Design of Magnetic Continuum Robots and their Applications in Medicine
EMBARGOED UNTIL 2026-12-10
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2025
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Doctoral Thesis
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EMBARGOED UNTIL 2026-12-10
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Abstract
From its early creative applications in foreign body removal, to its modern use in imaging, magnetism has long played an important role in medicine. In recent decades, advances in magnetic field control and device fabrication have enabled the remote steering of medical instruments using external magnetic fields. This has opened new possibilities for minimally invasive interventions, particularly through the use of magnetically steered continuum robots.
These robots have emerged as a promising alternative to tendon driven systems, offering simpler and more compact designs, improved potential for miniaturization, and the possibility of wireless operation, teleoperation, and automation. However, they remain limited by low actuation torques, difficulties in standardization, and the inherent trade-off between flexibility, which enables efficient transmission of actuation torques, and stability, which prevents structural collapse. This thesis addresses these challenges through the development of a parametric design framework for magnetic continuum robots, demonstrated by the construction of a family of medical prototypes validated in vitro, ex vivo, and in vivo. In Part I, we analyze the fundamental design considerations of magnetic continuum robots and identify the limitations of existing architectures. From these insights, we introduce a parametric interlocking ball joint design that preserves magnetic volume, avoids kinking, and enhances structural robustness while maintaining continuous bending. The framework is implemented in an open-source CAD toolbox that accounts for manufacturing and tolerance constraints, enabling rapid and reproducible design. It allows users to generate functional prototypes without requiring prior expertise in mechanical design, providing a straight forward path from concept to fabrication.
In Part II, the framework is validated by building a series of medical devices of increasing complexity. A magnetically guided cardiac ablation catheter demonstrates rapid prototyping and functional ex vivo performance. A flexible endoscope for fetal surgery extends this to in vivo validation, integrating optical fibers, a working channel, and a camera system. The Lobsterscope further explores modularity by combining multiple nested and independently actuated backbones to perform multi-actuator operations through sequential shape-locking.
In Part III, building on these foundations, we present a transnasal endoscope that maintains the full functionality of traditional gastroscopes while reducing device size and invasiveness. The design integrates the ball joint architecture, a variable stiffness mechanism, and magnetic actuation into a compact system built for pre-clinical trials. Finally, the same system was used to perform a teleoperated gastroscopy over a distance of 9300 km between Zürich and Hong Kong with a communication delay below 300 ms, demonstrating that remote magnetic navigation enables safe and intuitive operation with minimal hardware modifications and highlighting its potential for geographically independent medical procedures.
Together, these results establish an architecture for the design of magnetic continuum robots, reducing reliance on trial-and-
error development. This work aims to simplify future progress in this field by providing a standardized experimental design and validation procedure, to advance the adoption of magnetic actuation in minimally invasive and remote medical procedures.
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ETH Zurich
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Subject
Parametric Design; Medical Endoscopes and Catheters; Magnetic Navigation
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03627 - Nelson, Bradley J. / Nelson, Bradley J.