In order to eliminate static electricity, I painted the wall at the door black...

On winter nights, workers who are eager to go home after get off work are always "surprised" by static electricity at the door. Every time you touch the door handle, it's like a little adventure. The slight stinging from your fingertips makes you pull your hand back. In order to open the door smoothly, people have come up with various "tactics": touching the wall, putting batteries in your pocket, using various "static removal tools"... just to resolve this silent "battle". Static electricity is like a winter urchin, adding a little trouble to people's lives.

Image source: Photo Network

01

How is static electricity generated?

There are many reasons for the generation of static electricity, and the static electricity phenomenon we feel in our daily lives is mainly due to "frictional electrification".

Matter is made up of atoms, and atoms are made up of nuclei and electrons. There is an attraction between the positively charged nuclei and the negatively charged electrons, and electrons are usually bound around the nuclei. Since the number of positive and negative charges in atoms is generally equal, objects are not charged.

Image source: Photo Network

However, different types of atoms have different abilities to bind electrons. When two different objects rub against each other, electrons will transfer from atoms with weak binding forces to atoms with strong binding forces, thus forming a charged area on the surface of the object. For example, when you use a plastic comb to comb your hair, the electron transfer will cause an imbalance in the charge on the surface of the object, thus showing a charged nature. This is the process of static electricity generation.

Image source: Photo Network

So, why does static electricity always cause us the trouble of being shocked by electric shocks in our daily life?

In fact, this is the discharge process of static electricity. When a hand with static electricity approaches a metal door handle, many electrons in the metal will be attracted by the charge on your fingertips and move closer to your hand, and an electric field will be established between your finger and the door handle. Due to the tip discharge effect, the charge will gather at the fingertips, and the closer the fingertips are to the door handle, the stronger the electric field will be. Eventually, the electric field will be strong enough to break through the air, forming a strong instantaneous current. The discharge process will produce noise and sparks, and the current will act on the nerve endings of the fingers, causing us to feel pain.

Image source: Photo Network

The generation of static electricity has a lot to do with humidity. In summer, the humidity is relatively high, and the water molecules in the air can transfer part of the charge faster through contact with clothing, reducing the accumulation of static electricity; in winter, it is relatively dry, which is not conducive to the transfer of static electricity, so we are easily "electrified".

02

Is static electricity dangerous?

The static discharge time generated by human body contact is very short, so it is harmless to the human body.

However, in other places, the harm of static electricity cannot be underestimated. For example, precision electronic equipment is particularly afraid of static electricity, and thousands of volts of static electricity may break down components.

In addition, oil pipelines and oil tankers must also eliminate static electricity, because the friction between gasoline and the pipe wall will generate static electricity. If it is not eliminated in time, the sparks generated by accidental discharge will cause explosions. Therefore, there is a small tail behind the oil tanker - the static belt, which hangs to the ground, the purpose of which is to conduct static electricity to the ground.

Image source: Photo Network

03

What are some ways to eliminate static electricity in life?

Methods to eliminate static electricity can be summarized into two categories. One is to reduce the generation of static electricity from the source, such as: increasing air humidity, choosing clothes that are not easy to generate static electricity; the other is to release static electricity indirectly, such as: touching walls, keys and other objects.

(1) Increase humidity

Increasing humidity can effectively transfer the accumulated charge on the body and significantly reduce static electricity. The common static spray on the market also uses a similar principle. Its ingredients contain cationic surfactants, which can also play a role in neutralizing charges.

Wet your hands with water or a wet towel, or wipe the surface of your clothes with a wet wipe to release static electricity.

Image source: Photo Network

Especially for those who love cats and dogs, do you always feel "electrically shocked" when petting them in winter?

This is because animal hair is particularly easy to become electrically charged due to friction in a dry environment, and if you encounter these naughty and playful creatures, they can end up like the one below if you are not careful.

Image source: Xiaohongshu netizens

You can try putting a humidifier in the room, wash your hands before petting your pet, use an anti-static comb to smooth your pet's fur, and use pet wipes to moisten their fur to reduce static electricity on your pet.

