Graphene lining doesn’t sound like a fashion statement, but it could prove its value when mosquitoes are about.
A US study suggests the newish nanomaterial (essentially a thin layer of graphite, the material used in a pencil) not only stops them biting you, it blunts their urge to even try.
According to researchers from Brown University, it appears to block the chemical signals mosquitoes use to sense that a blood meal is near.
“Mosquitoes are important vectors for disease all over the world, and there’s a lot of interest in non-chemical mosquito bite protection,” says Robert Hurt, senior author of a paper in the journal Proceedings of the National Academy of Sciences.
“We had been working on fabrics that incorporate graphene as a barrier against toxic chemicals, and we started thinking about what else the approach might be good for. We thought maybe graphene could provide mosquito bite protection as well.”
Finding out if it could required a mix of hi-tech and old school experimentation.
Hurt and colleagues created a fabric by covering cheesecloth in graphene oxide (GO) – a graphene derivative that can be made into films large enough for macro-scale applications.
They then asked three groups of volunteers to stick an arm into an enclosure full of lab-bred, disease-free mosquitoes. One group had a small patch of skin exposed, while the others had a similar patch covered in either GO or ordinary cheesecloth.
The outcome was striking. Those protected by GO didn’t get a single bite, while bare and cheesecloth-covered skin was feasted upon.
What was most surprising, however, was that the mosquitoes completely changed their behaviour near the GO-covered skin.
“With the graphene, the mosquitoes weren’t even landing on the skin patch: they just didn’t seem to care,” says lead author Cintia Castilho.
“We had assumed that graphene would be a physical barrier to biting, through puncture resistance, but when we saw these experiments, we started to think that it was also a chemical barrier that prevents mosquitoes from sensing that someone is there.”
To test this, they dabbed human sweat onto the outside of a graphene barrier. With the chemical cues on the other side of the graphene, mosquitoes flocked to the patch in much the same way they flocked to bare skin.
That’s a positive, as further tests showed that GO was a great physical barrier when dry but could be punctured by a mosquito’s proboscis when wet.
However, another form of GO with reduced oxygen content (called rGO) was shown to provide a barrier when both wet and dry.
The next step is to find a way to stabilise GO so it’s tougher when wet. It has a big advantage over rGO, Hurt says, because “GO is breathable, meaning you can sweat through it”.