Physiologically Adaptive Soft Millirobot for Atraumatic Endovascular Therapy

Atraumatic and localized drug delivery to the vascular endothelium remains a critical unmet need in interventional medicine, with major implications for arterial and venous disease management. Here, we present EndoBot, a soft, untethered millirobot designed to enable physiologically adaptive endoluminal interaction for atraumatic navigation and localized drug delivery under blood flow. EndoBot employs mechanically adaptive surface crawling that allows it to traverse non-uniform and curved vasculature while maintaining low radial contact pressures (<1 kPa), well below endothelial injury thresholds. We demonstrate stable, surface-conformal locomotion under arterial and venous flow conditions in phantom vessels, ex vivo human umbilical veins under normothermic perfusion, and an in vivo rat inferior vena cava model, without mechanical vessel injury despite geometric irregularities and periodic body motion. EndoBot is compatible with standard vascular sheaths for wireless deployment and retrieval and is controlled under clinical fluoroscopic guidance using a human-scale magnetic manipulation platform. Blood compatibility testing confirms safety, with minimal hemolysis and no increased coagulation tendency during actuation. For drug delivery, EndoBot employs an endoluminal painting strategy that transfers a biodegradable, flow-resistant drug depot directly onto the vessel lumen, overcoming washout under physiologic flow. By enabling localized endothelial drug delivery without compromising vessel wall integrity, EndoBot establishes a translationally viable platform that pave the way for preventive and maintenance-oriented endovascular therapies.