Design and Applications of Liquid Crystal Biophotonic Sensors for Ion Detection

Abstract

Liquid crystals (LCs) are nanophotonic materials which can interact with light in the molecular scale. While the LCs are widely used in various displays, last decade has witnessed emerging applications of the LCs for nondisplays. Based on the unique stimuli–responsive property and optical property, the applications of the LCs in the field of sensors are widely explored. In addition, ions are widely distributed in nature and bionts, playing critical roles in many physiological activities and ecological cycles. Appropriate amount of ions is beneficial to the human body, while the excess ions can cause irreversible damages. As a result, a variety of LC sensors are proposed to detect the ion concentration in both body fluids and water samples. This article reviews the design principles, applications, and existing problems of the LC ion sensors. The geometries, alignments, and optical signals of the sensors, which can guide the design of the devices, are first discussed. Afterward, two types of LC ion sensors aiming at detecting metal ions and nonmetallic ions, respectively, are illustrated. Finally, the current challenges and potential development directions of the LC ion sensors are introduced briefly.

Chemically and biochemically responsive liquid crystal polymer networks and elastomers

“…Other examples of sensors using similar concepts have also been reported. 46,47 Chemically responsive LC polymers have also been used to detect solvents that do not have a basic or acidic character. Kuo and co-workers adopted a hydrogen-bonded cholesteric formulation for use in alcohol detection.…”

State-of-the-Art Development in Liquid Crystal Biochemical Sensors

“…Although many methods have been used to detect metal ions with good accuracy, meeting industry standards (e.g., atomic absorption spectrometry, fluorescence spectrometry, electrochemical analysis), they generally require large and expensive equipment, as well as complex and time-consuming sample pretreatment processes. In contrast, LC-based metal ion sensors provide a sensitive, simple, fast, and low-cost method [ 22 ]. Table 1 summarizes the LC-based metal ion sensors developed in recent years.…”

“…Hence, LC shows great potential for toxicant detection, environmental monitoring, and disease diagnosis. To date, a number of groups have reviewed the general components and applications related to LC-based biosensors [ 20 , 21 , 22 , 23 ]. There are still some missing parts that are worth discussing, such as LC sensing of chemical compounds and machine-learning-assisted LC sensing technology.…”