Swarming magnetic photonic‐crystal microrobots with on‐the‐fly visual pH detection and self‐regulated drug delivery

Swarming magnetic micro/nanorobots hold great promise for biomedical applications, but at present suffer from inferior capabilities to perceive and respond to chemical signals in local microenvironments. Here we demonstrate swarming magnetic photonic‐crystal microrobots (PC‐bots) capable of spontaneously performing on‐the‐fly visual pH detection and self‐regulated drug delivery by perceiving local pH changes. The magnetic PC‐bots consist of pH‐responsive hydrogel microspheres with encapsulated one‐dimensional periodic assemblies of Fe 3 O 4 nanoparticles. By programming external rotating magnetic fields, they can self‐organize into large swarms with much‐enhanced collective velocity to actively find targets while shining bright “blinking” structural colors. When approaching the target with abnormal pH conditions (e.g., an ulcerated superficial tumor lesion), the PC‐bots can visualize local pH changes on the fly via pH‐responsive structural colors, and realize self‐regulated release of the loaded drugs by recognizing local pH. This work facilitates the development of intelligent micro/nanorobots for active “motile‐targeting” tumor diagnosis and treatment. image