In-ice polymerization for functional hydrogel microbead with flash freezing centrifugal microfluidic device

This paper describes a centrifuge-based fabrication method of microgel beads using flash freezing in liquid nitrogen and in-ice polymerization. Previously, materials for fabricating microgel beads with centrifugal microfluidic systems have been limited to only sodium alginate solution using rapid ionic cross-linking. By using our proposed method, the shape of beads can be defined by flash freezing of the ejected pre-gel microdroplets in liquid nitrogen and successive in-ice polymerization by UV irradiation. We succeeded in fabricating ethanol-responsive structural-color beads and confirmed their ethanol responsivity by exhibiting visible structural color change. Our fabrication method will expand the variety of materials for the centrifugal microfluidic microgel beads fabrication method and possible applications including biosensors and drug delivery systems.