Shaping Magnetics in Surgical Robotics | A Dissertation on Continuum Robotics
Michiel Richter is a PhD student in the department Surgical Robotics. (Co)Promotors are prof.dr. S. Misra and dr. V. Kalpathy Venkiteswaran from the faculty Engineering Technology, University of Twente.
Medical continuum robots (MCRs), including flexible devices such as catheters, guidewires, and endoscopes, play an increasingly important role in minimally invasive procedures. While traditionally steered through manual manipulation and internal mechanical force transmission, magnetic actuation has emerged as a promising alternative. By applying external magnetic fields, forces and torques can be directly exerted on embedded magnets within these devices, enabling wireless control. This principle is particularly advantageous for steering long, slender instruments. Despite significant research advances, clinical adoption of magnetic actuation has remained limited, in part hindered by the complexity, cost, and physical footprint of the required infrastructure, as well as competition with simpler, more intuitive technologies.
This dissertation aims to enhance both the functionality and practicality of MCRs. It introduces magnetically responsive segments along the body of the robot to achieve deformation to intricate shapes. A quasi-static continuum mechanics model is developed to simulate deformations under magnetic fields, supporting closed-loop, multi-point orientation control and enabling shape-deforming behaviors akin to small-scale robotic arms. Smart materials with variable stiffness are integrated to create selectively shape-locking robots, allowing dynamic configuration and safe guidance of surgical tools, such as biopsy needles, within a three-dimensional workspace.
In addition to these control strategies, novel designs are proposed to harness internal magnetic interactions for improved flexibility and steerability of devices. A helical soft polymer structure is introduced to exploit localized magnetic forces, while MCRs with embedded magnetic sources and nonuniform magnetization profiles are engineered for task-specific functions like gripping or pulling. Finally, a new approach to magnetic localization is presented, reconstructing the 3D pose of a rotating magnetic dipole. This offers a compact, imaging-free alternative for in-body tracking.
Altogether, this work contributes to the development of more effective, versatile, and clinically viable magnetic continuum robots in future medical applications.
