High-Speed Bioassembly of Cellular Microstructures with Force Characterization for Repeating Single-Step Contact Manipulation

In vitro tissues are significant biological substitute for drug test, cell morphogenesis exploration and organ transplantation. In this letter, a novel microrobotic bioassembly method is proposed to engineer 3-D cellular structure, which can be utilized to culture in vitro tissue with microstructural features. A microrobotic system is set up under optical microscope with 30 nm positioning resolution. To assemble cellular micromodules, the system repeats a programmed single-step contact motion with one manipulator, which effectively avoids human intervention and frequent alignment of micromanipulators. The contact force is analyzed and the system is modeled to be a cantilever handing beam for dynamic force characterization. Through the characterization, we figure out the key parameter as the stiffness of micromanipulator at contact point, which influences assembly success rate. After the calibration of stiffness, the high-speed assembly of cellular structure is performed with an assembly speed of 20 micromodules/min. Finally, the 3-D cellular structure incorporating vascular-like microtube is engineered for the fabrication of in vitro micro tissues.