Abstract
Soft microrobots, compared with their rigid counterparts, offer superior adaptability in dynamic and confined biological environments. Here, magnetically-guided liquid metal microrobots composed of gallium-indium alloys embedded with Fe nanoparticles are introduced. The unique combination of magnetic maneuverability, high surface tension, intrinsic radiopacity, and deformability allows liquid metal-based microbots to overcome limitations of both hard microrobots and fragile droplet-based systems. Under magnetic actuation, liquid metal-based magnetic microrobots exhibit controllable rolling and upstream locomotion resembling neutrophil-like navigation, enabling precise maneuvering even against physiological flow. Bridging in vitro with in vivo experiments, quail egg chorioallantoic membrane models are used to demonstrate guided transport of these microrobots through blood vessels, accumulation at tumor xenografts, and migration within subcutaneous tissues. Moreover, their strong X-ray visibility enables real-time fluoroscopic tracking, validated in porcine heart vasculature. Importantly, liquid metal-based magnetic microbots can cross endothelial barriers in a vascular flow-on-a-chip platform, while maintaining endothelial biocompatibility. By integrating deformability, magnetic steerability, and imaging visibility, liquid metal-based microrobots establish a powerful platform for minimally invasive transvascular navigation. This work highlights the potential of liquid metal-based magnetic microrobots for targeted drug delivery, image-guided therapy, and intelligent biomedical interventions.