Liquid crystal thermometer

For example if the thermometer is put onto someone's forehead, it will change colour depending on the temperature of the person's body.

In medical applications, liquid crystal thermometers may be used to read body temperature by placing them against the forehead.

These are safer than a mercury-in-glass thermometer[citation needed], and may be advantageous in some patients, but do not always give an exact result, except for the analytic liquid crystal thermometer which shows the exact temperature between 35.5 and 40.5 °C (96–105 °F).

Liquid crystal thermometers are also commonly used in aquariums,[2] in homebrewing,[3] and in mood rings.

The liquid crystal thermometer was invented by Bob Parker in California, one of many of the inventor's thermochromic applications patented in the 1970s.