Biomimetic Solid-Liquid Transition Structural Dye-Doped Liquid Crystal/Phase-Change-Material Microcapsules Designed for Wearable Bistable Electrochromic Fabric

Reflectivity and Angular Anisotropy of Liquid Crystal Microcapsules with Different Particle Sizes by Complex Coalescence

Cholesteric liquid crystal microcapsules (CLCMs) are used to improve the stability of liquid crystals while ensuring their stimulus response performance and versatility, with representative applications such as sensing, anticounterfeiting, and smart fabrics. However, the reflectivity and angular anisotropy decrease because of the anchoring effect of the polymer shell matrix, and the influence of particle size on this has not been thoroughly studied. In this study, the effect of synthesis technology on microcapsule particle size was investigated using a complex coalescence method, and the effect of particle size on the reflectivity and angular anisotropy of CLCMs was investigated in detail. A particle size of approximately 66 µm with polyvinyl alcohol (PVA, 1:1) exhibited a relative reflectivity of 16.6% and a bandwidth of 20 nm, as well as a narrow particle size distribution of 22 µm. The thermosetting of microcapsules coated with PVA was adjusted and systematically investigated by controlling the mass ratio. The optimized mass ratio of microcapsules (66 µm) to PVA was 2:1, increasing the relative reflectivity from 16.6% (1:1) to 32.0% (2:1) because of both the higher CLCM content and the matching between the birefringence of the gelatin-arabic shell system and PVA. Furthermore, color based on Bragg reflections was observed in the CLCM-coated ortho-axis and blue-shifted off-axis, and this change was correlated with the CLCM particle size. Such materials are promising for anticounterfeiting and color-based applications with bright colors and angular anisotropy in reflection.

Progress in Fabrication and Applications of Cholesteric Liquid Crystal Microcapsules

Liquid crystals (LCs) are well known for inherent responsiveness to external stimuli, such as light, thermal, magnetic, and electric fields. Cholesteric LCs are among the most fascinating, since they possess distinctive optical properties due to the helical molecular orientation. However, the good flow, easy contamination, and poor stability of small-molecule LCs limit their further applications, and microencapsulation as one of the most effective tools can evade these disadvantages. Microencapsulation can offer shell-core structure with LCs in the core can strengthen their stability, avoiding interference with the environment while maintaining the stimuli-responsiveness and optical properties. Here, we report recent progress in the fabrication and applications of cholesteric LC microcapsules (CLCMCs). We summarize general properties and basic principles, fabrication methods including interfacial polymerization, in-situ polymerization, complex coacervation, solvent evaporation, microfluidic and polymerization of reactive mesogens, and then give a comprehensive overview of their applications in various popular domains, including smart fabrics, smart sensor, smart displays, anti-counterfeiting, information encryption, biomedicine and actuators. Finally, we discuss the currently facing challenges and the potential development directions in this field.

GST plasmonic gap structure investigation as a switch and sensor

In this paper, a plasmonic perfect absorber that consists of a gold rectangular bar with three gaps is investigated as a switch and sensor in the near-infrared region. Phase change material germanium-antimony-tellurium (GST) is utilized in two gaps to perform the switching capability with a high extinction ratio of 18.49 dB. In addition, the sensing performance of the structure for detection of a solution of glucose in water and diagnosis of different cancer cells is studied. The best sensitivity of 1504 nm/RIU is obtained for detection of the PC12 cancer cell, and the figure of merit of the structure is around 17R I U -1.

Fluorescent Dye-Doped Brightening Polymer-Stabilized Bistable Cholesteric Liquid Crystal Films

Brightening polymer-stabilized bistable cholesteric liquid crystal (PSBCLC) films with doped fluorescent dyes were prepared using the polymerization-induced phase separation (PIPS) method. The transmittance performance behavior of these films in both states (focal conic and planar) and absorbance change in multiple dye concentrations were studied using a UV/VIS/NIR spectrophotometer. The change occurring in dye dispersion morphology with different concentrations was obtained by means of the polarizing optical microscope. The maximum fluorescence intensity of different dye-doped PSBCLC films was measured using a fluorescence spectrophotometer. Moreover, the contrast ratios and driving voltages of these films were calculated and recorded to demonstrate film performance. Finally, the optimal concentration of dye-doped PSBCLC films with a high contrast ratio and a relatively low drive voltage was found. This is expected to have great potential applications in cholesteric liquid crystal reflective displays.

3D-Printed Flexible Phase-Change Nonwoven Fabrics toward Multifunctional Clothing

Functional phase-change fabrics hold great promise as wearable clothing. However, how to enable a phase-change fabric with the combined features of excellent structural flexibility and robustness, integrated multifunctionality, superior stability, and durability, as well as facile and scalable manufacturing, still remains a significant challenge. Herein, we demonstrated a scalable and controllable three-dimensional (3D) printing strategy for manufacturing flexible, thin, and robust phase-change nonwoven fabric (PCNF), with abundant and regular breathable pores as well as uniform and tight embedment of highly interconnected single-walled carbon nanotubes (SWNTs) into hydrophobic filaments built by intertwining solid-solid phase-change polymer chains together. The remarkable architectural features enabled an integral whole of the fabric, ready air exchange, superior water impermeability, highly efficient heat harvesting and storage, and effective absorption and reflection of electromagnetic waves, thereby delivering an exceptional combined function of breathability, waterproofness, thermal regulation, and radiation resistance, and meanwhile featuring superior thermal stability and outstanding resistance to stretching/folding fatigue even at cycles up to 2000. This work sheds light on effective strategies for manufacturing wearable phase-change fabrics with multifunctionality and high stability in a scalable manner toward future uses.