Phototactic micromotor assemblies in dynamic line formations for wide-range micromanipulations

Abstract

In nature, living organisms can perform powerful cooperation by assembling themselves into defined formations. Enlightened by this, we herein demonstrate phototactic micromotor assemblies flocking in dynamic line formations for manipulating large cargoes in a wide range. When two independent stimuli, light and a static magnetic field, are applied to respectively trigger their phototactic propulsion and magnetic assembly, isotropic micromotors designed with a photocatalytic shell and magnetic core (i.e., magnetic bead@TiO₂ core–shell-structured micromotors, MB@TiO₂ MMs) can self-organize into phototactic assemblies flocking in line formations. After self-organization, they exhibit intriguing emergent behaviors that individuals do not have, such as dynamic assembly/disassembly, strong robustness, less trajectory tortuosity and orientation-dependent phototaxis. Benefiting from their emergent collective behaviors, the phototactic assemblies show excellent adaptivity to local landscapes and can accomplish wide-range cooperative manipulation (cooperative transport and “sweeping”) of large cargoes in both open and confined environments. The developed micromotor assemblies, due to their simple construction and easy light operation, are promising to serve as robust, reconfigurable and low-cost microrobot systems for microengineering and pathogen/toxin elimination.