Promising advances in physically propelled micro/nanoscale robots

Micro/nanoscale robots (MNRs) have attracted significant interest in various fields because of their flexible design, physically controlled maneuvering, and barrier targeting. The execution of specific functions using MNRs relies on precise propulsion methods. Among the diverse propulsion techniques, physical propulsion is widely used owing to its noninvasive, safe, and convenient attributes. This review provides an analysis of the propulsion mechanisms in the magnetic, electric, thermal, and ultrasound fields and presents a comprehensive summary of the structures, movements, and applications of various MNRs while also examining their advantages and shortcomings associated with various physical propulsion methods. Finally, challenges and perspectives associated with the future development of MNRs are presented. The content of this review can serve as a multidisciplinary science reference for physicists, bioengineers, clinicians, roboticists, and chemists involved in pharmaceutical design and clinical therapy research.