Investigation On The Annular Structural Colors From Bowl-like Photonic Microshells Of Cholesteric Liquid Crystals

Cholesteric liquid crystals can selectively reflect incident circularly polarized light as one-dimensional photonic crystal material with periodic helix structure,so it can dynamically adjust colors,which makes it a candidate for countless different photon application.Compared with traditional planar cholesteric liquid crystal materials,cholesteric droplets or photon microshells generated by emulsification have attracted more attention due to their unique optical reflection modes.Microfluidic technology has become a general method for preparing double emulsions of uniform size,with broad application prospects.Many unique and attractive observations have been made in the uniform monodisperse cholesteric liquid crystal droplets and microshells prepared by the microfluidic method,indicating that it has great potential in generating vivid,diverse and complex optical patterns with structural colors.Three reflection modes of photon microshells have been observed so far,including central reflection of the photonic structure,cross communication between adjacent cholesteric liquid crystal photon microshells,and internal reflection of the microshells.Among them,the reflection inside the microshell is only recently observed in the asymmetric cholesteric liquid crystal photon microshell.The annular structural color is generated by the internal reflection,and the reflection angle follows Bragg's law.This novel and unique reflection mode is well worth of further research.In this study,a polymerizable cholesteric liquid crystal water-in-oil-in-water(W/O/W)double emulsion core-shell structure was prepared using a glass capillary microfluidic device,and the osmotic pressure was used to form a shrivelled bowl-like structure.The selective Bragg reflection in the bowl-like structure shows a new type of structural color ring photon pattern.By adjusting the osmotic pressure and the pitch of the cholesteric liquid crystals,a controllable generation of this type of pattern was realized.In addition,by introducing colloidal photonic crystal suspension into the inner phase,the factors causing the color of the ring structure were further explored,and more complex and interesting optical phenomena were discovered.