Multi-Mode Motion Control of Reconfigurable Vortex-Shaped Microrobot Swarms for Targeted Tumor Therapy

Micro-nano robots with low invasiveness and high drug utilization are considered a promising approach for tumor therapy. However, individual micro-nano robots are limited in terms of motility, drug-carrying capacity, and environmental adaptability. This study proposes a clustering control strategy for magnetic nanoparticles that enables individual loose particles to be organized into vortex-like swarms and chain-like ones with rapid transitions across them. The vortex-like swarm of microrobots can be precisely navigated through a visual feedback mechanism. The positions error of their movements can be controlled under 22 $\mu {\mathrm{m}}$. We constructed a tumor microenvironment. The vortex-swarm robots can easily adapt to undulating terrains, overcome the obstruction of flowing blood and a massive number of blood cells, and propel itself at an overall speed of faster than 170 $\mu {\mathrm{m}}$/s. In addition, the vortex-swarm robots can navigate through magnetic fields to reach the tumor location in an arbitrary area and kill cancer cells precisely with the photothermal effect of magnetic nanoparticles, resulting in a cancer cell viability rate of 1.65%. The cluster-based precision control of micro-nano robots will deliver significant advantages for targeted tumor therapy in the future.