Hydrogel-Based Micro/Nanorobots for Advanced Biomedical Applications

Micro/nanorobotics is emerging as a promising biomedical technology because of its precision, minimal invasiveness, multifunctionality, and potential to mitigate systemic adverse effects. At these ultraminiaturized scales, unique physical constraints necessitate design principles and actuation strategies distinct from those of conventional robotic systems, making material choice, structural design, propulsion mechanisms, and fabrication methods central to overall performance. In this review, we examine recent trends in micro/nanorobot development, with particular emphasis on the advantages of employing hydrogels and the current technical limitations associated with their use. Magnetic, chemical, acoustic, optical, and biohybrid propulsion strategies are comparatively analyzed, together with the material requirements and biological compatibility associated with each approach. Representative applications in drug delivery, tissue regeneration, and cancer therapy are further discussed to highlight the broad medical potential of these systems. Finally, remaining challenges related to material limitations, actuation efficiency, biocompatibility, and manufacturing scalability are identified, and future directions toward clinical translation and practical deployment are outlined. Overall, this review provides an integrated perspective on how hydrogel properties, actuation physics, fabrication strategies, and translational considerations collectively shape the development of more adaptive, biocompatible, and clinically relevant microrobotic systems.