Magnetic-Directed Manipulation and Assembly of Fragile Bioartificial Architectures in the Liquid-Liquid Interface

Assembling has been regarded as one of the most potential methods for fabricating complex structures with better performance and richer features, especially at nano/micro scale. Despite the recent achievement in micromanipulation and assembly, including self-assembling, mechanical micromanipulator, and noncontact operation, the manipulation and assembly of flexible and fragile microstructures in an enclosed environment for biomedical applications are still challenging. In this work, we proposed a method to assemble untethered and fragile hydrogel structures (building units) in the liquid-liquid interface by a magnetic microcapsule-robot (MMc-robot). Different from the conventional magnetic robot, a semipermeable alginate-chitosan-alginate layer is adopted to encapsulate magnetic particles to make the MMc-robot biocompatible, during which, the designed lock-and-key shape not only allows the grabbing between MMc-robot and building units but also ensures the reliable forward force as well as steering torque transmission. To constrain the building units in the same plane while keeping the structural integrity and movement flexibility, we conduct the experiment in the liquid-liquid interface. Moreover, the corresponding mechanical analysis, dynamic modeling, and control strategy are provided for the manipulation and assembly of units. The successful results in magnetic-directed assembly of untethered and fragile microstructures in the liquid-liquid interface verify the feasibility as well as practicality of the proposed manipulation and assembling methods. This research provides a new prospect for the manipulation and assembly of flexible bioartificial architectures, which shows promise in 3-D complex structures fabrication from biomimetics to tissue engineering.