Fabrication of colorful colloidal photonic crystal fibers via a microfluidic spinning technique

A new strategy is demonstrated to fabricate colorful colloidal photonic crystal fibers (CPCFs) by microfluidic spinning technique. We employed a homogeneous mixture of viscous polyvinylpyrrolidone (PVP) and monodisperse SiO2 particles to fabricate micro-scale fibers. By manipulating the motor speed of the microfluidic spinning machine, various diameter fibers were produced efficiently. Monodisperse SiO2 particles can assemble into photonic crystal structures by removing PVP through calcination and show bright structural colors, which can be easily adjusted by changing the sizes of SiO2 colloids. In addition, we successfully fabricated humidity-sensitive polyacrylamide (PAM)/CPCFs, which exhibited obvious color response to the environmental humidity. The chromatic transitions span over almost the whole visible spectrum. This work might promote the development of colorful colloidal photonic crystal fibers via a microfluidic spinning technique.