Solitary and Collective Motion Behaviors of Microrobots under the Coupling of Multiple Light Fields.

Due to their fascinating solitary and collective behavior, photochemical microrobots have attracted extensive attention from researchers and have obtained a series of outstanding research progress in recent years. However, due to the limitation of using a single light source, the realization of reconfigurable and controllable motion behaviors of the photochemical microrobot is still facing a series of challenges. To release these restrictions, we reported a multi-light-field-coupling-based method for driving the photochemical microrobot or its swarm in a regulatable manner. Here, we first designed a control system for coupling multiple light sources to realize the programmable application of four light sources in different directions. Then a TiO2-based photochemical microrobot was prepared, with its surface electric field distribution under different lighting conditions estimated by modeling-based simulation, where the feasibility of regulating the microrobot's motion behavior via the proposed setup was verified. Furthermore, our experimental results show that under the action of the compound light fields, we can not only robustly control the motion behavior of a single TiO2 microrobot but also reconfigure its collective behaviors. For example, we realized the free switching of the single TiO2 microrobots' movement direction, and the controllable diffusion, aggregation, the locomotion and merging of TiO2 microrobot swarms. Our discovery would provide potential means to realize the leap-forward control and application of photochemical microrobots from individuals to swarms, as well as the creation of active materials and intelligent synthetic systems.