Simultaneous crosslinking induces macroscopically phase-separated microgel from a homogeneous mixture of multiple polymers

This paper reports a unique phase separation behavior, a simultaneous-crosslinking-driven phase separation in co-gelation (SPSiC) core–shell microgel that spontaneously forms from a homogeneous pre-gel solution of multiple polymers. The SPSiC microgel, composed of an alginate shell and an N-isopropylacrylamide (NIPAM) core, were synthesized by a single fabrication step wherein a mixed pre-gel solution of sodium alginate and NIPAM monomer was ejected by centrifugation with photo-polymerization and ion crosslinking instantaneously. Phase separation was modeled by varying the degree of polymerization and the size of the polymer chain. Moreover, an implantable, multi-functional drug delivery system combined with a transdermal glucose sensor was demonstrated with core–shell Janus SPSiC microgels. This work shows a macroscopic phase separation behavior, which occurs during the gelation process, and also provides a simple and unique methodology to create multifunctional bio-microprobes.