A ciliated intravascular soft millirobot for multimodal in-flow collective manipulation.

The laminar nature of blood flow and the resulting boundary layer pose substantial challenges for transverse mass transport in blood vessels, limiting intravascular biomedical applications such as targeted delivery, thrombolysis and biomarker enrichment. Herein, we develop a ciliated intravascular millirobot, CiliaVine, for active manipulation of particle and cell collectives through flow regulation. Actuated by tailored magnetic fields, soft cilia on the robot oscillate in different modes, generating desired flow patterns for flow regulation. CiliaVine enhances the transverse transport that is otherwise suppressed under laminar flow, driving circulating collectives from the vessel center toward the vessel wall for drug penetration, or reversing transport for thrombus residue clearance. Flow regulation is investigated in a vascular model using fluorescent tracer particles. Enhanced targeted drug delivery and accelerated thrombolysis enabled by the robot are validated. Circulating tumor cell (CTC) enrichment is evaluated using cancer patient blood and in tumor-bearing rabbits, revealing its effectiveness in physiological environments and its potential for intravascular rare-cell enrichment.