Bioinspired Soft Microrobots with Precise Magneto-Collective Control for Microvascular Thrombolysis.

New-era soft microrobots for biomedical applications need to mimic the essential structures and collective functions of creatures from nature. Biocompatible interfaces, intelligent functionalities, and precise locomotion control in a collective manner are the key parameters to design soft microrobots for the complex bio-environment. In this work, a biomimetic magnetic microrobot (BMM) inspired by magnetotactic bacteria (MTB) with speedy motion response and accurate positioning is developed for targeted thrombolysis. Similar to the magnetosome structure in MTB, the BMM is composed of aligned iron oxide nanoparticle (MNP) chains embedded in a non-swelling microgel shell. Linear chains in BMMs are achieved due to the interparticle dipolar interactions of MNPs under a static magnetic field. Simulation results show that, the degree and speed of assembly is proportional to the field strength. The BMM achieves the maximum speed of 161.7 µm s-1 and accurate positioning control under a rotating magnetic field with less than 4% deviation. Importantly, the locomotion analyses of BMMs demonstrate the frequency-dependent synchronization under 8 Hz and asynchronization at higher frequencies due to the increased drag torque. The BMMs can deliver and release thrombolytic drugs via magneto-collective control, which is promising for ultra-minimal invasive thrombolysis.