Levit Shani L, Nguyen Jimmy, Hattrup Nicholas P, Rabatin Briget E, Stwodah Ratib, Vasey Christopher L, Zeevi Michael P, Gillard McKenna, D'Angelo Paola A, Swana Kathleen W, Tang Christina
Chemical and Life Science Engineering, Virginia Commonwealth University, Richmond, Virginia 23284-3028, United States.
U.S. Army Combat Capabilities Development Command Soldier Center, Natick, Massachusetts 01760, United States.
ACS Omega. 2020 Mar 24;5(13):7149-7157. doi: 10.1021/acsomega.9b03484. eCollection 2020 Apr 7.
Cholesteryl ester liquid crystals exhibit thermochromic properties related to the existence of a twisted nematic phase. When used in applications such as thermal mapping, a color change is often monitored by video cameras. Thus, quantitative methods to evaluate thermochromic behavior (e.g., blue-start, red-start, red-end, color play and bandwidth) from video analysis are desirable. However, obtaining quantitative color measurements from digital images remains a significant technical challenge, especially for highly reflective samples such as liquid crystals (for which ultraviolet-visible (UV-vis) reflectance spectroscopy is typically used). We developed a method to determine thermochromic properties from videos of liquid crystal cooling under polarized light microscopy. We relate observed color transitions to quantifiable changes in the cumulative color difference in the International Commission on Illumination (CIE) *** color space and validate this method with UV-vis reflectance spectroscopy. The measured thermochromic behavior and associated measurement uncertainties (coefficient of variations) were comparable to UV-vis reflectance measurements.
胆甾醇酯液晶表现出与扭曲向列相的存在相关的热致变色特性。当用于热成像等应用时，颜色变化通常由摄像机监测。因此，需要从视频分析中评估热致变色行为的定量方法（例如，蓝起始、红起始、红终点、颜色变化和带宽）。然而，从数字图像中获得定量颜色测量仍然是一项重大技术挑战，特别是对于高反射性样品，如液晶（通常使用紫外可见（UV-vis）反射光谱法）。我们开发了一种方法，用于从偏光显微镜下液晶冷却的视频中确定热致变色特性。我们将观察到的颜色转变与国际照明委员会（CIE）***颜色空间中累积色差的可量化变化相关联，并用UV-vis反射光谱法验证了该方法。测量的热致变色行为和相关测量不确定度（变异系数）与UV-vis反射测量相当。
