Fabrication of functional hydrogel microbeads utilizing non-equilibrium microfluidics for biological applications

In this report, we present two processes to fabricate unique hydrogel beads, (1) yarn-ball-shape beads and (2) extremely-small beads, utilizing non-equilibrium microfluidics. First, to prepare the yarn-ball-shape microbeads, an incompletely-gelled Ca-alginate hydrogel fiber in a microchannel was cut into pieces and incorporated into water-in-oil droplets. Then, non-equilibrium W/O droplets, composed of water containing hydrogel molecules as the disperse phase and a water-soluble organic solvent as the continuous phase, were used to prepare extremely small hydrogel Ca-alginate hydrogel beads (Φ = ~10 μm). As an application, high-density cell cultivation (~1 × 10⁸ cells/mL) in the yarn-ball-shape hydrogel beads was demonstrated. These hydrogel beads would be highly useful as unique carriers or matrices for biological immobilization, cultivation, and transplantation.