Thermochromic Mechanisms Explained

There are two main ways to produce a thermochromic effect. The first is through the use of liquid crystals. Thermochromic crystals have very specific molecular structures depending on their temperature, and therefore rearrange themselves in different ways as the temperature changes. As these crystals rearrange, so does the way they reflect light and color. The other involves chemicals that change color depending on temperature, where microcapsules containing a chemical rupture when they pass a certain thermal threshold before changing color. The mechanism is a scientific marvel, but it is the application of such thermochromic elements that is fun and surprising. These are some of the best applications of the thermochromic material.

Thermochromic Dyes

These tints can be applied to any variety of materials and have a low threshold for color changes, making for a very dynamic transformation. Thermochromic dyes with a low threshold can be printed on T-shirts, leading to color changes depending on body temperature, exposure to sunlight, etc., producing a tie-dye effect that can be very visually striking or a more dramatic change. subtle, depending on the contrast. of the thermochromically activated layer and of the original color.

thermochromic layering

Thermochromism does not always have to be a change between two colors. It can also consist of a change between a color and a transparency, which has been used in practical applications such as new-to-market printing cards. These cards are marketed for their “personality”, in which handprints can be left on a surface, exposing a colorful background against a white foreground. Actually, a thermochromic layer is placed over an image. Heat from a human hand activates the chemical, which then changes to a transparency.

Thermochromic paper

Thermochromism is not limited to just fun/aesthetic purposes. Thermochromic paper demonstrates the business utility of thermochromic materials. Thermal printers can produce a high resolution image on chemically treated paper. Thermal barcode printers are the most common application. Chemically treated paper is fed into the printer before a thermal head is used to produce an image on the paper. As the microelements are rapidly heated and cooled in the thermal printer head, they are exposed to produce black on white (sometimes red, depending on chemical treatment). For example, a Zebra ZM400-2001-0100T thermal printer is capable of producing hundreds of labels in a completely inkless thermochromic process. In such applications, thermochromism allows for a more efficient and cleaner printing process.