-based vessel segmentation.

Authors: Zhengyang Li and Qingsong Xu

Title of original paper: Multi-Section Magnetic Soft Robot with Multirobot Navigation System for Vasculature Intervention

Journal: Cyborg and Bionic Systems

DOI: 10.34133/cbsystems.0188

About Zhengyang Li:

Zhengyang Li received the B.S. and M.S. degrees in mechatronics engineering from State Key Laboratory of Robotics and System, Harbin Institute of Technology, Harbin, China, in 2016 and 2018, respectively. He received the Ph.D. degree in electromechanical engineering, Faculty of Science and Technology, University of Macau, Macau SAR, China, in 2025. He was a visiting scholar with Technische Universitat Munchen, Munich, Germany, and Universitatsklinik Balgrist Hospital, Zurich, Switzerland. He is a member of Robotics and Automation Society (RAS) and Industrial Electronics Society (IES), IEEE. He is a member of the American Society of Mechanical Engineers (ASME). His current research interests include imaging-guided surgical robots, bio-inspired robots, soft/miniature robots and learning-based automatic control. He is the winner of IEEE ICRA 2024 Best Paper Award Finalist of Medical Robots and IEEE ICDL 2023 Best Conference Paper Award. He served as a reviewer for several journals and conferences of IEEE.

About Qingsong Xu:

Qingsong Xu is currently a Full Professor of Electromechanical Engineering with the University of Macau, where he directs the Smart and Micro/Nano Systems Laboratory. He was a Visiting Scholar with the Swiss Federal Institute of Technology, Zurich, Switzerland, the National University of Singapore, Singapore, RMIT University, Melbourne, VIC, Australia, and the University of California at Los Angeles, Los Angeles, CA, USA. His current research interests include microsystem/nanosystem, micromechatronics/nanomechatronics, robotics and automation, smart materials and structures, and intelligent control. Dr. Xu is a Fellow of the Institute of Electrical and Electronics Engineers (IEEE) and American Society of Mechanical Engineers (ASME). He is currently an Associate Editor of IEEE Transactions on Robotics and International Journal of Advanced Robotic Systems, and Editorial Board Member of Chinese Journal of Mechanical Engineering. He was a Technical Editor of IEEE/ASME Transactions on Mechatronics and an Associate Editor of IEEE Transactions on Automation Science and Engineering and IEEE Robotics and Automation Letters.

Personal Homepage: https://www.fst.um.edu.mo/personal/qsxu/