Field-Superimposed Control Magnetically Driving Nanorobot Swarms with Hybrid Rotating and Gradient Fields

Abstract

Magnetically actuated micro/nanorobot swarms have exhibited considerable promise for targeted biomedical delivery and localized therapies, attributed to their advantages of remote manipulation and robust penetration through biological tissues. However, achieving the simultaneous enhancement of both collective structural stability and efficient propulsion under a single-mode magnetic field remains a critical challenge. This paper presents a rotational–gradient superimposed magnetic actuation strategy that enables precise superposition of a uniform rotating field and a directional gradient magnetic field, using a tri-axial electromagnetic coil system. This approach significantly enhances the motility of micro/nanorobots while preserving their collective stability. Experimental results reveal that a co-directional gradient magnetic field can increase cluster velocity by 1.5-2 times without compromising cluster stability, while a counter-directional gradient magnetic field enables effective deceleration or anchoring of the swarm. Also, this paper elucidates the impact of the gradient magnetic field on swarm stability. Moreover, this paper demonstrates the formation of the chain-like structure of micro/nanorobots, which possess axial movement capability under the superimposed gradient magnetic field. This work provides a systematic theoretical and experimental foundation for multi-field synergistic actuation of micro/nanorobot swarms, and paves new paths for their application in biomedical micromanipulation.