Fig. 5: Maze navigation and drug delivery by microbot collectives with different assembled morphologies.

a Illustration of experimental steps for accurate delivery of doxorubicin hydrogel block. The connected three microbots are initially located outside the entrance to the maze and are assembled in a 180° method so that they can be pulled through a narrow channel at the entrance using a magnetic field. Once inside the maze, they are reconfigured into a C-shaped morphology by switching from a 180° assembly method to a 90° assembly method under the coordinated control of the magnetic and light fields, allowing them to carry a carrier (red). The carrier is prepared by immersing a cubic hydrogel block processed by TPP in DOX solution (5 mg mL^-1) for 1 h to load drugs onto the carrier. After the carrier is gripped, it is transported to the targeted position using a magnetic field. Afterwards, they are reconfigured into the I-shaped morphology in order to release the carrier. Finally, they pass through the narrow passage at the exit of the maze. b Optical images show the delivery process of doxorubicin hydrogel block. The images from each location have been stitched together to demonstrate the full path. c Fluorescence comparison images show the fluorescence changes of HeLa cells cultured in square micro-fences with and without doxorubicin hydrogel block inside in a time span of 12 h. d Quantitative statistics of fluorescence intensity of HeLa cells with and without doxorubicin hydrogel block inside. The error bars represent the standard error of the measurements (n = 3).