Graphene, the high-tech substance that has shown promise for applications in electronics, solar cells and medicine, now has another use: hair colouring.

Key points: Naturally black graphene has been turned into a spray-on hair dye that is as permanent as conventional products

Naturally black graphene has been turned into a spray-on hair dye that is as permanent as conventional products Because graphene is a good electrical conductor, the dye reduces static flyaways

Because graphene is a good electrical conductor, the dye reduces static flyaways It has a potential application for wearable electronics, researchers say

Research published today in the journal Chem shows graphene has promise as a colourfast hair dye that reduces static flyaways and hair breakage.

Graphene is a super-strong substance made of a single layer of carbon atoms arranged in a honeycomb pattern.

It is excellent at conducting both heat and electricity and is super strong, leading scientists around the world to scramble to figure out how to apply it to energy storage, solar cells, display screens and more.

But only the highest quality graphene can be used for those products, said study lead author Jiaxing Huang from Northwestern University.

He started wondering if there could be a use for the lower quality, cheaper form, graphene oxide.

"It started as a Friday-afternoon experiment in my lab," Professor Huang said.

"Let's think about what are the most fundamental properties of graphene? For graphene sheets, regardless of what kind of quality you have, the baseline property is that no matter what you do, you have black."

The group developed a water-soluble form of graphene oxide that could be sprayed onto the hair, combed through and dried to achieve the same colour quality and colourfastness as conventional permanent hair dyes in just a few minutes.

And because the graphene dye creates a physical coating on the hair rather than relying on chemical reactions to change the colour, it's less damaging to the hair than conventional dyes.

Back up. How does normal hair dye actually work?

Zoom right into a single strand of hair and you'll see it's not as smooth as you might expect, but covered in tiny scales.

Hair seems fairly smooth but its surface is actually coated in tiny scales. ( Getty: Kateryna Kon/ Science Photo Library )

Conventional permanent hair dyes use alkaline substances like ammonia to swell and separate these scales and diffuse the natural pigment in the hair so the artificial pigments can penetrate deeply, said Antonelle Lindrea, a hairdressing educator at Victoria University.

Because these chemical reactions change the structure of the hair to deposit the colour, permanent dyeing can weaken hair, making it more prone to breaking.

Ammonia can give off dangerous fumes, and dyes containing the substance can damage the hair, however ammonia-free products often contain ethanolamine, a known irritant, Ms Lindrea said.

Conventional hair colours often contain other irritants such as resorcinol, which can help achieve certain hair colours and helps bond dyes to the hair, and other substances that can cause allergic reactions, including the rare but life-threatening anaphylactic shock.

What makes this graphene dye different?

With the graphene colour, sheets of the substance coat the hair rather than penetrating it, meaning the hair is not damaged and reactive chemicals are not used.

The graphene oxide particles are very thin and very wide, like a sheet of newspaper, ideal for wrapping around and sticking to a hair.

Graphene's chemical structure means it produces a better black and is gentler on hair than conventional dyes. ( Supplied: Jiaxing Huang )

"If you think about a flat sheet and a round particle, the flat sheet will certainly like to stick to a surface a lot better. So this makes them a very good coating material on soft biological surfaces like a hair surface," Professor Huang explained.

Most coating-based dyes, like carbon black powders, are problematic because they wash out easily, Professor Huang said.

But when their solution of graphene sheets, chitosan polymer and vitamin C was applied to human hair samples, they were able to turn platinum-blonde hair black and keep it that way for at least 30 washes — the number necessary for a hair dye to be considered "permanent."

Even though the dye coats the hair, it doesn't add much bulk, thanks to the microscopic thinness of the graphene sheets.

"To put it in perspective, typically your hair is about 50 to 100 microns thick, and on top of that we're just adding another two microns, so just a few per cent."

For those familiar with sitting for hours in a salon chair to achieve that perfect shade, perhaps the most welcome news is that the graphene dyeing process only takes about 10 minutes.

The water-based graphene dye is sprayed onto the hair, combed through to be sure the hair is coated evenly, and then either air dried or blow dried.

Graphene oxide starts as colourless or light brown and darkens when heated, irradiated with UV light or when it reacts with a chemical like vitamin C.

Black is the easiest shade to achieve, but it can be used to create shades from light brown through to black, and could even create a gradient or "ombre" effect, where the hair starts dark at the roots and lightens toward the ends.

The other benefit Professor Huang and his team identified was reducing static flyaway hair, thanks to graphene's natural electric conductivity.

"Graphene oxide is not very conductive, but for static dispersal purposes it's enough," he said.

But even though the team has discovered a new solution for keeping dark hair sleek, it's still just a lab experiment, so you won't find it in your hair salon any time soon.

You mentioned something about high-tech applications?

While the study looked specifically at dyeing hair, the authors hinted that the technique could be used for more than just beauty products.

The authors say the dye's static reducing qualities may be of use in livestock farming and developing humanoid robots.

"For example, they could be applied to coat animal furs to reduce electrostatically induced irritation in livestock farming," the authors wrote.

"Antistatic hair would also be useful for the development of humanoid robots to reduce the level of static interruption to embedded electronics."

As well as dispersing electric charge, conductive hair could be used to collect charges to charge up a wearable electronic device, Professor Huang said.

"I think it would be a smaller scale, like charging up a human-machine interface," he said.

"This is a crazy idea, we haven't demonstrated it yet, but I think it's doable."

Professor Huang acknowledged hair dye was an unusual interest for a materials chemist who's spent a decade studying a substance usually associated with futuristic electronics. But he hoped it would inspire people to look to daily life to find problems and solutions worth investigating.

"There are a lot of research problems worth pursuing all around you," he said.

"[This hair dye] is related to health, it's related to personal expression, it's related to the environment."