Hard‐Magnetic Soft Millirobots in Underactuated Systems

Hard‐magnetic soft millirobots combine flexible polymer matrices with magnetic particles to achieve precise, remotely controlled deformation and locomotion. Their small size and mechanical compliance enable safe navigation through complex biological environments, offering transformative potential for biomedical applications. This review systematically examines key developments in their design, modeling, and control. We analyze magnetic actuation principles and the underactuation challenges posed by global field control of continuum structures. Various robot architectures, including continuum, sheet‐like, and bioinspired designs, are compared for their motion capabilities. The discussion covers modeling techniques ranging from analytical methods to multiphysics simulations, which have been used to study coupled magnetomechanical behavior. Control strategies ranging from open‐loop programming to adaptive learning‐based approaches are evaluated. The review highlights biomedical applications in targeted therapy, minimally invasive diagnosis, and precision interventions. Finally, we identify critical challenges in materials development, real‐time control, and clinical translation, providing insights for future research directions in this emerging field.