Thermochromic Mechanisms Explained

There are two primary 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 thus rearrange themselves in different ways as temperature changes. As these crystals rearrange, so too does the way they reflect light and color. The other involves chemicals which change color depending on temperature, wherein micro capsules containing a chemical rupture when passing a certain thermal threshold before changing color. The mechanism is a scientific wonder, but the application of such thermochromic elements is what is both fun and surprising. Here are some of the best applications of thermochromic material.

Thermochromic Dyes

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

Thermochromic Layering

Thermochromism doesn’t always need to be a change between two colors. It can also consist of a change between a color and a transparency, which has been utilized in practical applications such as the new-to-market Print cards. These cards are marketed for their “personality”, wherein hand prints can be left on a surface, exposing a colorful background against a white foreground. In reality, a thermochromic layer is placed over an image. The heat of a human hand activates the chemical, which then shifts to a transparency.

Thermochromic Paper

Thermochromism isn’t just restricted to fun/aesthetic purposes. Thermochromic paper proves the business utility of thermochromic materials. Thermal printers are able to produce a high resolution image on chemically treated paper. Thermal barcode printers are the most common application. The chemically treated paper is fed into the printer before a thermal head is used to produce an image on the paper. As micro elements rapidly heat and cool on the thermal printers head, an exposure is made to produce black on white (sometimes red, depending on the chemical treatment). For example, a ZM400-2001-0100T Zebra 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.

Source by David D Westgrove

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