Chiral Photonic Crystalline Microcapsules with Strict Monodispersity, Ultrahigh Thermal Stability, and Reversible Response

Abstract

Tunable photonic crystals (TPCs) reflecting selected wavelengths of visible light and responding to external stimuli are widely applied to fabricate smart optical devices. Chiral nematic liquid crystals (CNLCs) possessing response to temperature, electric field, and magnetic field are considered as one-dimensional TPCs. The encapsulation of CNLCs provides responsive photonic devices with stand-alone macroscopic structure and excellent processability. However, when CNLCs as cores are wrapped by polymeric shells to form core-shell structured microcapsules, the polydispersity of microcapsule size, the irregular spatial geometry, and the low thermal stability inevitably result in a deterioration of the optical performance and limited application at high temperatures. Herein, a combination of microfluidic emulsification and interfacial polymerization is employed to fabricate polymer wrapped photonic crystalline microcapsules (PWPCMs). The sizes and reflected colors of PWPCMs can be simultaneously controlled by adjusting the flow rates in the microfluidic chips. PWPCMs possess strictly monodispersed sizes with coefficients of variation less than 1%. The free-standing PWPCMs have high thermal stability. The deformation temperature of PWPCMs is as high as 210 °C. The colored PWPCMs also exhibit a reversible thermochromic property between the chiral nematic phase and the isotropic phase. The highly stable and tunable PWPCMs provide new opportunities for a wide range of photonic applications, including smart optical window, tunable microlasers, responsive microsensors, and various photonic devices.

Capillary-Based Microfluidic Fabrication of Liquid Metal Microspheres toward Functional Microelectrodes and Photothermal Medium

“…The production of LM microspheres by molding is not dynamically adjustable and very time-consuming. The microfluidic technology has been proven as a fast, high throughput, and highly controllable methodology to produce liquid droplets or emulsions for chemical, biochemical, and materials science applications. − Very recently, flow-focusing microfluidic chips have been used to produce LM microspheres. Theoretically, flow-focusing chips drive the bulk LM fluid (dispersed phase) and another immiscible fluid (continuous phase) through a small orifice in the microfluidic channels.…”

Shell Formation Mechanism for Direct Microencapsulation of Nonequilibrium Pure Polyamine Droplet

“…To date, the encapsulation techniques have been diversified to broaden the range of substances that can be encapsulated for various functional materials. − However, it is still a challenge for the traditional encapsulation techniques to encapsulate polyamine, attributed to its high reactivity, amphiphilicity, and good solubility in water and most organic solvents. Currently, the explored three main strategies to enwrap polyamines include using hollow microspheres to carry polyamine, encapsulating specially selected polyamines using traditional techniques, and tailoring the physicochemical properties of the core targets containing polyamine for encapsulation.…”

Geminate labels programmed by two-tone microdroplets combining structural and fluorescent color

“…One of the intriguing features of CLCs is to selectively reflect the circularly polarized light, according to Bragg's law, with the same handedness as the helix. This unique soft photonic crystal material can be easily prepared and constructed into multidimensional architectures from planar to spherical periodic structures [21][22][23][24][25][26][27][28][29][30][31][32][33] .…”