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 theproposed 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.

I. Introduction

Assembling is a process where the independent and separate units will be reorganized and combined into an ordered structure. By assembling, the monotonous units can always change into a complex structure with better performance or richer features which make it become an essential fabrication process, especially at micro/nano scale. For instance, Draper et al. [1] achieved the control of photoconductivity in perylene bisimides by pH-directed self-assembling, VahidMohammadi et al. [2] manufacture the high-power and energy-density pseudocapacitive electrodes by assembling 2-D MXenes, Lin et al. [3] adopt the 2-D/3-D stacking assembling to improve the thermal stability in perovskite solar cells. Besides that, there are also many assembled microstructures applied in biomimetics and tissue engineering [4]–[7].