Microfluidic Fabrication and Thermoreversible Response of Core/Shell Photonic Crystalline Microspheres Based on Deformable Nanogels

摘要

Soft photonic crystals (PC) are more appealingndue to the responsiveness of the building blocking-deformablennanoparticles to the external stimuli. In this report, wendemonstrate, for the first time, the generation of soft core/shellnPC microspheres through a combination of a microfluidicntechnique, encapsulation of well-ordered temperature responsivenpolymer nanogels suspension, and photopolymerization ofna transparent shell resin. This strategy not only ensures thenmonodispersity of core/shell PC microspheres, but alsonprecisely controls their size, shell thickness, and opticalnproperties by simply adjusting the flow rate ratio and massnfraction of the nanogels. More interestingly, the intensity of the reflection spectra of the crystalline nanogel arrays in the core cannbe modulated reversibly by controlling the shell thickness or the temperature. As a result of their symmetric structure, thenresulting PC microspheres exhibited excellent structural colors and photonic band gaps for normal incident light independent ofnthe position on the spherical surface. Multifunctional PC microspheres can also be generated by simply dispersing functionalnspecies together with the nanogels. This core/shell PC microsphere with tunable shell thickness and reversible thermoresponsencould be significant for potential applications in the fields of chemical/biological sensors, display, encoding, and optical switching.