Do you still remember the performance presented by Beijing Winter Olympics Organizing Committee at the closing ceremony of Pyeongchang 2018 Winter Olympics? The performance featured two impressive black technologies: smart ice screens with perspective display and graphene heated apparel. Graphene, seemingly advanced technology, is actually widely used as clothing material at first.
1. What is graphene?
Graphene is an allotrope of carbon consisting of a single layer of atoms arranged in a two-dimensional crystal. Two British physicists were awarded the Noble Prize in Physics in 2010 for the isolation and preparation of graphene. By far, graphene is believed to be the thinnest, strongest, lightest and the most flexible nanophase material.
Graphene is the best conductor of heat and electricity, a better material for barrier, and an ultra-thin, strong and stable material with better magnetism and transparency. Simply speaking, it is stronger than diamond, lower in electric resistance than silver and the best conductor of electricity and heat. Another notable property of graphene is that it is almost transparent, just like a piece of paper. Magic or not? It’s self-evident!
2. Why can graphene be used for heating?
As we said before, grapheme is the best conductor of electricity. When the positive and negative poles of the graphene heating film are charged, carbon molecules in the film begin to produce phonons, ions and electrons, and the motions (known as Brownian Motion) and fluctuations of carbon molecule groups generate heat. The heat is in turn emitted in a flat and even manner by limiting the wavelength of far infrared ray to 5-14 micrometers, which can be easily absorbed by human body, with the total effective heating conversion rate being as high as 99%. Moreover, due to grapheme’s superconductivity, the stability of the heating performance can be ensured.
In other words, grapheme is used as a carrier for the generation of heat, which is more effective than any known materials in the market. The heat generated can be easier to be absorbed by human body through controlling the radiation wavelength, and it can even offer physiotherapeutic effects (infrared ray physiotherapy). In the future, solar energy is likely to be used to generate thermal energy.
3. Is grapheme heating reliable?
For the time being, grapheme can only convert electricity to thermal energy. As a result, all kinds of grapheme heated products need electricity to work, making it necessary to take a portable power bank.
Unlike traditional electric resistance heating, grapheme is safer, and can still work in the event of being partially broken. Some grapheme apparel is advertised as being water washable because of its hydrophobicity. Since the producer is so confident about their products that you can wash it without worry.
However, due to the high cost of grapheme, plenty of products in the market are not necessarily use it as heating modules. Instead, manufactures use carbon fiber or nanometer, or even cheaper traditional wired heating chips. Among the three choices, carbon fiber is the most commonly used one because of its relatively low cost and more resemblance to grapheme in properties. However, carbon fiber has a fatal shortcoming: once it is bent and broken, electric resistance in the broken part will be reduced by dozens of times, which may lead to high temperature, scald, and even fire.
