Strong magnetic actuation system with enhanced field articulation through stacks of individually addressed coils

Abstract

Abstract Miniaturization of medical tools promises to revolutionize surgery by reducing tissue trauma and accelerating recovery. Magnetic untethered devices, with their ability to access hard-to-reach areas without physical connections, emerge as potential candidates for such miniaturization. Despite the benefits, these miniature devices face challenges regarding force and torque outputs, restricting their ability to perform tasks requiring mechanical interactions such as tissue penetration and manipulation. To overcome magnetic actuation system-based force and torque limitations, this study proposes Variable Outer Radius Individually Addressable Coil Stacks (VORIACS), a novel magnetic actuation system optimized for high force output generation to magnetic devices within its workspace. The VORIACS marks significant improvements and breakthroughs in magnetic actuation within decimeter-scale workspace. The VORIACS is comprised of 12 coils that are optimized for 2D magnetic field generation under maximized power consumption of up to 12 kW. We implement six two-channel motor controllers, powered by six separate power supplies. Each of the twelve coils in the system is operated on its own motor-controller channel. This arrangement allows the system to exceed the magnetic forces and torques possible for single-coil versions of the same geometry. This study elaborates on optimizing, manufacturing, integrating, and demonstrating this system. Comparative analysis reveals that while a suboptimal, single-coil version of this system generates 0.31 N force (710 mT/m magnetic gradient magnitude), the VORIACS produces 1.673 N force (3834 mT/m magnetic gradient magnitude) on the same magnetic object placed 5 cm away from the coils. Moreover, the strong penetration force generated by VORIACS enables needle penetration to a mock gel that has the rigidity of liver tissue. In addition, we demonstrate the advantage of stacked coils with variable radii for magnetic field manipulability while maintaining the optimized force delivery property of the system, which improves control and could facilitate multi-tool manipulation. By enabling a fivefold increase in magnetic pulling force compared to its single-coil counterpart, VORICAS raises the potential penetration capabilities of untethered magnetic robotics in surgical procedures.