Magnetically actuated robots have proven effective in several applications, specifically in medicine. However, generating high actuating fields with a high degree of manipulability is still a challenge, especially when the application needs a large workspace to suitably cover a patient. The presented work discusses a novel approach for the control of magnetic field and field gradients using two robotically actuated permanent magnets. In this case, permanent magnets—relative to coil-based systems—have the advantage of larger field density without energy consumption. We demonstrate that collaborative manipulation of the two permanent magnets can introduce up to three additional Degrees of Freedom (DOFs) when compared to single permanent magnet approaches (five DOFs). We characterized the dual-arm system through the measurement of the fields and gradients and show accurate open-loop control with a 13.5% mean error. We then demonstrate how the magnetic DOFs can be employed in magnetomechanical manipulation, by controlling and measuring the wrench on two orthogonal magnets within the workspace, observing a maximum crosstalk of 6.1% and a mean error of 11.1%.

Simulation represents a key aspect in the development of robot systems. The ability to simulate behavior of real-world robots provides an environment where robot designs can be developed and control systems optimized. Due to the use of external magnetic fields for actuation, magnetic soft robots can be wirelessly controlled and are easily miniaturized. However, the relationship between magnetic soft materials and external sources of magnetic fields present significant complexities in modelling due to the relationship between material elasticity and magnetic wrench (forces and torques). In this work, we present a simulation framework for magnetic soft robots using the Material Point Method (MPM) which integrates hyper-elastic material models with the magnetic wrench induced under external fields. Compared to existing Finite Element Methods (FEM), the presented MPM based framework inherently models self-collision between areas of the model and can capture the effect of forces in non-homogeneous magnetic fields. We demonstrate the ability of the MPM framework to model the influence of magnetic wrench on magnetic soft robots, capture dynamic behavior of robots under time-varying magnetic fields, and provide an accurate representation of deformation when colliding with obstacles. We show the versatility of MPM framework by comparing simulations to a range of real-world magnetic soft robot designs previously presented in the literature.

Independent robotic manipulation of two large permanent magnets, in the form of the dual External Permanent Magnet (dEPM) system has demonstrated the possibility for enhanced magnetic control by allowing for actuation up to eight magnetic degrees of freedom (DOFs) at clinically relevant scales. This precise off-board control has facilitated the use of magnetic agents as medical devices, including catheter-like soft continuum robots (SCRs). The use of multiple robotically actuated permanent magnets poses the risk of collision between the robotic arms, the environment, and the patient. Furthermore, unconstrained transitions between actuation inputs can lead to undesired spikes in magnetic fields potentially resulting in unsafe manipulator deformation. This paper presents a hybrid approach to trajectory planning for the dEPM platform. This is performed by splitting the planning problem in two: first finding a collision-free physical path for the two robotically actuated permanent magnets before combining this with a path in magnetic space , which permits for a smooth change in magnetic fields and gradients. This algorithm was characterized by actuating each of the eight magnetic DOFs sequentially, eliminating any potential collisions and reducing the maximum undesired actuation value by 203.7 mT for fields and by 418.7 mT/m for gradients. The effect of this planned magnetic field actuation on a SCR was then examined through two case studies. First, a tip-driven SCR was moved to set points within a confined area. Actuation using the proposed planner reduced movement outside the restricted area by an average of 41.3%. Lastly, the use of the proposed magnetic planner was shown to be essential in navigating a multi-segment magnetic SCR to the site of an aneurysm within a silicone brain phantom.

Drawing inspiration from natural growth and movement strategies, vine robots possess exceptional passive shape-forming abilities, enabling them to deform around obstacles. However, an intrinsic lack of active steering limits their capacity to control their growth trajectory. This letter considers the external manipulation of such robots through the utilization of magnetically active materials embedded within the vine robot's skin. This results in a completely flexible, steerable, growing structure that can be actuated via the application of external magnetic fields and field gradients. We explore the principles of magnetically-guided vine robots and provide empirical evidence highlighting the efficacy of our proposed magnetic steering methodology. Due to the inverted internal structure, careful design of the magnetization direction of the robot has to be considered. We propose an orthogonal magnetization strategy that successfully preserves a net positive magnetization. We focus on a vine robot of 8 mm in diameter, constructed from a polyethylene substrate coated with a silicone layer embedded with magnetic micro-particles. We demonstrate the ability of our robots to navigate complex environments and steer around large obstacles in a shear free manner via the simultaneous control of both the magnetic field and the growing pressure. Finally, we demonstrate our robot by performing the selective navigation of multiple bifurcations within a bronchial tree phantom.

There is a growing need for precise, minimally invasive biopsy techniques that reduce patient discomfort, improve sampling accuracy in hard‐to‐reach areas, and minimize tissue damage. Vine robots, a type of continuum robot, offer a promising solution with their unique ability to evert, allowing them to navigate complex environments while reducing friction. This article presents a novel vine robot design powered by magnetic fluid. The fluid drives both vine growth through pressurization and enables precise steering and manipulation using external magnetic fields. Unlike previous designs, the robot's high magnetic volume ensures precise control even under pressure, while maintaining a fully soft structure. This allows for controlled needle movements during biopsies. Additionally, the robot achieves passive stabilization by pressing against surrounding walls. This stabilization, combined with magnetic forces, can exert up to 1.26 N of insertion force at the tip, enabling effective tissue penetration. Experiments are conducted with a 5 mm diameter, 145 mm long magnetic fluid‐driven vine robot, demonstrating movement in free space, through narrow constrictions, and within phantoms modeled after human bronchial anatomy. These results pave the way for the robot's potential application in minimally invasive surgeries, particularly in difficult‐to‐access areas of the body.

This article explores the concept of external magnetic control for vine robots to enable their high curvature steering and navigation for use in endoluminal applications. Vine robots, inspired by natural growth and locomotion strategies, present unique shape adaptation capabilities that allow passive deformation around obstacles. However, without additional steering mechanisms, they lack the ability to actively select the desired direction of growth. The principles of magnetically steered growing robots are discussed, and experimental results showcase the effectiveness of the proposed magnetic actuation approach. We present a 25-mm-diameter vine robot with an integrated magnetic tip capsule, including 6 degrees of freedom (DOF) localization system and camera, and demonstrate a minimum bending radius of 3.85 cm with an internal pressure of 30 kPa. Furthermore, we evaluate the robot’s ability to form tight curvature through complex navigation tasks, with magnetic actuation allowing for extended free-space navigation without buckling. The suspension of the magnetic tip was also validated using the 6 DOF localization system to ensure that the shear-free nature of vine robots was preserved. Additionally, by exploiting the magnetic wrench at the tip, we showcase preliminary results of vine retraction. The findings contribute to the development of controllable vine robots for endoluminal applications, providing high tip force and shear-free navigation.