Magnetically Powered Micro- and Nanorobots: From Physical Principles to Medical Applications

Magnetically powered micro- and nanorobots have emerged as remotely controlled carriers and tools for minimally invasive medicine. Their performance is governed by magnetic torque and force, low-Reynolds-number hydrodynamics, interactions with biological interfaces and the ability to localize and control devices in real time. This review links these physical principles to helical swimmers, surface rollers, flexible swimmers, magnetic assemblies and biohybrid systems. We evaluate experimental evidence for drug delivery, tumour targeting, cell transport, thrombus-related interventions and localized manipulation, carefully distinguishing benchtop demonstrations from animal studies and clinically relevant integrated systems. We further examine the coupled challenges of magnetic-field generation, navigation in blood and mucus, imaging, dose delivery, materials safety, biodegradation and retrieval. A microrobot becomes medically useful only when propulsion, localization and therapeutic function remain effective within the same physiological environment. Consequently, the most plausible early applications combine a well-defined access route, a constrained anatomical target, compatible imaging and a clear advantage over existing delivery or interventional approaches. Finally, we outline benchmarks for reproducibility, biological fate and clinical translation. Twenty-three fully worked examples connect magnetic forces and torques to locomotion, actuator requirements, localization uncertainty, feedback control and drug exposure; their hypothetical inputs and simplifying assumptions are stated explicitly to support reproducible teaching and preliminary design. In this review, “micro- and nanorobots” is an inclusive small-scale robotics term: we report the complete device dimensions and explicitly identify micrometre- and millimetre-scale platforms, even when their magnetic or functional constituents are nanoscale.