Assisted Magnetic Soft Continuum Robot Navigation via Rotating Magnetic Fields

Innovative robotic catheters that are soft, flexible, and controlled by magnets have the potential to revolutionize minimally invasive surgical procedures in critical areas such as the lungs, brain and pancreas, which currently pose significant safe access challenges using existing technology. These shape forming millimetre-scale magnetic soft continuum robots (MSCRs) can be designed to be highly dexterous in order to access regions of the anatomy otherwise deemed inaccessible. However, due to their soft and slender nature, MSCRs are prone to buckling under compressive loads during insertion. In this study we demonstrate buckling free insertion of high aspect ratio (80 mm long by 2 mm diameter) MSCRs into narrow, tortuous lumens enabled by coupling a specific lengthwise magnetic profile with exposure to a rotating magnetic field (RMF). We present design, finite element modelling (FEM) of the motion, fabrication and actuation of three different MSCRs. These robots are cast from NdFeB doped silicone polymer to obtain 2 mm and 3 mm diameter catheters. These are magnetized in a predefined profile such that when the catheters are placed in an RMF, a serpentine motion is generated. Experiments were conducted to quantify the behaviour of these soft catheters navigating through a soft phantom that mimicked narrow tortuous lumens such as the pancreas and bile ducts. Oscillating actuation increased the inserted depth reached by the MSCR in a tortuous channel and even enabled squeezing through a 1 mm diameter opening via shape morphing. The experiments showed that an RMF reduced the required insertion forces by almost 45% and increased the distance inserted in a fixed time frame by 3 times.