A Novel High-Sensitivity, Low-Power, Liquid Crystal Temperature Sensor

A novel temperature sensor based on nematic liquid crystal permittivity as a sensing magnitude, is presented. This sensor consists of a specific micrometric structure that gives considerable advantages from other previous related liquid crystal (LC) sensors. The analytical study reveals that permittivity change with temperature is introduced in a hyperbolic cosine function, increasing the sensitivity term considerably. The experimental data has been obtained for ranges from -6 degrees C to 100 degrees C. Despite this, following the LC datasheet, theoretical ranges from -40 degrees C to 109 degrees C could be achieved. These results have revealed maximum sensitivities of 33 mV(rms)/degrees C for certain temperature ranges; three times more than of most silicon temperature sensors. As it was predicted by the analytical study, the micrometric size of the proposed structure produces a high output voltage. Moreover the voltage's sensitivity to temperature response can be controlled by the applied voltage. This response allows temperature measurements to be carried out without any amplification or conditioning circuitry, with very low power consumption.This work was supported in part by the Ministerio de Ciencia e Innovación of Spain (grant No.TEC2009-13991-C02-01) and Comunidad de Madrid (grant No. FACTOTEM2 S2009/ESP-1781)