What if soft robots could move through narrow internal pathways, deliver therapies, assist diagnosis, and support minimally invasive procedures without carrying onboard motors or batteries? Conventional medical instruments have transformed diagnosis and intervention, but they still face important limitations when procedures require access to narrow, tortuous, or delicate internal environments. Small-scale magnetic soft robots, or SMSRs, offer a possible route beyond these limits. By using external magnetic fields for remote actuation, these robots can avoid onboard power sources and internal actuators while maintaining soft, compliant interaction with biological tissues. Their potential applications include endoscopic imaging, biopsy and sampling, physiological monitoring, minimally invasive surgery, endovascular intervention, drug delivery, magnetic skin, tissue repair, and biomimetic muscle systems.
The review organizes in vivo SMSRs into two representative categories: untethered and tethered robots. Untethered robots operate without physical connections and can move through the body under magnetic control by swimming, crawling, rolling, undulating, or jumping. This makes them attractive for patient-friendly and less invasive tasks, especially in extended luminal organs such as the gastrointestinal tract. Tethered robots, by contrast, remain connected through flexible catheters, guidewires, or continuum bodies. Although this physical connection limits complete freedom of motion, it can improve stability, positional accuracy, signal transmission, and tool delivery, making tethered systems more suitable for delicate targeted interventions in regions such as the cardiovascular, neurovascular, and head–neck areas.
A central feature of the article is its five-stage translational framework. The first stage, basic performance testing, evaluates magnetic response, locomotion, deformation, structural stability, and preliminary functional integration. The second stage, artificial model testing, uses anatomical phantoms such as vascular networks or gastrointestinal models to assess navigation and task execution in body-like structures. The third stage, ex vivo organ testing, examines robot performance in real biological tissues. The fourth stage, animal in vivo testing, evaluates operation under dynamic physiological conditions. The fifth stage, clinical testing, focuses on feasibility, safety, efficacy, workflow compatibility, and patient tolerance.
The review also emphasizes that laboratory success does not automatically translate into clinical readiness. Both untethered and tethered SMSRs face shared barriers, including insufficient biocompatibility validation, difficulty integrating multiple diagnostic and therapeutic functions, limited imaging and localization accuracy, incomplete safety evidence, and the lack of standardized testing and regulatory pathways. Artificial models may not fully reproduce real tissue friction, elasticity, mucus, blood flow, or anatomical variability, while ex vivo organs lack living physiological dynamics. Even at the clinical stage, current studies often involve limited sample sizes, narrow indications, and incomplete integration with routine medical workflows.
Looking forward, the authors suggest that untethered and tethered SMSRs should not be viewed as competing technologies, but as complementary tools within future clinical workflows. Untethered systems may support broad exploration, noninvasive diagnosis, large-area lesion detection, and localized delivery, while tethered systems may provide higher precision for targeted intervention, real-time feedback, and delicate surgical manipulation. To move the field closer to clinical use, future studies will need standardized stage-by-stage evaluation, stronger biocompatibility and biosafety evidence, improved actuation–imaging coupling, closed-loop magnetic control, artificial intelligence-assisted navigation, and larger-scale animal studies and clinical validation. In the longer term, hybrid tethered–untethered systems could combine free locomotion with stable access and tool delivery, helping transform small-scale magnetic soft robots from promising laboratory prototypes into reliable instruments for minimally invasive medicine.
SmartBot
Small-Scale Magnetic Soft Robots for Medical Applications: From Laboratory to Clinical Use
20-May-2026
The authors declare no conflicts of interest.