The Study Of Anchoring Properties Of Sensitive Self-assembled Film

With advances in technology, chemical sensor is developing towards democratization and commoditization. As we know, liquid crystal had already been widely used in electronic display. In recent years, people attempted to introduce liquid crystal into chemical sensing field to build liquid crystal sensors. These sensors have advantages of fast, simple, low cost, compact and convenient and they have got very good results in life science and environmental monitoring studies. However, reported liquid crystal chemical sensing technologies based on optical change have problems of insufficient sensitivity when detecting low concentration of targeted analytes. So to develop new liquid chemical sensors that have better sensitivity and detectability has become a research hotspot. This article proposed new liquid crystal sensors based on anchoring change. Specific works were done as following:1. A new liquid crystal sensor model based on anchoring change was proposed through studying anchoring properties of sensitive self-assembled film on double-sided electrodes. Liquid crystal cells were made with substrate surfaces coated by different concentrations of cetyltrimethyl ammonium bromide (CTAB), then same cell was divided into two parts with one part filled with nematic liquid crystal(NLC) and the other part with cholesteric liquid crystal(CLC). In NLC part polar anchoring energy was measured using strong electric field method and the relationship between CTAB's concentration and surface's anchoring energy was studied. In CLC part the stability of focal conic texture in high temperature was measured and its relationship between anchoring energy and analyte concentration were determined. Results showed that the higher was the concentration of CTAB, the larger was the polar anchoring energy on the surface, the more stability was focal conic texture in high temperature. These results realized using new optical method to detect the concentration of targeted analytes, providing rapid methods for biochemical detection in many fields.2. A new liquid crystal sensor model based on anchoring change was proposed through studying anchoring properties of sensitive self-assembled film on in-plane electrodes. Different anchoring conditions were created by using different concentrations of CTAB. liquid crystal cells were made with substrate surfaces coated by different concentrations of CTAB. After liquid crystal 5CB was filled in, each cell's optical response was observed with electric field applied under polarized optical microscope and their threshold voltage characteristics were measured to characterize the magnitude of anchoring energy jointly. Results showed that the larger was anchoring energy on the surface, the larger was the threshold voltage. The outstanding feature of this sensor is that it can directly contact with liquids and gases, realizing real-time detection. So it has potential applications in water quality test, biochemical detection etc.