Liquid-liquid phase separation is a fascinating and ever-evolving phenomenon that has captured renewed attention, particularly in the fields of biology and material synthesis. Our focus has been on exploring the co-flow of a nonequilibrated aqueous two-phase system within a planar flow-focusing microfluidic device. To achieve this, we leveraged polymerization as a means of generating intricately structured microfibers. This innovative approach holds great promise for advancing our understanding of phase separation dynamics and opens up exciting possibilities for material fabrication.