Rotating-liquid-based hydrogel bead generator

Hydrogel beads are widely used in various applications, but producing such beads often requires complicated devices. Instead, we propose an easy-to-adopt, cost effective, open source hydrogel bead generator. This generator consists of two modules. The first module rotates two immiscible liquids in rigid body motion: mineral oil as the continuous phase (CP) liquid on top, and a hydrogel cross-linking (CL) liquid at bottom. The second module injects a hydrogel pre-polymer solution as the dispersed phase (DP) liquid into the rotating CP liquid. As the DP liquid flows out of a syringe needle, its drops are pinched off by the shear force from the CP liquid, and move with the CP liquid while settling down. When the drops enter the CL liquid, they become hydrogel beads. Experiments using water and mineral oil showed that the size of produced drops could be controlled by adjusting the flow speed of the CP and DP liquids. A demonstration using alginate showed that the proposed generator could successfully create alginate gel beads of uniform size and shape.