Manipulation and navigation of micro
and nanoswimmers in different
fluid environments can be achieved by chemicals, external fields,
or even motile cells. Many researchers have selected magnetic fields
as the active external actuation source based on the advantageous
features of this actuation strategy such as remote and spatiotemporal
control, fuel-free, high degree of reconfigurability, programmability,
recyclability, and versatility. This review introduces fundamental
concepts and advantages of magnetic micro/nanorobots (termed here
as âMagRobotsâ) as well as basic knowledge of magnetic
fields and magnetic materials, setups for magnetic manipulation, magnetic
field configurations, and symmetry-breaking strategies for effective
movement. These concepts are discussed to describe the interactions
between micro/nanorobots and magnetic fields. Actuation mechanisms
of flagella-inspired MagRobots (i.e., corkscrew-like motion and traveling-wave
locomotion/ciliary stroke motion) and surface walkers (i.e., surface-assisted
motion), applications of magnetic fields in other propulsion approaches,
and magnetic stimulation of micro/nanorobots beyond motion are provided
followed by fabrication techniques for (quasi-)spherical, helical,
flexible, wire-like, and biohybrid MagRobots. Applications of MagRobots
in targeted drug/gene delivery, cell manipulation, minimally invasive
surgery, biopsy, biofilm disruption/eradication, imaging-guided delivery/therapy/surgery,
pollution removal for environmental remediation, and (bio)sensing
are also reviewed. Finally, current challenges and future perspectives
for the development of magnetically powered miniaturized motors are
discussed.