Automated Manipulation of Microswarms Without Real-Time Image Feedback Using Magnetic Tweezers

Microswarms assembled by microparticles have shown promising prospects in targeted delivery. However, the automated manipulation of microswarms remains a considerable challenge due to the limitations of existing in vivo imaging technology. In this article, we design a magnetic tweezer system with a large workspace of 100 mm × 100 mm × 30 mm, which can assemble, transport, and disassemble microswarms efficiently. The magnetic tweezers generate rotating magnetic fields in the workspace, enabling magnetized microparticles to roll toward a specific point along spiral trajectories. The assembly process and mechanism of microswarms are analyzed. The developed system can assemble low-density magnetic microparticles to form a stable and compact microswarm at a predetermined position. Actuation of the magnetic tweezers allows precise navigation of the swarm without relying on real-time image feedback. The experimental results show that the flexible microswarm can achieve satisfactory motion performance and transmission efficiency. The microswarm can successfully move on a slope with an inclination angle of $40^\circ $ and navigate analog channels. The overall delivery efficiency can reach 92%.