Reconfiguring Self-Assembly of Photoresponsive Hybrid Colloids.

The reconfigurable self-assembly of colloidal particles allows the bottom-up creation of adaptive materials, yet significant challenges remain. Here, we demonstrate a synthesis of photoresponsive Fe 2 O 3 /polysiloxane hybrid colloids that perform a dynamically reconfigurable self-assembly. Such self-assembly is due to chemical gradients originating from the decomposition of H 2 O 2 by the Fe 2 O 3 component under UV irradiation. The morphology of the self-assembly includes chains and flower-structures, where the chains can be transformed in situ into flower-like structures with decreasing UV intensity. The flower-structures can be further switched by applying an external magnetic field, leading to orientationally ordered clusters. This, interestingly, leads to an asymmetrical chemical gradient surrounding the assemblies, and transforms the cluster into a micromotor exhibiting a self-propulsion steerable by the magnetic field. Our findings demonstrate a new possibility to control and reconfigure the self-assembly of colloids, which offers an important pathway for fabrications of adaptive and smart materials at the microscale.