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.
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