(2) Choose clothes that are not prone to static electricity

In winter, static electricity is particularly easy to be generated when putting on and taking off clothes, which has a lot to do with the fabric of the clothes. In winter, people wear more wool sweaters and down jackets. If you look closely at the fabric composition of down jackets, you will find that they are basically polyester fibers, which is what we often call polyester.

Fabric composition of a down jacket

Image source: provided by the author

Polyester fiber and wool are particularly prone to generating static electricity after friction, because the surface of polyester fiber is a hydrophobic structure, which is not easy to retain water molecules and has poor conductivity.

Image source: https://www.mdpi.com/2310-2861/9/2/109

The figure below is an electrostatic sequence (a sequence of substances arranged from positively charged to negatively charged). The farther apart the materials are, the easier it is for them to be electrified by friction.

Image source: https://zhuanlan.zhihu.com/p/32244204

It can be seen that wool and polyester are far apart in the static sequence diagram, so there is more static electricity after friction. If a layer of cotton clothing is added between the sweater and the down jacket, the static electricity will be greatly reduced, because cotton has good moisture absorption, whether it is rubbed with wool or polyester fiber, less static electricity is generated. At the same time, adding some softener when washing clothes can also effectively reduce static electricity.

In addition, in order to prevent the annoying static electricity from occurring at the source, a type of clothing with antistatic effect has also appeared on the market. Antistatic agent (surfactant) is applied or sprayed on the surface of the fabric. The antistatic agent gives the material surface a certain lubricity and reduces its friction coefficient, thereby inhibiting or reducing the generation of static charge.

Image source: Photo Network

(3) Discharge static electricity through other objects

Touching the wall is a typical way to release static electricity, because the wall can conduct static electricity away from the human body. When the human body touches the wall, the charge of the human body can be grounded by touching the wall, thereby releasing the charge carried, reducing the possibility of static electricity being generated again when touching other objects. The larger the area of ​​the hand touching the wall, the better the effect.

In addition, holding a conductive object such as a metal key in your hand can transfer the charge of your body to the key, and then release it to other objects through the key, which can also achieve the effect of eliminating static electricity. Static eliminators purchased online also use a similar principle.

Image source: Photo Network

04The purpose of static electricity

Although static electricity brings some troubles to our lives, it actually has many uses and can benefit mankind.

Electrostatic copying: Using the surface of a photosensitive material with static electricity, when exposed, the local charge changes accordingly with the intensity of the light, thereby retaining the image, and then absorbing toner and transferring it to paper.

Electrostatic dust removal: Using the electrostatic field to charge dust particles in the gas and adsorb them. It is used to purify gas or recover useful dust particles in metallurgy and chemical industry.

Electrostatic spraying: Use high voltage electric field to charge the paint and adsorb the paint particles on the surface of the workpiece. The advantages are high efficiency and material saving.

In short, static electricity is a ubiquitous natural phenomenon that is both interesting and mysterious. By understanding the principles and causes of static electricity, we can master the methods of eliminating static electricity, better understand and utilize this phenomenon, and apply static electricity technology to life.

Next time you go to open a door, remember to touch the wall first!

References

[1] Shen Ganqing. Use silicone to soften wool textiles with caution - Study on the electrostatic phenomenon of wool textiles [J]. Wool Textile Science and Technology, 2005(02):5-8. DOI:10.19333/j.mfkj.2005.02.001.

[2] Ji Yuan. Research on the trial production and application performance of antistatic agent PEEJ for polyester[D]. Donghua University, 2006.

[3] Sfameni S, Lawnick T, Rando G, Visco A, Textor T, Plutino MR. Super-Hydrophobicity of Polyester Fabrics Driven by Functional Sustainable Fluorine-Free Silane-Based Coatings. Gels. 2023; 9(2):109. https://doi.org/10.3390/gels9020109

[4] Is static electricity on fabrics in winter all due to chemical fibers? Let’s find out - Zhihu https://zhuanlan.zhihu.com/p/32244204

[5] What is the principle of static electricity in textiles, and to what extent are common fabrics prone to static electricity? - Zhihu https://www.zhihu.com/question/54124761

Author: Jade Cucumber loves to eat potato chips and is often electrocuted

Editor: Tiara

Acknowledgements: Guo Weihong, PhD, senior engineer at the University of Chinese Academy of Sciences, provided scientific guidance for this article