Liquid Crystals for Advanced Smart Devices with Microwave and Millimeter‐Wave Applications: Recent Progress for Next‐Generation Communications

Abstract

Liquid crystals (LCs) technology have a well‐established history of applications in visible light, particularly in the display industry. However, with the rapid growth in communication technology, LCs have become a topic of current interest for high‐frequency microwave (MW) and millimeter‐wave (mmWave) applications due to promising characteristics such as tunability, continuous tuning, low losses, and price compatibility. To improve the performance of future communication technology using LCs, it is not sufficient only with the perspective of radio‐frequency (RF) technology. Therefore, it is imperative to understand not only the novel structural designs and optimization of MW engineering but also the perspective of materials engineering when implementing advanced RF devices with maximum performance for next‐generation satellite and terrestrial communication. Herein, based on advanced nematic LCs, polymer‐modified LCs, dual‐frequency LCs, and photo‐reactive LCs, this article summarizes and examines the modulation principles and key research directions for the design strategies of LCs for advanced smart RF devices with improved driving performance and novel functionality. Furthermore, the challenges in development of state‐of‐the‐art smart RF devices that use LCs are discussed.

Holographic Plastics with Liquid Crystals

“…Therefore, it is highly demanded to integrate different security functions in one element. The combination of holographic and photoluminescent patterns offers great versatility as LCs allow for added functions such as the temperature, electric field, and light and polarization responsiveness. ,− However, it remains a formidable difficulty to enable integration of these functions in reflection holograms due to the lack of deep insights into the formulation processes.…”

“…It is reasonable to break through the bottleneck by introducing liquid crystals (LCs), which are a fluidic soft matter that maintains crystal order and shows unique characteristics of low viscosity, high refractive index, and fast stimuli responses. − Therefore, holographic plastics with LCs have attracted considerable attention since the first work in 1992. ,, Another interesting feature is that the holographic plastics based on LCs are very sensitive to the polarization state of the probe beam due to the inherent anisotropy and preferential orientation of LCs. − This feature may facilitate dynamic electro-optic modulation in display systems. , However, despite extensive research on this area for 30 years, there are still several major challenges. (1) From a materials scientist’s perspective, how does the refractive index modulation manipulate the light propagation?…”

Liquid Crystals for Luminescent Concentrators: A Review

“…A host material that can impose a macroscopic orientational ordering on an asymmetricshaped dye is a nematic LC, whose molecules align along a pseudo-unit vector known as the director [33][34][35]. Liquid crystals have been tremendously successful in flat-panel display technologies [36] and have been/are being considered for a broad range of alternative applications, including high-frequency technologies [37,38], biological systems [39], opto-electronic applications [40], communication engineering [41,42], and much more.…”

Novel maleic anhydride derivatives: liquid crystalline materials with enhanced mesomorphic and optical characteristics

“…Each liquid crystal assembly that makes up a display pixel is governed by its own electromagnetic field. The field modifies the liquid crystals' orientation, which alters how much light can pass through them and result in the images you see on a screen (Alamro et al, 2021;Gomha et al, 2021;Abdou et al, 2022;Alamro et al, 2022;Chi et al, 2022;Uchida et al, 2022;Wang et al, 2022;Yin et al, 2022;Behera et al, 2023;Ma et al, 2023).…”