Janus photonic microobjects have shown great potential in various fields due to their anisotropic shapes and tunable optical properties. Microfluidics is useful for constructing such photonic microobjects. The traditional method of injecting different colloidal photonic streams toward anisotropic multiple stopband photonic microobjects involves complicated and time-consuming procedures. Herein, an easy yet effective approach to fabricate Janus photonic microobjects with dual stopbands from a single stream of photonic components is proposed. A microfluidic device is used to prepare bullet-like, single-stopband photonic microobjects by virtue of the microchannel’s confinement effect. Both the size and shape are readily regulated by adjusting the flow rate of the continuous phase. Under the protection of the desired region of the photonic microobjects with polystyrene (PS) film or silicone tube, the other region is selectively etched to generate a new photonic part. The Janus photonic microobjects with dual stopbands are achieved thereby. Precision control of the protection position of the single-stopband photonic microobjects provides the flexibility to achieve photonic microobjects with various segmental combinations. The porous structure at the etched region is conducive to further functionalization, for example, fluorescence performance, by filling polymers. The resultant photonic microobjects with strong information-encoding characteristics are promising in display and anticounterfeiting.
Double bandgap photonic crystals (PCs) exhibit significant potential for applications in various color display-related fields. However, they show low color saturation and inadequate color modulation capabilities. This study presents a viable approach to the fabrication of double bandgap photonic inks diffracting typical secondary colors and other composite colors by simply mixing two photonic nanochains (PNCs) of different primary colors as pigments in an appropriate percentage following the conventional RGB color matching method. In this approach, the PNCs are magnetically responsive and display three primary colors that can be synthesized by combining hydrogen bond-guided and magnetic field (H)-assisted template polymerization. The as-prepared double bandgap photonic inks present high color saturation due to the fixed and narrow full-width at half-maxima of the parent PNCs with a suitable chain length. Furthermore, they can be used to easily produce a flexible double bandgap PC film by embedding the PNCs into a gel, such as polyacrylamide, facilitating fast steady display performance without the requirement of an external magnetic field. This research not only presents the unique advantages of PNCs in constructing multi-bandgap PCs but also establishes the feasibility of utilizing PNCs in practical applications within the fields of anti-counterfeiting and flexible wearable devices.
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