Conditioner COVID catcher

Using hair conditioner to catch COVID before it infects people
22 June 2021

Interview with 

Jiaxing Huang, Northwestern University


Now “hairs” an interesting story: scientists have turned the conditioner you rub on your head into a covid-19 trap! Agents like the coronavirus that causes COVID-19 - in common with many other diseases like the flu - spread through liquid droplets that spray out from infected airways when we speak, cough, sneeze or even just breathe. Now researchers at Northwestern University have designed a surface coating, based on the chemicals used in hair conditioner, that can catch droplets that brush past the surface so they don’t bounce back into the air and infect someone. Adam Murphy heard how Jiaxing Huang made the jump from hair care to covid in the first place…

Jiaxing - Yeah, that's a nice coincidence there. Before the pandemic, part of my lab was actually doing hair dye research. So we had a chance to understand and learn a number of established chemistries in hair care. So when we try to find something to trap the aerosol droplets, one conclusion we, came to is that we need to find something that water droplets stick really well. Well, if you think about hair conditioner, one of the main ingredients in there is trying to coat the hair uniformly and then make the hair surface absorb moisture. So we thought that maybe that's something we can just start to try right away. In the first proof of concept, it was very straightforward. We have this polymer, you dissolve it in water, and we can make a paint. So you can then just spread it on the surface or you can brush coat it, or you can use a rod to spread it across a flat surface. In the next generation, we wanted to apply these to many different kinds of surfaces. So we decided to make the solution more versatile instead of treating existing surfaces to suit the coating solution, we want to make sure we have a solution that can work generically. And indeed, we can coat this material on wood, metal, plastic, textile, even concrete walls.

Adam - And then how does it actually work? What's going on that lets it stops the aerosols?

Jiaxing - A round droplet comes in, and when it hits the surface, it will flatten out into a pancake shape. But it doesn't stop right there because the droplets are somewhat elastic. It will contract and then bounce back or break up into small pieces. So the key here is the pancake stage. So that's a stage with an enormous contact area with the substrate. We thought that if we can make the substrate a little bit stickier so they can grab the pancake shape droplet, then you wouldn't be able to bounce back. That's sort of the first clue that's making it more water liking so it can glue to the water droplet better so that it can prevent them from bouncing away.

Adam - And how well does it work?

Jiaxing - It actually works quite well. We had a demonstration where we coat a plastic sheet and rolled up into a tube, and now we have these lab-generated aerosol steams and we pass them through the tube. Now without coating, you will see in just a few seconds, the aerosol streams will flow down the tube and escape. But with the coating, it actually lasts for much longer. You can wait for one or two minutes, with a continuous input of aerosol streams and barely anything comes out. So that's a strong indicator that all the droplets are captured.

Adam - Where would this go? What do you imagine this being used for in an ideal case?

Jiaxing - If you look around in your room, you actually see enormous areas of indoor surfaces, right? For example, a window and the window blinds, the ceiling and the wall. And most of these areas are what I call low touch or no touch areas. We're not going to touch those areas at all. So why don't we repurpose this idling surface and convert them into a passive aerosol absorption device,? In this way, if you have a lot of aerosol generators in a room - by the way, that's us; if we have a lot of people talking, singing in the room, we are excellent aerosol generators - so if we have these aerosols being generated indoors, then I'm hoping these surfaces can help to remove these aerosol droplets and reduce the concentration. So this will reduce the probability of infection. Now another, perhaps more immediate, use is that you can try to coat this material on transparent dividing barriers. So for example, plexiglass barriers that have become ubiquitous in this pandemic. You see them everywhere. So if we make the plexiglass droplet-absorbing, then we can not only protect you, we can also protect others around in the same environment.

Adam - What's stage are you at in its development? And what's the next thing to do.

Jiaxing - We were only able to test aerosol droplets, that were generated by lab apparatus, but I'm hoping that after this paper is published, it becomes open knowledge. And I would love to see people in other parts of the world, anywhere, feel free to pick it up and design your own human droplets trial. I don't think that's very difficult to do. I think you just need to go through the proper procedure and find the proper collaborator. And I'd love to see these being used.


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