Smart optical materials can adjust light refraction and scattering through external fields to modulate optical properties, such as color, transmittance, and polarization. They show important application potential as smart optical devices in the fields of information, energy and national defense. Among many smart optical materials, liquid crystals exhibit unique advantages due to their birefringence effect, multiple driving modes and easy industrialization. For example, reflective display devices based on cholesteric liquid crystal materials don’t need backlight, and have low energy consumption, light weight and flexibility, which can also be used for outdoor display. Liquid crystal can also control light transmittance, and thus it can be used to prepare smart windows for reducing glass buildings’ energy consumption, and serve as optical switchable window in conjunction with solar cells and other technologies. With the combination of liquid crystals, orientation and polarization technology, the refraction and polarization of light can be controlled through external fields, and electronically controlled optical elements can be prepared. Cholesteric liquid crystal can change color under temperature, humidity, gas or pressure stimulation, which is beneficial to preparing visual sensor. This article summarizes the application progress of liquid crystal materials in the four types of smart optical devices, reflective display, smart window, electronically controlled optical element and visual sensor. This review focus on the working mechanism of each application direction and discuss the advantages and disadvantages of current research. Finally, the prospects for the application development direction and challenges of liquid crystal materials in the field of smart optical devices are put forward. This article aims to provide a useful reference for the broader engineering applications of liquid crystals. © 2022 Cailiao Daobaoshe/ Materials Review. All rights reserved.
