"Your ring has changed color!"

"Because I'm in a bad mood! Don't mess with me!"

One kind of ring does change color, especially when people's emotions fluctuate. This kind of ring is called "mood ring", and it turns to red and sometimes blue when worn on the hand, which looks very magical. Does the mood ring really understand our mind and perceive our mood?

As early as the 1970s, the slightly mysterious trinkets such as "mood ring" appeared on the market, and there are still many shops selling such gadgets. Does mood ring colors really have something to do with mood? In fact, the so-called "mood ring" changes color according to changes in body temperature. The ring surface of the mood ring is made of thermosensitive color-changing materials such as liquid crystal or tombarthite. When the temperature changes, the molecular arrangement of the liquid crystal material or the energy transfer efficiency in the tombarthite material will also change, and eventually the color of the material will change. During the entire changing process, the material molecule itself has not changed, this is a physical changing process.

But our mood change is a complicated chemical changing process. From a physiological and psychological perspective, changes in mood need to be regulated by hormones, such as phenylethylamine, dopamine, adrenaline and so on. Some of these hormones make your heart beat faster, and some send a message of excitement and joy.

There is a certain relationship between emotions and body temperature. When we experience excitement, tension, anger, and sadness, body temperature will change. For example, excited emotions will increase body temperature, and sad emotions will decrease body temperature. The mood ring colors are based on this principle. This ring will change color when worn on the hand, and the color changing process is quite gorgeous.

Although they have been called "mood rings", these rings can only reflect the same thing: the temperature of the surrounding environment. The key to the "mood ring" discoloration is the thermochromic material encapsulated in a transparent shell. Specifically, it is a thermochromic liquid crystal material. Liquid crystal is a state between solid and liquid. In this state, although the molecules in the liquid crystal material are not arranged neatly like solid crystals, they are also more orderly than ordinary liquids. For example, the molecules may be arranged layer by layer and have a certain directionality. The "mood ring" uses a cholesteric liquid crystal material, which has the property of changing color with temperature.

The molecular structure in liquid crystal is affected by temperature, and the wavelength of light reflected by the material changes accordingly, so it displays different colors. This process has nothing to do with "mood". Although emotion may indeed change the body surface temperature a little, it is too inaccurate to infer the emotion from the temperature, and it can only be entertained at most.

In addition to liquid crystals, there are also some thermochromic materials that use chemical principles to change color by changing chemical balance and the structure of dye molecules. However, the discoloration of this material is usually only a switch between the two colors, and the response to temperature is not as sensitive as the liquid crystal material, and it does not have such a rich color-changing effect.