Study On Cholesteric Liquid Crystal System Used For Precise Temperature Measurement Of Human Body

The changing of body temperature may reflect one's healthy condition directly, so body temperature measurement is a common method of diagnosing. The clinical liquid crystal thermometer is a new, clean and green product, which is presently considered as one of the most powerful technology in the field of clinical temperature measurement and has been paid much attention. According to the thermochromism of cholesteric liquid crystal for showing the body temperature, liquid crystal clinical thermometer have been studied in this paper. On one hand, the system of liquid crystal mixture in application to clinical thermometer was explored and on the other hand the technical conditions of encapsulating liquid crystal materials were obtained. The research work will establish a foundation for industrialized production of clinical liquid crystal thermometer.First, cholesteric liquid crystal system which was applied to measure temperature in the range of body temperature was established in the thesis. That is cholesteryl oleyl carbonate: 75.7%(wt%); cholesteryl chloride: 17.7%(wt%); cholesteryl laurate: 6.60%(wt%). Furthermore a method that clearing point of temperature of liquid crystal mixture would be changed by adding an additive into the mixture has been developed. The results show 2# additive is feasible to applying to prepare clinical thermometer, and all the mixing liquid crystal systems of which the thermochromatic temperature degree of accuracy is 0.1℃in the range of body temperature have been obtained. Absolute errors were≤0.02℃and relative errors were≤0.06% between experimental value and calculated value of every clearing point of temperature, average absolute error was 0.008℃and average relative error was 0.02%. The linearity between the content of additive and the value of clearing point of temperature was very remarkably on the level ofα=0.01. This method has overcome the disadvantages of tradition methods, such as irregularly changing between the content of liquid crystal component and clearing point of temperature and the weaknesses of repeatability and visibility, and is obviously favorable in the field of clinical temperature measurement.Additionally it has been studied to microcapsulate technical of liquid crystal. Through emulsification and encapsulation tests, the effect of several factors such as emulsive temperature, emulsive speed, emulsive time, mass proportion between shell materials and core materials, encapsulating temperature, stirring speed, encapsulating pH value and diluted water quantity were explored in liquid crystal microcapsulating technology to obtain optimum conditions of emulsification and encapsulation. The result shows that the optimal conditions are emulsive temperature:55℃, emulsive speed:2000r/min, emulsive time:1h, encapsulating temperature: 65℃, diluted water quantity: 200ml/g, stirring speed: 400 r/min, encapsulating pH value: 4 and mass proportion between shell materials and core materials: 2:1. Mixing liquid crystal system has been succeeded in encapsulating and encapsulating efficiency was close up to 60%. Liquid crystal microcapsules have greatly strengthened on the aspect of stability, and the abilities of crystal-separating-out resisting and oxidative deterioration resisting have been obviously improved by microcapsulating.