text: Other photoinitiated free radical polymerization reactions can also be used for fiber production. In this case, the shealth fluid was only used to separate the core fluid from the tube wall. Also, to achieve the solidification rapid enough, a more concentrated monomer solution was usually used.
  An example would be the production of 4-hydroxybutyl acrylate fiber reported by Beebe et al. The microfluid device they used was built with ethylvinyl acetate caplliary and PDMS rubber. The core fluid was a mixture of [https://pubchem.ncbi.nlm.nih.gov/compound/75588 4-hydroxybutyl acrylate], acrylic acid, ethyleneglycol dimethacrylate (crosslinker), [https://www.chemicalbook.com/ChemicalProductProperty_EN_CB0439891.htm 2,2′-dimethoxy-2-phenyl-acetonephenone] (photoinitiator). The sheath fluid was only for separation. The crosslinked network was formed by free radical polymerization when the UV light met the core fluid.