Research On Medical Multimer Magnetic Microrobot And Motion Behavior Regulation

The last decades have witnessed great advances in magnetically driven micro/nanorobots,including innovative fabrication methods,reconfigurable and programmable navigation techniques,and various application.However,in the face of biomedical applications,the uneven groove morphology(～30 μm)of biological tissue surface in moving environment will greatly reduce the directional motion efficiency of the magnetic microrobot(<10 μm),and increase the difficulty of movement and control of microrobot.Moreover,the blood flow with high viscosity(～15 m Pa·s)and high velocity(～20000 μm/s)in the blood vessel will seriously hinder the movement of the magnetic microrobot and even wash it away.To address the two challeneges,this dissertation first preaents a solution based on magnetic control self-assembly multimer microrobot for moving on uneven tissue surface.Symmetric dimer,asymmetric dimer,trimer microrobots are constructed,and their motion control and obstacle crossing under the complex environment of uneven biological tissue surface are explored.Furthermore,the surface claw-engaged structure of the spherical microrobot is constructed to improve the motion performance against blood flow,and the feasibility of the scheme was verified by animal experiments in vivo.The basic theory of driving mechanism and motion characteristics of multimer microrobot is studied.The multimer microrobots with symmetric dimer,asymmetric dimer and trimer configurations are established based on magnetic self-assembly of spherical microrobots.The molecular dynamics models of the interaction between the multimer microrobot and the liquid medium environment is developed.Combined with experiments,the interaction driving mechanism of the dimer microrobot and the liquid medium,movement velocity and posture characteristics are analyzed.The dual-asynchronization dominated by the configuration-averaged magnetic dipole moment and dynamic stability dependent on magnetic potential energy are revealed.A method for the selective reconfiguration of configuration of the trimer microrobot dominated by the magnetic frequency is established.These results provide theoretical guidance for dynamic self-assembly,multi-configuration customization,and multimodal motion regulation of multimer microrobot.The obstacle crossing of multimer microrobot on biological tissue surfaces is studied.To overcome the structural barriers of multiple folds and irregularities on the biological tissue surface,a method based on the regulation of external magnetic field to realize the controllable movement of the multimer microrobot on the uneven biological tissue surface is proposed.The mechanisms of multimodal locomotion of tumbling,rolling and swing dependent on magnetic frequency are analyzed.A control strategy for rolling along the long-axis and rolling along the short-axis of the trimer microrobot co-dominated by the configuration distribution and the type of magnetic field is formulated.The experimental results of biological tissue obstacle crossing illustrate that the efficient adaptive movement and obstacle crossing on the surface of complex tissue topography are achieved by modulating the multimodal locomotion of the multimer microrobot.The research on controllable motion of claw-engaged microrobots in blood vessel is carried out.Aiming at the high-viscosity and high-speed blood flow environment in the blood circulatory system,a method to realize the controllable intravascular motion of the magnetic microrobot through the surface claw-engaged microstructure is proposed.A biocompatible and degradable magnetic claw-engaged microrobot is fabricated through self-growth technology,layer-by-layer self-assembly technology and cell membrane camouflage technology.The magnetization,adhesion and magnetic propulsion characteristics of claw-engaged microrobot are analyzed.The magnetic propulsion against blood flow with rate of up to 2.1 cm/s and active retention on blood vessel upon flow rate of 3.2 cm/s of claw-engaged microrobot and its multimers are achieved in experiments.Moreover,in vivo experiments of claw-engaged microrobots in jugular vein of rabbit is carried.Tha IVOCT is utilized to to build a driving and navigating system of microrobot in vivo.The magnetic propelled upstream and long-term active retention beyond 24 hours of claw-engaged microrobots are achieved in jugular vein of rabbit.In summary,aiming at the challenges of the uneven groove morphologyof biological tissue surface and the blood flow with high viscosity and high velocity in the blood vessel,this dissertation studys the self-assembled multimer configuration and self-growing surface claw-engaged structure of magnetic microrobots.The regulation of multimodal motion of the multimer microrobots is used to achieve efficient motion on uneven biological tissue surface.A magnetic microrobot with claw-engaged structure is fabricated by bionic design,to realize efficient upstream and active long-term retention in living biological veins.The related research results provide a new method for targeted drug delivery in vivo of magnetically driven micro/nanorobots,which has important application prospects and research value.