Three-dimensional magnetic assembly of alginate microfibers using microfluidic “printing” method

Due to the poor controllability in hydrogels, Hydrogels-based assembly to form larger 3D complex shapes is still a big challenge. In this paper, we have reported a novel “bottom-up” method to fabricate three-dimensional (3D) magnetic alginate microfibers (MAMs) assemblies with complex shapes. Specifically, Alginate microfibers encapsulating Fe₃O₄ magnetic nanoparticles (MNs) and fibroblasts (NIH/3T3) have been spun using microfluidic method with “pinch-off” scheme. Experimental results show that the MAMs can respond quickly to the magnetic field, enabling their enhanced controllability. The magnetic assembly system is constructed by PDMS microfluidic device, 3D supporting model adhered on the bottom surface of dish filled with deionized water and magnet. The microfluidic “printing“ and magnetic deposition in magnetic assembly process are experimentally demonstrated, respectively. Because of magnetic field, the complex assembly shapes can be fabricated just by moving the microfluidic device in a plane. To match well with the shape of supporting model and to keep a stable assembly structure, the secondary cross-linking method is employed. From the LIVE/DEAD assay, cells can survive well during the magnetic assembly process.