A Comparison of Chiral Nematic and Cholesteric Thermochromic Liquid Crystals for Use in a Light Transmission Based Temperature Sensing System

Abstract

This paper presents the results of a study performed to examine the effectiveness of several different formulations of thermochromic liquid crystal (TLC) material for use in a light transmission based temperature measurement system. We report on experiments performed on six different types of TLC material. We used a spectrophotometer to measure the percent of light transmitted through a layer of each TLC material for wavelengths from 400 to 700 nm as a function of temperature. We also applied TLC material directly onto electroluminescent lights and used a CCD camera to look at the intensity of red, green, and blue light transmitted through each layer as a function of temperature. We found that pure unsealed materials, both cholesteric and chiral nematic (non-sterol), are not suited for use in a temperature measurement system. They show little response to temperature and are difficult to work with due to their low melting point. On the other hand, the micro-encapsulated TLC slurry materials showed a large responsive range and were easier to work with than the pure materials. The chiral nematic material showed the largest sensitivity to temperature and was found to be more responsive than the cholesteric material.