Navigation of Magnetic Microrobotic Swarms With Maintained Structural Integrity in Fluidic Flow

Micro/nanorobots offer great promise in the next generation of biomedical applications. One of the significant challenges to apply micro/nanorobots in the circulatory system is that fluidic flow impacts their motion and swarm behaviors. Herein, we propose an actuation strategy to navigate paramagnetic nanoparticle swarms and maintain their integrity in fluidic flow. The generation, locomotion, and integrity of the swarms in fluidic flow were analyzed and validated in experiments. Our results show that the nanoparticles should be pregathered as a swarm before releasing them into fluidic flow to maintain an integrated shape. The swarm integrity is dependent on the flow rate, and the strength and pitch angle of the applied oscillating magnetic field. Based on the findings, the actuation strategy for swarm navigation in fluidic flow was established. The strength and pitch angle of the magnetic field were tuned to maintain swarm integrity while the field pitch angle was tuned to change swarm velocity. Using the proposed strategy, downstream and upstream navigation of the swarm were realized in a blood flow with a rate of 2 mm/s. It was also demonstrated that the swarm can be navigated into a tube for retraction. The downstream delivery rate and upstream retraction rate of the nanoparticles were 99.4% and 75.7%, respectively.