Magnetic Microrobots

Definitional Boundaries & Taxonomy

Magnetic microrobots are untethered, sub-millimeter-scale electromechanical or soft-matter systems designed to operate in complex, fluidic, or viscoelastic environments (predominantly in vivo) by harvesting power and control signals from external magnetic fields. Operating within a dimensional scale ranging from $1\mu m$ to $1000\mu m$, these systems exist in a physical regime where volumetric forces (inertia, gravity) are entirely negligible compared to surface forces (viscous drag, surface tension, electrostatic interactions). This defines the low Reynolds number ($Re\ll 1$) hydrodynamic regime. The taxonomy of magnetic microrobots is heavily dictated by their locomotion strategies and morphological architectures: Helical Swimmers mimic bacterial flagella (e.g., E. coli) utilizing rotational-to-translational coupling; Flexible Flagellated Swimmers rely on propagated bending waves along an elastic tail; Surface Rollers/Walkers utilize magnetic gradients or rotating fields to tumble or walk along endothelial boundaries; and Soft Bio-inspired Crawlers execute peristaltic or inchworm-like deformations using heterogeneous magnetic anisotropy embedded within soft elastomeric matrices.