Untethered & Stiffness-Tunable Ferromagnetic Liquid Robots for Cleaning Thrombus in Complex Blood Vessels

Thrombosis is a significant threat to human health. However, the existing clinical treatment methods have limitations. Magnetic soft matter is used in the biomedical field for years, and ferromagnetic liquids exhibit tunable stiffness and on-demand movement advantages under magnetic fields. In this study, a ferromagnetic liquid robot (FMLR) is developed and applied it to thrombus removal in complex blood vessels. The FMLR consisted of Fe₃O₄ magnetic nanoparticles and dimethyl silicone oil. The FMLR can pass through a narrow complex maze through shape deformation by tailoring the intensity and direction of the external magnetic field. Finite element simulation analysis is used to validate the mechanism of controllable FMLR movements. Importantly, the storage modulus of FMLR can be tuned from 0.1 to 2018 Pa by varying the external magnetic intensity, ensuring its effectiveness in removing rigid and stubborn thrombi present on the vascular walls. Toward medical robotic applications, FMLR can be used in telerobotic neurointerventional. Experiments demonstrating the capability of FMLR to remove thrombi in the ear veins of rabbits are conducted. This study introduces an efficient approach for thrombus elimination, broadening the utilization of FMLRs within the realm of clinical medicine.