Liquid crystal thermometer

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A liquid crystal thermometer or plastic strip thermometer is a type of thermometer that contains heat-sensitive (thermochromic) liquid crystals in a plastic strip that change color to indicate different temperatures. [1] Liquid crystals possess the mechanical properties of a liquid, but have the optical properties of a single crystal. Temperature changes can affect the color of a liquid crystal, which makes them useful for temperature measurement. The resolution of liquid crystal sensors is in the 0.1°C range. Disposable liquid crystal thermometers have been developed for home and medical use.

There are two stages in the liquid crystals, 1 - the hot nematic stage is the closest to the liquid phase where the molecules are freely moving around and only partly ordered. 2 - the cold smectic stage is closest to the solid phase where the molecules align themselves into tightly wound chiral matrixes.

Liquid crystal thermometers portray temperatures as colors and can be used to follow temperature changes caused by heat flow. They can be used to observe that heat flows by conduction, convection, and radiation.

Liquid crystals are very often used when someone is ill and for other medical reasons. They read body temperature by being placed against the forehead. Liquid crystals are safer than a mercury-in-glass thermometer, but don't always give an exact result, especially the smaller ones.

Liquid crystal thermometers are also commonly used in aquariums. [2]