Magnetic Soft Helical Manipulators with Local Dipole Interactions for Flexibility and Forces.

Magnetic continuum manipulators (MCMs) are a class of continuum robots that can be actuated without direct contact by an external magnetic field. MCMs operating in confined workspaces, such as those targeting medical applications, require flexible magnetic structures that contain combinations of magnetic components and polymers to navigate long and tortuous paths. In cylindrical MCM designs, a significant trade-off exists between magnetic moment and bending flexibility as the ratio between length and diameter decreases. In this study, we propose a new MCM design framework that enables increasing diameter without compromising on flexibility and magnetic moment. Magnetic soft composite helices constitute bending regions of the MCM and are separated by permanent ring magnets. Local dipole interactions between the permanent magnets can reduce bending stiffness, depending on their size and spacing. For the particular segment geometry presented herein, the local dipole interactions result in a 31% increase in angular deflection of composite helices inside an external magnetic field, compared to helices without local interactions. In addition, we demonstrate fabrication, maneuverability, and example applications of a multisegment MCM in a phantom of the abdominal aorta, such as passing contrast dye and guidewires.