Torres Juan Carlos, García-Cámara Braulio, Pérez Isabel, Urruchi Virginia, Sánchez-Pena José Manuel
Displays and Photonic Applications Group, Department of Electronic Technology, Carlos III University of Madrid, Avenida de la Universidad 30, Leganés E28911, Spain.
Sensors (Basel). 2015 Mar 6;15(3):5594-608. doi: 10.3390/s150305594.
The main characteristic of liquid crystals is that their properties, both electrical and optical, can be modified through a convenient applied signal, for instance a certain voltage. This tunable behavior of liquid crystals is directly related to the orientation of their nanometric components with respect to a director direction. However, the initial alignment is a fabrication-dependent parameter and may be either planar or homeotropic. In addition, the strong dependence of the properties of liquid crystals with the temperature is well known and widely used for several temperature sensors. This dependence is produced by the influence of the temperature on the ordering of the molecules. In this work, we have studied the temperature dependence of the electric properties of a liquid crystal cell, in particular the dielectric permittivity, with the temperature as a function of the initial alignment set during the fabrication process. Starting from experimental measurements, an equivalent circuit model including the temperature dependence has been proposed. We have observed that a good linearity in a wide temperature range is provided at a suitable exciting frequency. Finally, a proper conditioner circuit is proposed as a powerful tool for linear and high sensibility temperature measurement.
液晶的主要特性在于其电学和光学性质均可通过施加合适的信号（例如一定电压）来改变。液晶的这种可调行为直接与其纳米级组件相对于指向矢方向的取向有关。然而，初始取向是一个依赖于制造工艺的参数，可能是平面取向或垂直取向。此外，液晶性质对温度的强烈依赖性是众所周知的，并被广泛应用于多种温度传感器。这种依赖性是由温度对分子有序性的影响产生的。在这项工作中，我们研究了液晶盒电学性质的温度依赖性，特别是介电常数，其中温度是制造过程中设定的初始取向的函数。从实验测量出发，提出了一个包含温度依赖性的等效电路模型。我们观察到，在合适的激励频率下，在很宽的温度范围内都具有良好的线性度。最后，提出了一种合适的调节电路，作为线性和高灵敏度温度测量的有力工具。
