磁场驱动柔性微纳机器人研究进展

 磁场驱动微纳机器人无需化学燃料，因而可以在水、血浆、组织液等多种液体环境中使用。它可以在生物体内进行无损伤远程调控，并易于进行运动控制，这些特点使得它在医疗领域具有广泛的应用前景。微纳机器人尺寸极小，处于低雷诺数环境中，需要克服高黏性力实现运动。磁场驱动微纳机器人有表面型、螺旋型和柔性驱动型3种。柔性的磁场驱动机器人通过外界磁场力产生周期性变形，在低雷诺数环境中实现推进，与微生物的推进方式类似，具有推进效率高、对磁场强度要求低的优点。本文综述了磁场驱动柔性微纳机器人的制备、驱动方式、运动性能和运动控制性能研究进展。

Review on magnetic powered flexible micro-/nanomotor

Magnetic powered micro-/nanomotors can be used in a variety of fluids, such as water, blood plasma and tissue fluid, because they are not driven by fuels. It can be remotely actuated in living organisms by an external magnetic field, noninvasively. The motion control of magnetic micro-/nanomotors can be easily achieved by modulating the external magnetic field generated by electromagnet. With these inherent advantages, magnetic micro-/nanomotors find a wide range of potential applications for medical treatments such as the targeted drug delivery and the cell manipulation. Swimming devices in a low Reynolds number environment must overcome the high viscosity force to achieve propulsion. The Scallop theorem requires that the flexible micro-/nanomotors must deform in a way which is not invariant in a time-reversal process. By these principles, three types of magnetic powered micro-/nanomotors were developed, which are the surface walkers, the helical magnetic propellers and the flexible magnetic propellers. Natural microorganisms achieve propulsion with flexible flagella or rigid helical flagella to break the time-reversal process. Inspired by swimming of microorganisms, the magnetic powered flexible micro-/nanomotors achieve motion in a low Reynolds number environment by a cyclic deformation powered by an external magnetic field. This type of flexible micro-/nanomotors have a high propulsion efficiency thus require a low magnetic field intensity. Four topics concerning this type of micro-/nanomotor are elaborated in this paper, namely, the fabrication, the mode of locomotion, the propulsion performance and the motion control. At last the problems that remain to be solved and the development tendency of magnetic powered flexible micro-/nanomotors are discussed.