Bending the rules: Magnetically-actuated surgical continuum manipulators

Abstract

Continuum manipulators have revolutionized the field of minimally invasive surgery (MIS) in the past few decades. Major advances in fiber optics, imaging technologies, teleoperation, and haptics have accelerated the development of robot-assisted surgeries. The continuum manipulators used in robot-assisted surgery are equipped with laparoscopic tools as end effectors to augment the hand movements of the surgeon with precision. With robot assistance, surgeons can perform complex procedures inside the human body with high dexterity. However, the continuum robotics research community has challenged the lack of intuitive and effective operation of the surgical tools. Much uncertainty still exists about the tool-tissue interactions which have associated risks of tissue damage caused by unreliable control and articulation of the tool. This problem is further exacerbated by the limited visualization resolution of internal organs of the human body for safe operation. There is a pressing need to develop continuum manipulators with improved maneuverability and control to reach difficult-to-access surgical sites accurately.The aforementioned challenges of MIS play a critical role in the design and development of surgical continuum manipulators. The concept of compliant mechanisms (CMs) has been central to the design of various surgical devices. CMs are flexible mechanisms that use elastic deformation to transfer or transform force, motion, or energy. Devices made of CMs are generally monolithic in nature which leads to simplified fabrication, no wear, no friction, therefore, beneficial in high precision applications. CMs and their sub-components are increasingly used to enhance the range of motion and articulation of surgical continuum manipulators. Recently, magnetic actuation has emerged as a powerful means to execute several surgical functions such as instrument positioning, navigation, grasping, resection, and retraction. Magnetic actuation coupled with CMs has considerable impact in the design of miniaturized manipulators that eliminates the need for any cables tethered for control. Furthermore, accurate modeling of the continuum manipulators and integration of embedded sensing have been effective in the localization of manipulators. Real-time three-dimensional (3D) shape sensing of manipulators in tandem with medical imaging modalities aids in iii closed-loop control strategy to trace different trajectories with the tip of the manipulator is demonstrated. Clinical feasibility of the manipulator as a steerable catheter is shown in phantoms of a bifurcating artery and a heart with the guidance of a miniature camera.Part II explores the concept of variable stiffness mechanisms for surgical applications focusing on grasping and shape locking. Chapter 5 presents a magnetically-actuated variable stiffness robot (VSR). It is made of a soft magnetic elastomer with a sliding nitinol backbone. The synchronised retraction of the backbone with magnetic actuation leads to high deformation coiling action of the VSR. The grasping of ...