基于磁场驱动的非手性微型机器人磁矩耦合及运动控制研究

   Motion control of magnetic microrobots in complex fluids promotes their use in targeted therapies. It is difficult for microrobots with a single form of motion to be controlled in complex environments, for example, over obstacles or through narrow channels. Microrobots with multimodal forms of locomotion can perform diverse micromanipulations in complex environments, which offer potential applications in the biomedical field.

  Microrobots were fabricated using photolithography, etching, and magnetron sputtering techniques, and their physicochemical properties were characterized. The roughness, hardness, thermal stability, and biocompatibility of the microrobots were analyzed, and the results showed that the prepared microrobots can meet the requirements for motion under magnetic field and have good biocompatibility.

   The locomotion of microrobots with different magnetic moment couplings was analyzed in non-Newtonian fluids. The motion control of microrobots with long-arm magnetization, long-axis magnetization, short-axis magnetization, and out-of-plane magnetization was investigated in a uniform rotating magnetic field in a 0.6% w/v methylcellulose solution. The results showed that if the coupled magnetic moment is parallel to one of the rotating axes, the microrobots have no net displacement in the uniform rotating magnetic field. Microrobots with long-arm magnetization can generate a net displacement but are insensitive to the clockwise and counterclockwise reversals of the magnetic field.

    A conical magnetic field control strategy was implemented to effectively control microrobots with different magnetic moment couplings. A conical magnetic field was generated by superimposing a uniform rotating magnetic field with a static magnetic field. Microrobots with no net propulsion were able to achieve swimming motion under the control of the conical magnetic field, and their direction could be effectively controlled. The conical magnetic field was successfully employed to control the motion of achiral microrobots in zebrafish embryo yolk while maintaining zebrafish survival during the microrobot motion process.

     Microrobots with different magnetic moment couplings exhibit multimodal motions, enabling diverse micromanipulations. Four types of microrobots with different magnetization directions exhibit two distinct locomotion modes under a uniform rotating magnetic field, with significant differences in speed and step-out frequency. This property is used to achieve microrobot locomotion in narrow channels and selective control in Y-shaped channels. Rolling microrobots generate multiple vortices around their bodies, enabling non-contact transportation of multiple polystyrene microspheres. The locomotion direction of long-arm magnetized microrobots in a uniform rotating magnetic field is guided by the orientation of the magnetized arm. This principle is utilized to achieve cooperative motion of two long-arm magnetized microrobots and three-level separation of microrobot swarms. These diverse microrobot manipulations hold immense potential for future applications in tasks such as vascular recanalization, tumor targeting, and transportation of fragile materials.
 

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